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Transfusion 231 > Week 1 > Flashcards

Week 1 Flashcards

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1
Q

What is immunohematology

A

study of blood as it relates to AG and AB

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2
Q

Why are screen performed on patients

A

to detect allo AB in patients plasma sample so you know what crossmatching procedure needs to be done to cross match units for the pt

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3
Q

What are the blood products that transfusion department issues

A

packed red cells, fresh frozen plasma, platelets, fibrinogen
concentrates, and any factor concentrates main goal is to give ABO compatible blood but sometimes you cant

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4
Q

What is the primary immune response

A

Humoral with B lymphs
-after a transfusion B lymphs recognize AG on red cells through B receptors and AB production may not start

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5
Q

What is humoral immunity

A

-fluid parts of the immune system like AB and complement components
-mediated by B cells
-initiate AB production
-AB produced by B cells

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6
Q

What is cellular immunity

A

Mediated by T Cells and Lymphokines (activates/deactivates cells)

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7
Q

What is the function of the AB

A

to bind foreign molecules -AG
-AG are found on the surface of the foreign cells
-one AB binds with one AG (epitope)
-study of AB -AG reactions = serology

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8
Q

What are AG

A

-what the body thinks is foreign and causes the body to produce AB
-large molecular weight proteins and polysaccs
-on surface of cell membrane or integral part of cell membrane
-determined by inheritance

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9
Q

What is Antigenicity

A

Ability of antigen to be recognized by antibodies

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10
Q

What does antigenicity depend on

A

Chemical Composition and Complexity – Proteins are the best immunogens (produces immune response). Can be protein, glycolipid, glycoprotein, lipoprotein, nucleic acid
Degree of Foreignness – Greater the difference has a greater chance of producing a reaction
Molecular Weight – Larger molecular weight are better immunogens
Dosage and Antigen Density – Number of cells and amount of antigen introduced
Route of Administration – Intramuscular or intravenous

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11
Q

What are AG composed of

A

Protein
glycolipid - (carb and lipids)
glycoprotein (carb and protein)
lipoprotein
nucleic acid

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12
Q

What are AG composed of

A

Non- ABO like Rh/Kell =proteins
ABO = carbs

Lewis AG are soluble substances in plasma so they are absorbed into the membrane

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13
Q

Difference between protein and carb AG

A

Protein Antigen – Integrated into the RBC membrane, developed at birth
Gene codes directly for protein (Rh, Kell, Kx, Deigo)

2.Carbohydrate Antigen – found on Surface of the RBC membrane
Gene codes for an enzyme like glycosyltransferase which adds sugar to a precursor on RBC membrane to form AG
-enzyme production starts early but AG not developed at birth
-ABC AG similar structure to pollen or bacterial membrane

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14
Q

Why Testing Cord/Baby Samples May Have Weak Reactions

A

Antigens are NOT well developed – Despite enzyme production beginning early

Wharton’s Jelly (substance surrounding umbilical cord) can interfere with testing

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15
Q

What are AB

A

proteins produced by B lymphs because there was stimulation by AG
-Immunoglobulins
-Gamma globlin region in SPE
-isotypes/classes depend on Heavy chain
-specificity based on variable regions
-IgG, IgM, IgA, IgD, and IgE
Allo antibodies are antibodies to a foreign antigen of the same species
* Autoantibodies are antibodies to an antigen one possesses

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16
Q

What sites does the AG bind

A

AB binds the specific antigen
* Fc Portion determines the antibody function and contains the complement
binding region and the cell activation region

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16
Q

What is the structure of the AB

A

2 Heavy chains + 2 Light chains – Can either be in constant or variable region

Fab region + Fc region – Fab (Binds antigen), Fc (determines antibody function, contains complement binding region and cell activation region)

-IgG – 2 binding sites; temperature: most optimal at 37 deg C- can cross placenta HDFN may need enhancement techniques
-IgM – 10 binding sites; most optimal at 4 deg; pentamer
Can cause immediate transfusion reaction

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17
Q

Types Of Exposure To Antigens

A

Naturally Occurring (Non Red Cell Immune) – After birth or throughout life; Exposure to antigen similar to RBC antigen
Red Cell Immune – Through transfusion or pregnancy; Exposure to antigen on foreign RBC

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18
Q

how does a B cell respond to an AG

A

-AG stimulates lymphs with best fit receptor . Lymphs signalled to produce B cell clone >plasma cells > ONE ab with ONE specificity

