Genetics and Immunology

Question 1

The use of EDTA plasma prevents activation of the classical complement pathway by_____________.

a. causing rapid decay of complement components
b. chelating Mg ions which prevents the assembly of C6
c. chelating Ca ions which prevents assembly of C1
d. Enhancing the actions of C1 inhibitor

Answer 1

c. chelating Ca ions which prevents assembly of C1

The classical pathway is one of three activation pathways of the complement system, which is a major contributor to the defense of infections, clearance of pathogens, removal of apoptotic/nectrotic cells, and maintenance of hemeostasis.

The classical pathway is activated by an antigen-antibody reaction. The binding of C1q initiates teh sequential activation of the eleven proteins. The classical pathway has a clacium-dependent step (C1q, C1r, C1s).

EDTA anticoagulant chelates Calcium ions (Ca+) so that the classical complement cascade cannot initiate.

In the IRL serum (red top not containing EDTA) is sometimes preferred as complement dependent antibodies can be detectable!

Question 2

The expected frequency of an inherited gene combination is 35%. Population testing reveals that the observed frequency of the same gene combination is 55%. This is an example of:

a. Independent segregation
b. Hard-Weinberg Law
c. Crossing Over
d. Linkage Disequilibrium

Answer 2

d. Linkage Disequilibrium

Linkage Disequilibrium, which is when two genes are inherited togetehr more often that expected statistically

Question 3

In a given population, 16% of individuals are tested as Rh-. What is the gene frequency of the D antigen?

a. 0.4
b. 0.6
c. 0.16
d. 0.32

Answer 3

b. 0.6

We know that 15% of teh population is dd (D-). The square root of 0.16 is 0.4, which is the frequency of d gene. Remember that p+q = 1.0, or that the frequency of teh two genes is equal to 100% so, we know that q is 0.4 from above. Therefore, 1-q=p or 1-0.4=0.6

Frequency of D gene is 0.6 or 60%

Question 4

A father carries the Xg^a trait and passes it on to all of his daughters but none of his sons. What type of inheritance does this represent?

a. Autosomal dominant
b. X-Linked dominant
c. X-Linked recessive
d. Autosomal recessive

Answer 4

b. X-Linked dominant

We know this because only the daughters are affected. Autosomal inheritance would show equal distribution between sons and daughters. Also we know it has to be dominant. Girls inherit two X chromosomes, so a recessive trait would not display unless both parents had the trait. We would also not see a 100% inheritance rate for the girls.

Question 5

Restriction endonucleases characteristically function by:

a. promoting digestion of RNA
b. cleaving DNA into smaller fragments
c. terminating translation of mRNA
d. removing histones from the DNA strands

Answer 5

b. cleaving DNA into smaller fragments

Restriction endonucleases are derived from bacteria and function by cleaving DNA at specific sequences. Molecular scientists use this concept to remove a segment of DNA in a predictable, controlled fashion and “paste” it into another segment. They can also use the action of specific endocuclease enzymes to recognize a specific DNA sequence.

It is because these enzymes were discovered that scientists were able to develop the Restriction Fragment Length Polymorphism (RFLP) method of molecular testing.

Question 6

The portion of the immunoglobulin molecule that determines class is the:

a. light chain
b. kappa chain
c. lambda chain
d. heavy chain

Answer 6

d. heavy chain

It is the heavy chain portion of the Ig that determines class.

Question 7

Which statement best describes the process of mitosis?

a. Cell division by which only one half of the daughter cells produced are identical to the parent cell.

b. Cell division of germ cells by which two successive divisions of the nucleus produce cells that contain half the number of chromosomes of somatic cells.

c. Cell division that produces four daughter cells having the same number of chromosomes as the parent.

d. Cell division that produces two daughter cells with the same number of chromosomes as the parent cell.

Answer 7

d. Cell division that produces two daughter cells with the same number of chromosomes as the parent cell.

Question 8

When a recessive trait is expressed:

a. One gene carrying the trait was present.

b. Two genes carrying the trait were present.

c. No gene carrying the trait was present.

d. The gene is hemizygous.

Answer 8

b. Two genes carrying the trait were present.

Question 9

In a pedigree analysis, which statement about the symbols used is true?

a. Deceased family members have a line crossed through the symbol.

b. A consanguineous mating is indicated by a simple line between a male and female.

c. The propositus is always found in the last generation on the pedigree.

d. A still birth is indicated by a triangle.

Answer 9

a. Deceased family members have a line crossed through the symbol.

Question 10

Which of the following nitrogenous bases make up DNA?

a. Adenine, Leucine, Guanine, Thymine.
b. Adenine, Cytosine, Guanine, Thymine.
c. Adenine, Lysine, Uracil, Guanine.
d. Adenine, Cytosine, Guanine, Thymine.

Answer 10

d. Adenine, Cytosine, Guanine, Thymine.

Question 11

Mutations can occur following DNA replication that escapes the proofreading and repair systems, Which statement about DNA mutations is true?

a. All mutations result in a phenotypic change.
b. A frameshift mutation at the beginning of the coding sequence is most likley to result in a phenotypic change.
c. A transversion always encodes for a stop codon.
d. A missense point mutation never encodes for a stop codon.

Answer 11

b. A frameshift mutation at the beginning of the coding sequence is most likley to result in a phenotypic change.

Question 12

Which phenotype would be expected from the mating of a Jk (a+b-) female and a Jk (a-b+) male?

a. Jk (a+b-)
b. Jk (a+b+)
c. Jk (a-b+)
d. all of the above.

Answer 12

b. Jk (a+b+)

Question 13

Which statement describes an intron?

a. The part of a gene that contains nonsense mutations.
b. The coding region of a gene.
c. The noncoding region of a gene.
d. The resting stage between cell divisions.

Answer 13

c. The noncoding region of a gene.

Question 14

Which statement about isolation of nucleic acids is true?

a. All isolation methods involve the use of organic solvents.
b. High protein concentration increase the DNA yield.
c. mRNA can be effectively isolated with the use of poly-A-coated beads.
d. Silica particles bind DNA under high salt concentrations.

Answer 14

d. Silica particles bind DNA under high salt concentrations.

Question 15

The purpose of transcription is to:

a. Produce a protein
b. Read the mRNA by the ribosome.
c. Synthesize RNA using DNA as a template.
d. Replicate DNA.

Answer 15

c. Synthesize RNA using DNA as a template.

Question 16

When a male possesses a phenotypic trait that he passes to all his daughters and none of his sons, the trait is said to be:

a. X-linked dominant
b. X-linked recessive
c. Autosomal dominant
d. Autosomal recessive

Answer 16

a. X-linked dominant

Question 17

When a female possesses a phenotypic trait that she passes to all of her sons and none of her daughters, the trait is said to be:

a. X-linked dominant
b. X-linked recessive
c. Autosomal dominant
d. Autosomal recessive

Answer 17

b. X-linked recessive

Question 18

Which statement correctly describes DNA replication in eukaryotes?

a. Semionservative replication from RNA; requires DNA polymerase.

b. Bidirectional replication; requires RNA primer.

c. Conservative replication fro DNA; requires RNA polymerase.

d. Occurs at the replication fork; both strands replicated in the same direction.

Answer 18

b. Bidirectional replication; requires RNA primer.

Question 19

How is tRNA different from other types of RNA?

a. It has a 3’ poly-T tail.
b. The immature form contains introns.
c. It has a 3’ methylated cap.
d. It recognizes amino acids and nucleic acids.

Answer 19

d. It recognizes amino acids and nucleic acids.

Question 20

Which statement about translation of proteins is false?

a. It occurs on the ribosomes in the cytoplasm of the cell.

b. Post-translation processing can include glycosylation.

c. mRNA delivers the amino acids to the growing peptide chain during elongation.

d. The codon UAA would terminate translation.

Answer 20

c. mRNA delivers the amino acids to the growing peptide chain during elongation.