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19
Q

Types of Antibody Production Response

A

Primary Antibody Response – Formation of IgM, followed by IgG and memory B cells
-peak response is smaller with low affinity 5-10 days
–more memory cells produced and response sustained for longer

Secondary Antibody Response – more production of IgG and less IgM; Faster and increased potential for RBC destruction > Leads to plateau
-in 1-3days
-higher average affinity

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20
Q

What does the likelihood of an immune response depend on

A

-immunogenicity of the AG - able to stimulate an immune response
-pt own immune systems sensitivity- some people develop multiple AB from ONE transfusion
-iron supplements are given to pt to raise hgb instead of transfusing

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21
Q

Types of AG exposure

A

-AB formation can occur without apparent AG exposure- naturally occurring (ABO groups)
- can occur after birth “Naturally occuring”
-AG on foreign RBC
-through transfusion or pregnancy = Red Cell Immune

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22
Q

What happens after AB production

A

AB binds to specific AG
-AG (donor RBC) are targeted for destruction
-IgM INTRAvas clearance
-IgG EXTRAvas clearance

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23
Q

What is the complement pathway

Study These Flashcards
A

-activated proteins in immunological reactions
-activation occurs as cascade
-proteins circulate in inactive state but activate and convert into active enzymes

24
Types of complement pathways
Classical Pathway – Activated by presence of antibody bound to an antigen Alternative Pathway – Activated by bacteria, viruses, foreign constitutes
25
Main Components of Complement Cascade
-C3 convertase (C4b2a)- -C5 convertase (C4b2a3b) -C3a: anaphylatoxin, eosinophil chemotaxin -C3b: mediates phagocytosis, opsonin -C5a: anaphylatoxin & chemotaxin for leukocytes and monocytes -C5b-9: Membrane Attack Complex (MAC - C4b2a3b)
26
What is the classical pathway composed of
C1 complex C2b and C4b C3 convertase
27
What is the alternative pathway composed of
C3 hydrolysis C3b and C3a -C3b cleaves C5 into C5a/b and then C5B- C9 come together from MAC attack
28
Detection of Complement –
Anti-C3d tests for C3d (breakdown of C3b) because C3b and 4b are left behind on the RBC membrane and degraded into C3D/4D -AB can dissociate while complement portions stay on the red cell -Pos reactions are helpful in transfusion
29
Where does INTRAvas occur , what does it involve, lead to
Occurs in the veins, arteries, capillaries -Involves IgM to detect ABO -Complement cascade leads to MAC formation, then hemolysis
30
Where does EXTRAvas occur , what does it involve, lead to
-Occurs in the spleen and liver -Involves IgG to detect Rh -Complement cascade stops at C3b (no MAC forms). Splenic macrophages detect Fc of IgG
31
Serology – Antigen and Antibody Reactions SOURCE of AG source of AB detection
Source of antigen – Patient Source of antibody – Donor’s plasma or commercially prepped antisera Detection of reaction – Hemolysis (these are rejected) or Agglutination
32
What tubes are preferred for blood bank
lav or pink top -(Lavender Tubes) EDTA – Chelates Ca2+ and prevents the vitro activation of the complement pathway; Preferred for RBC and Plasma
33
Types of Antigen and Antibody Reactions Sensitization
Antibody binds to Antigen epitope >> Invisible Dependent on temperature, incubation time, pH, ionic strength
34
Types of Antigen and Antibody Reactions Precipitation –
Precipitation – Soluble antigens >> Visible
35
Types of Antigen and Antibody Reactions Agglutination –
Agglutination – Lattice formation occurs (involves IgM pentamer) >> Visible Dependent on zeta potential which affects crosslinking, zone of equivalence, centrifugation -to decrease zeta potential isotonic saline, albumin, LISS, PEG, AHG and enzymes in testing.
36
Types of Antigen and Antibody Reactions Hemolysis
Hemolysis – Complement is activated >> Visible
37
What are potentiators
Used to decrease zeta potential aka enhances antibody reactions (such as albumin, LISS, PEG, AHG, enzymes in testing)
37
Factor Affecting Antigen and Antibody Reactions Type of immunoglobin