Question 21

The pattern of inheritance most commonly expressed by blood group genes is:

a. X-link recessive
b. Autosomal recessive
c. Autosomal codominant
d. X-linked codominant

Answer 21

c. Autosomal codominant

Question 22

Macrophages and monocytes have receptors for which portion of the IgG molecule?
a. Fab
b. Fc
c. Hinge region
d. J chain

Answer 22

Correct: Fc

Macrophages and monocytes have receptors for the Fc portion of the IgG molecule. The Fc portion of the IgG molecule will be sticking up away from the RBC membrane allowing for complement fixation and monocyte binding. In an extravascular hemolytic transfusion reaction, RBCs are coated with IgG antibodies. When these sensitized RBCs move through the spleen, the macrophages will attach to the sensitized RBCs via the Fc receptors, and the coated RBCs will be removed from circulation.

The Fab portion of the IgG will bind to the specific corresponding antigen on the RBC membrane (Fab=antigen binding)
The hinge region is part of the Fc fragment and contains disulfide bonds
The J chain is present in IgM and dimer/trimer forms of IgA molecules to hold them together

Question 23

A woman is in her 28th week of pregnancy. She is typed as group O Negative with a negative antibody screen. Rh immune globulin (RhIg) is administered. One week later the antibody screen is repeated and an anti-D reacting 2+ with D+ cells is detected.

What type of immunity is this?

a. Natural Acquired Active Immunity
b. Natural Acquired Passive Immunity
c. Artificial Acquired Active Immunity
d. Artificial Acquired Passive Immunity

Answer 23

Correct: Artificial Acquired Passive Immunity.

Natural immunity occurs when the patient is exposed to antigens as they exist in the environment.

Natural ACTIVE immunity = develop antibody after exposure to disease or foreign RBC. This happens as a result of just living in the world.
Natural PASSIVE immunity =antibodies are transferred from one person to another by natural means. Example: Pregnancy, in which certain antibodies are passed from the maternal blood into the fetal bloodstream in the form of IgG.

Artificial immunity occurs when the body is given immunity by intentional exposure to small quantities of it.

Artificial ACTIVE immunity = antibodies formed in response to an antigen, something intentionally induced in the patient, from a source, that was manufactured.  Example: Vaccine.
Artificial PASSIVE immunity = patient receives complete antibodies in the form of an injection. The patient does not elicit an immune response because the complete antibody can remove the offending antigen. Example: RhIg or Hepatitis B Ig.

Question 24

A serum sample is suspected of containing an IgM antibody. The serum is treated with DTT and the following results are obtained:

DTT treated serum + RBC = negative

Untreated serum + RBC = positive

What conclusion can be drawn from these results?

a. The serum contains an IgM antibody
b. The serum contains an IgG antibody
c. The serum contains both IgG and IgM antibody
d. The serum contains neither IgG nor IgM antibody

Answer 24

Correct: Serum contains an IgM antibody.

DTT (Dithiothreitol) dissolves IgM antibody disulfide bonds and eliminates activity of the antibody whereas IgG antibodies are generally unaffected.

When answering this question, pay close attention to whether the serum or cells are being DTT treated. Had this been an IgG antibody, both the DTT treated and the untreated serums would have been positive.

In the reference lab, we can also use DTT to destroy antigens, such as Kell system antigens.

Question 25

A patient is suspected of having Paroxysmal Cold Hemoglobinuria (PCH). The physician orders a Donath Landsteiner test be performed. The technologist obtains a fresh EDTA sample from the patient for use in testing. He sets up the test as follows: Tube Result Tube 1: Patient plasma incubated at 4C only No Hemolysis Tube 2: Patient plasma incubated at 37C only No Hemolysis Tube 3: Patient plasma + fresh plasma incubated at 4C then 37C No Hemolysis Assume that proper controls were also tested. What conclusion can be drawn from these results? a. Patient does not have the Donath Landsteiner antibody b. Patient DOES have the Donath Landsteiner antibody c. No conclusion-this is not the proper test for PCH diagnosis d. No conclusion-the test was not set up properly.

Answer 25

Correct: No conclusion-the test was not set up properly. In order for hemolysis to occur, there must be a source of fresh complement in the test system. Normally Donath Landsteiner testing is performed with a patient SERUM sample that is < 4 hours old. Serum has active complement because there is no chelation of calcium ions and can activate the complement cascade, causing hemolysis. Complement is only stable at 4C for about 48 hours but should be tested as soon as possible. In EDTA plasma, the calcium is chelated by the anticoagulant which prevents complement activation so hemolysis is possible. SBB exam: Always make a note of the factors that go into testing before making a decision on the appropriateness of testing, as well as the interpretation of results.

Question 26

A patient is transfused two units of RBCs without incident. 2 years later, the patient is transfused with two units of RBCs, without any evident complications. 6 days after the transfusion, the patient appears to have a delayed hemolytic transfusion reaction due to anti-Jka. The immune system concept that best describes this incident is: a. innate immunity b. passive immunity c. primary immune response d. secondary immune response

Answer 26

Correct: Secondary Immune Response The patient was exposed to Jka+ RBCs in the first transfusion episode. This is the primary stimulation to the antigen. At the second transfusion, the patient is exposed a second time, and the memory cells trigger production of anti-Jka, which then binds with the transfused cells causing a delayed hemolytic transfusion reaction. Innate immunity is a nonspecific, system which attempts to prevent sensitization altogether. Passive immunity is conferred when an individual is given antibodies passively, to prevent his/her own immune system from being stimulated to produce antibodies (example: RhIG). Primary immune response occurs when the antigens are much more immunogenic, and it happens with the first exposure to the antigen.

Question 27

When monitoring the severity of HIV cases, patients will be tested for a ratio of T helper cells to T cytotoxic cells. In a normal individual, the ratio should be greater than 1.0. As HIV disease progresses into full blown AIDS, the ratio drops below 1.0. In this scenario, which cell marker would be used to measure the T Helper cells? a. CD3 b. CD4 c. CD8 d. CD34

Answer 27

Correct: CD4 CD3 occurs on both T helper and T cytotoxic (suppressor) cells CD8 occurs on T cytotoxic cells CD34 occurs on hematopoietic stem cells

Question 28

In a given population, 16% of individuals are tested as Rh negative. What is the gene frequency of the D gene? a. 0.4 b. 0.6 c. 0.16 d. 0.32

Answer 28

This is calculated as follows. In the Hardy Weinberg equation, p(2) + 2pq + q(2) = 1.0 p2 = DD genotype 2pq = Dd genotype q2 = dd genotype We are told that the Rh- population is 16% or 0.16, the Rh-population is dd genotype. If q2 = dd genotype, then q2 = 0.16 Take the square root of q2 (0.16) to get the gene frequency q. The square root of 0.16 is 0.4. If p + q = 1.0, then 1.0 - q = p, and 1.0 - 0.4 = 0.6 So therefore the frequency of the D gene is 0.6 There is no d gene, nor is there a d antigen. We used the lower case d to designate a chromosome which lacks the D antigen.

Question 29

What is the minimum number of IgG molecules required to activate Complement Protein C1? a. One b. Two c. Three d. Four

Answer 29

The C1 component of complement is the first step to activation via the classical pathway. Activation of the classical pathway is caused by immunoglobulins interacting with the target antigen. C1 binds to the two or more Fc portion of immunoglobulins. IgG molecules are small, and therefore a minimum of two molecules are required to activate C1. IgM is a larger, pentameric (5 armed) molecule, so only one IgM molecule is needed to activate C1.

Question 30

A group A patient is transfused with 50cc of group AB RBCs and has an immediate hemolytic transfusion reaction. Which of the statements below best explains the cause of this severe reaction? a. The patient developed IgG anti-B in response to previous RBC transfusions, and this antibody caused intravascular hemolysis. b. The patient's naturally occurring IgG Anti-B caused intravascular hemolysis. c. The patient developed IgM anti-B in response to previous exposure to group B RBCs, and the antibody caused intravascular hemolysis. d. The patient's naturally occurring anti-B caused intravascular hemolysis

Answer 30

Correct: The patient's naturally occurring anti-B caused intravascular hemolysis Recall that ABO antibodies are naturally occurring and not immune stimulated. IgM antibodies cause intravascular hemolysis and IgG antibodies cause extravascular hemolysis. It takes only ONE IgM molecule to stimulate the complement cascade, whereas it requires two IgG molecules. Because IgG molecules coating RBCs are typically too far apart to trigger the complement cascade, IgG coated cells are removed extravascularly by the MPS (Mononuclear Phagocyte System, formerly RES)

Question 31

Interleukin-2 (IL-2) is produced by which of the cells below? a. Activated T cells b. Dendritic cells c. B cells d. All of the above

Answer 31

Correct: All of the above IL-2 is a cytokine that is involved in proliferation and regulation of T cells. In terms of transfusion medicine, IL-2 helps to regulate the function of distinguishing between self and non-self. Low levels of IL-2 can result in activated T cells attacking self, resulting in autoimmune disease.