-immunoglobin IgG or IgM -RBC Solution – Suspension material, pH -Concentration of antigen and antibody, Cell to serum ratio Prozone – Antibody excess Equivalence Zone – Proper proportion of antibody and antigen Post Zone – Antigen excess -temps -time = increased incubation can cause AB to dissociate -size, shape or charge
38
Affinity Factor Affecting Antigen and Antibody Reactions
strength of the binding between a single antibody and an epitope of an antigen.
39
Avidity: Factor Affecting Antigen and Antibody Reactions
overall strength of the reaction depends on the affinity of the antibody, valency and noncovalent attractive forces
40
What is zeta potential
Net negative charge around the RBC repelling each other Too much zeta potential = No agglutination IgM is a pentamer and can cause agglutination because it can bridge the gap; IgG is too small
41
How to decrease zeta potential?
Increase protein to reduce the positive and negative ions that prevent antibodies from binding with antigens
42
how can enzymes enhance AB reactions
Can either enhance antibody reactions OR depress reactivity of other antibodies (such as Ficin, Papain, Trypsin, Bromelin)
43
how can we make AB-AG reactions more visible
goal is to enhanceAB uptake and make reaction visible -ALB reduces repulsion between cells making the agglutination more visible to the eye -PEG increases detection sensitivity LISS – Used for screening cells; Speeds up agglutination, economical, provides good sensitivity but can enhance cold autoantibodies
44
During agglutination how is testing prepped
Packed RBCs are DILUTED -3-5% suspension is needed -Plasma and Antisera are NOT dilutedW
45
What is the Immediate Spin (Direct Antiglobulin Test - DAT) technique entail
Detects in vivo antibody or complement that’s attached to RBC membrane -Detects IgM (ABO/Rh) -add plasma w/3-5 % RBC -reagent is monoclonal -AB from Hybridoma
46
What is the Antiglobulin Test (Indirect Antiglobulin Test - IAT) technique entail
Detects in vitro antibody or complement that’s attached to RBC membrane -Detects IgG -add plasma w/ 3-5% red cells -incubate, wash and add AHG, centrifuge and read -needs to be incubated at for sensitization to occur
47
What is the Antihuman Globulin (AHG) Reagent
helps with the detection of AG and AB reaction; contains AB to target human AB Polyspecific AHG Reagents – Anti-IgG and Anti-C3d Monospecific AHG Reagents – ONLY Anti-IgG or ONLY Anti-C3d
48
How to Perform DAT (IS)
Mix plasma (antisera; antibody) with 3-5% RBCs (antigen). Centrifuge.
49
How to Perform IAT
IS Phase – Mix 2 drops plasma (antisera; antibody) with 1 drop 3-5% RBCs (antigen). Centrifuge. Record at IS and RT. Sensitization may have occurred here. Incubate at 37C – Centrifuge and record at 37C. Wash with saline 3 times – Removes free antibody from the mixture Add AHG – Agglutination will occur with sensitization occurred. Centrifuge. Read at AHG ***If negative – Add Coombs Control Cells (CCC)/Check Cells (RBCs coated with sensitized IgG antibodies; will react with AHG > produce Positive Result)
50
What is the Antiglobulin Reagent
-human IgG is injected into rabbit to produce human AB -uses an AB against a human to help with AB-AG detection -the human AB is the AG -sometimes the AG-AB dont have bridging to produce agglutination so the AHG gives the complex a bridge and helps to form a lattice making the reaction visible
51
When will we see a positive IAT test
-if AB is in the plasma and sensitization occurs - AB attaches to RBC+AG -Add AHG = agglutination IF there is sensitization = POSITIVE
52
When will you see a true negative IAT
NO AB in the plasma -add AB -no agglutination -if reaction is negative add CCC which binds with AHG -CCC needs to be added to validate the test
53
What happens if there was AB in the plasma but washing did not occur properly
-unbound AB binds with AHG and neutralizes = no agglutination and free AB not bound to RBC are in the test mixture (prozone phase) -false neg
54
Coombs Control Cells CCC
-controls with AB on RBC -helps tell the difference between true neg and false neg -addtion of AHG if the reaction is negative under the mic, CCC is added to make sure
55
No Antibody is detected and negative results under the microscope
-Add CCC -agglutination occurs -Reaction with CCC and AHG Confirms a TRUE Negative IAT
56
No Reaction after CCC is added Indicates a false Negative IAT.
AHG was Neutralized Must Repeat Testing

Transfusion 231 (10 decks)

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