Question 32

The frequency of the Jka gene is 0.52 and the frequency of the Jkb gene is 0.48. What is the frequency of the Jk(a+b-) phenotype? a. 27 b. 20 c. 48 d. 52

Answer 32

Correct: 27% Answer is calculated as follows using Hardy Weinberg equation, p2+ 2pq + q2= 1.0 p2 = JkaJka genotype (phenotype would be Jk(a+b-) pq = JkaJkb genotype (phenotype would be Jk(a+b+) q2 = JkbJkb genotype (phenotype would be Jk(a-b+) We are given the gene frequency of the JK*A gene as 0.52. This would be "p" in the equation p+q=1 Now we want to to find p2= (.52)2 answer is .27 or 27% SBB exam: It may be that the choices given for answers do not match exactly the percentage. If that is the case, pick the answer that is the closest. This will be on your exam!

Question 33

What is the process by which one of the copies of the X chromosome is inactivated? a. Meiosis b. Mitosis c. Y Inactivation d. Lyonization

Answer 33

Correct: Lyonization Lyonization, or X Inactivation, is when most of the genes in one of the two X chromosomes in the female somatic cell are inactivated during early development. The maternal or paternal X chromosome may become inactivated. X-borne genes that encode for blood groups: XG and XK XG escapes inactivation because of it's location on the extreme tip of the X chromosome Inactivation of XK gene leads to the McLeod phenotype which lacks Kx and therefore reduced expression of Kell antigens

Question 34

A patient has anti-E, anti-K, and anti-Jka in their serum. The doctor is requesting 3 units for transfusion. Calculate the number of units that will need to be tested. a. 20 b. 15 c. 45 d. 51

Answer 34

Correct: 20 1) Know each antigens frequency: E = 29, K = 9, Jka = 77 2) Figure out the prevalence of units negative for each antigen: E - = 71, K - = 91, Jka - = 23 3) Multiply the percentage of negative donors expressed as a decimal (Number calculated in step 2, divided by 100) together: 0.71 (E-) x 0.91 (K-) x 0.23 (Jka-) = 0.15, or 15% This means about 15 units out of 100 units screened will be negative for that combination. 4) 3 units are needed. 3 units needed/0.15 = 20 units screened SBB Exam: If race is not specified, the frequencies used should be calculated based on the predominant race found in the donor population. It may be that the choices given for answers do not match exactly the percentage. If that is the case, pick the answer that is the closest. The above frequencies are from Harmening. AABB Tech Manual lists Jka as 76% frequency, which would mean 19 units would need to be screened. The SBB exam in recent years DID give percentages to use in these calculations BUT you will still need to know frequencies to answer other questions.

Question 35

Which of the following is not a secondary lymphoid organ? a. Spleen b. Thymus c. Lymph Nodes d. Liver

Answer 35

Correct: Thymus The thymus and bone marrow are primary lymphoid organs. B and T cells mature in these organs. The lymph nodes, spleen, and mucosa-associated tissue are secondary lymphoid organs. These are the sites of cell function for B and T cells.

Question 36

What is the most common nucleotide change affecting the expression of a blood group antigen? a. Deletions b. Single Nucleotide Polymorphism c. Insertions d. Errors in DNA Replication

Answer 36

Correct: Single Nucleotide Polymorphisms (SNPs) Most polymorphic blood group antigens are the result of SNPs.

Question 37

Which IgG subclass is the most efficient at initiating the classic complement cascade? a. IgG1 b. IgG2 c. IgG3 d. IgG4

Answer 37

Correct: IgG3 IgG3>IgG1>IgG2 IgG4 does not activate classic complement but it can activate via the alternate pathway Kidd antibodies are predominantly IgG3.

Question 38

A trait that is carried on the Y chromosome will be passed from: a. Fathers to all of their sons and daughters b. Fathers to half of their sons and daughters c. Fathers to all of their sons and no daughters d. Fathers to all of their daughters and no sons

Answer 38

CORRECT: Fathers to all of their sons and no daughters If the trait is carried on the Y chromosome, females cannot carry the trait because they have two X copies. The father has to give Y to his sons so they will carry the trait, daughters get the father's X so they will not have the trait.

Question 39

A man whose genotype is BO has a child with a woman that is OO. What is the probability that their first child will be group B? a. 25% b. 50% c. 75% d. 100%

Answer 39

CORRECT: 50% O is recessive, B is dominant

Question 40

What are MHC Class II antigens found on? a. Platelets b. Red Cells c. Dendritic Cells d. Nucleated Cells

Answer 40

CORRECT: Dendritic Cells MHC Class II are located on most antigen presenting cells, which includes dendritic cells. MHC Class II genes code for HLA-DR, HLA-DQ, and HLA-DC antigens. MHC Class I are located on most nucleated cells and platelets. MHC Class I genes code for HLA-A, HLA-B, and HLA-C antigens. Both classes are important to detect foreign substances and the immune reactions against them.

Question 41

What is the most common inheritance pattern for blood group systems? a. Dominant b. Co-Dominant c. Recessive d. Amorphic

Answer 41

CORRECT: Co-Dominant Dominant: gene product is expressed over another gene Co-Dominant: equal expression of both traits Recessive: observed when not paired with a dominant allele Amorphic: gene that doesn't express a detectable product

Question 42

What is the half-life of IgG? a. 2-3 days b. 21 days c. 15 days d. 5 days

Answer 42

CORRECT: 21 days IgG has a half-life around 21 days. Depending on the reference, IgG may be listed as having a half-life between 21-25 days, be more conservative if using for a calculation, e.g. how long will RhIG remain in the system after X weeks? (IgG3 has a half-life of 7-8 days but only makes up 4-7% of the total IgG in serum and therefore not used. )

Question 43

Steric exclusion of water molecules is the mechanism of which enhancement? a. Polyethylene Glycol (PEG) b. Low Ionic Strength Saline (LISS) c. 22% Albumin d. Papain

Answer 43

a. Polyethylene Glycol (PEG)

Question 44

Which of the following is a structure located within the cell nucleus that carries genes in a linear order as a part of the DNA molecule? a. Antigen b. Karyosome c. Chromosome d. Locus

Answer 44

c. Chromosome

Question 45

What component of the Hardy-Weinberg equation (p2 + 2pq + q2) signifies heterozygotes? a. p^2 b. 2pq c. q^2 d. none of the above

Answer 45

b. 2pq

Question 46

How many chromosomes does the developing child normally carry? a. 23 b. 46 c. 16 d. 32

Answer 46

b. 46

Question 47

What is the statistical basis of the Hardy-Weinberg principle? a. Selection of mates is dependent on blood types and therefore is random. b. Selection of mates is dependent on blood types and therefore is biased. c. Selection of mates is independent on blood types and therefore is random. d. Selection of mates is independent on blood types and therefore is biased.

Answer 47

c. Selection of mates is independent on blood types and therefore is random.

Question 48

What is the basic unit of inheritance that determines the production or nonproduction of specific markers? a. Antigen b. Chromosome c. Gene d. Locus

Answer 48

c. Gene

Question 49

What is the major constituent of chromosomes? a. Golgi Bodies b. Mitchondria c. RNA d. DNA

Answer 49

d. DNA

Question 50

Population studies reveal that 27% type Jka negative. What is the gene frequencies of Jka in this population? a. 0.48or 48% b. 0.50 or 50% c. 0.28 or 28% d. 0.80 or 80%

Answer 50

p2 + 2pq + q2 = 1; p + q = 1 p = gene freq. of Jka; q = gene freq. of Jkb q2 = 0.27; p = 0.48 (Jka) q = 0.52 (Jkb) 2pq = 0.50 Jk(a+b+)

Question 51

A 56 year old female with cold hemagglutinin disease has a positive direct antiglobulin test (DAT). When the DAT is repeated using monospecific antiglobulin sera, which of the following is most likely to be detected. a. IgM b. IgG c. C3d d. C4d

Answer 51

c. C3d This patient has a cold hemagglutinin, so complement (or C3d) would be the most likely to be detected coating the RBCs. The antibody is most likely IgM but the antiglobulin reagent does not detect IgM. Polyspecific detects IgG and C3d only.

Question 52

Which of the following samples for blood bank testing is MOST likely to contain active complement? a. EDTA-anticoagulated sample b. Heparin-anticoagulated sample c. Serum sample stored at 4C for 72 hours d. Serum sample drawn 2 hours ago

Answer 52

Correct: Serum sample drawn 2 hours ago If you need the specimen to have active complement, then collect serum and use it as soon as possible. Complement is only stable at 4C for about 48 hours, so the specimen drawn in serum and kept for 72 hours at 4C is unacceptable. Anticoagulated specimens do not have adequate levels of calcium, magnesium, or both due to the actions of the anticoagulants. Specifically, EDTA will totally obstruct complement activation. Heparin prevents complement activation because it inhibits the cleavage of C4. As an aside, most blood banks prefer to use anticoagulated specimens for testing so that complement does not bind in-vitro, causing false results in testing. Also does not require waiting for the specimen to clot before using it.

Question 53

A patient was transfused two units of RBCs without incident in 2019. 2 years later, the patient is transfused with two units of RBCs, again without any evident complications; however, 6 days after the transfusion the patient appears to have a delayed hemolytic transfusion reaction due to anti-Jka. The immune system concept that best describes this incident is: a. Innate Immunity b. Passive Immunity c. Primary Immune Response d. Secondary Immune Response

Answer 53

Correct: Secondary Immune Response. Primary Immune Response: The response to the immune system to an antigen (immunogen) that leads to induced sensitivity. The response after the initial antigenic exposure is detectable only after a lag period of several days to a couple weeks. When the patient was exposed to Jk(a)+ RBCs in the first transfusion episode, the immune system had a primary stimulation to the antigen. Secondary Immune Response: Upon a subsequent stimulus by the same antigen, the immune response is more rapid than in the case of the primary. At the second transfusion, the patient is exposed a second time to Jk(a)+ red cells and the memory B cells trigger the production of anti-Jka, which then binds with the transfused cells causing a delayed hemolytic transfusion reaction. Innate Immunity: A nonspecific system which attempts to prevent sensitization altogether and can come into action soon after a foreign antigen's appearance. These mechanisms include physical barriers such as skin, chemicals in the blood, and immune system cells that attack foreign cells in the body. Passive Immunity: Conferred when an individual is given antibodies passively to prevent their own immune system from being stimulated to produce antibodies, a common example is Rh Immune Globulin.

Question 54

A patient is given IVIG (IV Immunoglobulin). This is an example of: a. Active Immunity b. Passive Immunity c. Naturally Occurring Antibodies d. Vaccination

Answer 54

Correct: Passive Immunity Passive immunity occurs when an individual is given antibodies in order to fight infection or prevent sensitization. Active immunity occurs when an individual is exposed to a foreign substance, and his immune system actually produces antibodies specific to the foreign antigen. Naturally occurring antibodies do not require previous sensitization in order to be present. Most people with healthy immune systems are expected to present with naturally occurring ABO antibodies appropriate for their ABO type. Vaccination is a treatment that uses your body’s natural defenses to build resistance to specific infections and makes your immune system stronger.

Question 55

A patient produces an IgG anti-Fya. What portion of the immunoglobulin molecule is responsible for binding specifically to the Fy(a) antigen on RBCs? a. Fc Fragment b. J Chain c. Hinge Region d. Fab Fragment

Answer 55

Correct: Fab Fragment When an immunoglobulin molecule is cleaved, three portions are produced. One Fc fragment, and two Fab fragments. The Fab fragments are specific to one antigen. In this case, they would be specific to the Fy(a) antigen.

Question 56

The presence of bacteria, fungi, parasites, and tumor cells might activate the complement cascade via which pathway? a. Alternative Pathway b. Classical Pathway c. Both the alternative and classical pathway d. Neither the alternative nor classical pathway

Answer 56

Correct: Alternative Pathway Polysaccharide and liposaccharides, such as those found on the surfaces of Bacteria, fungi, tumor cells, can activate complement via the alternative pathway. The classical pathway is activated by the binding of C1 to the Fc fragment of IgM or IgG molecules

Question 57

When monitoring the severity of HIV cases, patients will be tested for a CD4/CD8 ratio. In a normal individual, the CD4/CD8 ratio should be greater than 1.0 (Know this!). As HIV disease progresses into full blown AIDS, the CD4/CD8 ratio drops below 1.0. In this scenario, the CD4 value represents a measure of: a. T Suppressor Cells b. B Cells c. T Helper Cells d. Interleukin 1

Answer 57

Correct: T-helper Cells The T helper cells are positive for CD4, and the T suppressor cells are positive for CD8. If the amount of T helper cells is too low, then the immune system can not function properly because there is not enough stimulus. CD stands for "clusters of differentiation". These are specific markers on the surface of T cells.

Question 58

Antibodies are secreted by _________ cells. a. T helper Cells b. T suppressor Cells c. Plasma Cells d. Antigen-Presenting Cells

Answer 58

Correct: Plasma cells Plasma cells are mature B cells which make large amounts of antibody in a soluble form.

Question 59

Granulocyte Macrophage -Colony Stimulating Factor (GM-CSF) is a substance which is sometimes given to granulocyte donors in an attempt to stimulate the donor's immune system to produce more granulocytes. GM-CSF is an example of ____________? a. T helper cell b. B cell c. Cytokine d. Phagocyte

Answer 59

Correct: Cytokine Cytokines are soluble substances that mediate the immune response. Some cytokines, such as GM-CSF, will encourage the immune response while other cytokines, such as Interleukin-10, have a suppressive effect.

Question 60

A group O patient is given 50cc of group A red blood cells and has an immediate severe hemolytic transfusion reaction. In this case, the hemolysis was most achieved via which complement pathway? a. Classical b. Alternative

Answer 60

Correct: Classical The anti-A,B and anti-A in the group O recipient attached to the A antigen on the donor RBCs and initiated the complement cascade via the Classical pathway. ABO antibodies are IgM and have the pentamer form which can easily bind and activate the Classical pathway much quicker and more efficiently than IgG.

Question 61

Macrophages and monocytes have receptors for which portion of the IgG molecule? a. Fc b. Fab c. Hinge Region d. None-macrophages and monocytes do not have receptors for IgG molecules.

Answer 61

Correct: Fc portion Macrophages and monocytes have receptors for the Fc portion of the IgG molecule. The spleen has macrophages, which destroy old, deformed and sensitized RBCs. In an extravascular hemolytic transfusion reaction, RBCs are coated with IgG antibodies. The Fab portion of the IgG will bind to the specific corresponding antigen on the RBC membrane (the Fc portion of the IgG molecule will be sticking up away from the RBC membrane). When these sensitized RBCs move through the spleen, the macrophages will attach to the sensitized RBCs via the Fc receptors, and the coated RBCs will be removed from circulation. RBCs sensitized with IgG antibody with Fab portion attached to antigen on the membrane, Fc portion extending outward that can attach to monocytes and macrophages to be removed from circulation.

Question 62

MHC Class II antigens are found on most of which kind of cells? a. Nucleated Cells b. Dendritic Cells c. Hematopoietic Stem Cells d. Antigen Presenting Cells

Answer 62

Correct: Antigen Presenting Cells The Major Histocompatibility (MHC) antigens are important in recognizing foreign substances and the immune reaction against them. MHC Class I antigens are found on nucleated cells (except sperm or trophoblasts) and play a critical role in cytotoxic T-Cell function. MHC Class II antigens are found on most antigen-presenting cells (B Cells, activated T Cells, and dendritic cells). Note dendritic cells would not be wrong above, but there is a better answer. The HLA system will be covered in more depth later in the semester.

Question 63

What is the half-life of IgG? a. 3 days b. 6 days c. 10 days d. 21 days

Answer 63

Correct: 21 days IgG has the longest half-life of the immunoglobulins at 21 days. The next closest is IgA at 6 days, followed by IgM at 5 days.