Trans Lecture 4 Flashcards
Rh blood group system (191 cards)
1
Q
How many genetic loci determine the Rh System Inheritance?
A
Two genetic loci determine the Rh System Inheritance.
2
Q
During which period was the inheritance of the Rh Blood Group System in question?
A
The inheritance of the Rh Blood Group System was in question from the 1940s to the 1990s.
3
Q
Which terminology is commonly used today for the Rh System Inheritance?
A
The terminology that is part of the Fisher-Race Theory is most commonly used even today.
4
Q
How are genes coding for the Rh system inherited?
A
Genes coding for the Rh system are inherited as haplotypes, which are close together on the same chromosome.
5
Q
How many genes are closely inherited on the same locus?
A
Three genes are closely inherited on the same loci.
6
Q
How can you predict the probability of D-positive offspring?
A
You can predict the probability of D-positive offspring from a D-negative mother and a heterozygous father.
7
Q
Is the gene ‘d’ a real gene in Rh System Inheritance?
A
No, the gene ‘d’ does not exist and is used only for illustrative purposes.
8
Q
What percentage of children could be D-positive when the mother is D-negative and father is heterozygous?
A
50% of the children could be D-positive.
9
Q
What is the purpose of giving Rogan to Rh- mom?
A
The purpose is to prevent complications during pregnancy and childbirth.
10
Q
When is Rogan given to Rh- mom?
A
Rogan is given to Rh- mom at 28 weeks of pregnancy.
11
Q
How many weeks are there in a full-term pregnancy?
A
There are 40 weeks in a full-term pregnancy.
12
Q
When is Rogan given to Rh- mom after birth if the baby is Rh+?
A
If the baby is Rh+, Rogan is given to the mom within 3 days of birth.
13
Q
According to the Fisher-Race theory, how are the D, C, and E genes inherited?
A
D is inherited at one locus, C or c is inherited at a second locus, and E and e are inherited at the third locus.
14
Q
How many gene complexes are there at the Rh locus according to Fisher-Race?
A
There are 8 gene complexes at the Rh locus according to Fisher-Race.
15
Q
What is the order of gene notation according to Fisher-Race?
A
Fisher-Race uses DCE as the order for gene notation.
16
Q
What is the difference between Wiener and Fisher-Race theories in terms of Rh System Inheritance?
A
The difference is the inheritance of the Rh system on a single gene locus vs 3 separate genes.
17
Q
According to Wiener, how many alleles are there for the Rh antigens?
A
According to Wiener, there are 8 alleles resulting in various Rh antigens.
18
Q
Is the Wiener terminology used as often today?
A
No, the Wiener terminology is not used as often today.
19
Q
What do you often see when a person is considered Rh-positive?
A
You often see Rho(D) when a person is considered Rh-positive.
20
Q
What do immunohematologists use when recording most probable genotypes?
A
Immunohematologists use combinations of both Fisher-Race and Wiener systems.
21
Q
How should you convert a Fisher-Race notation into Wiener notation?
A
To convert a Fisher-Race notation into Wiener, you should write R0 for Dce.
22
Q
What is the genotype for the most common D-positive genotype?
A
The most common D-positive genotype is R1r, which is DCe/dce (antibody E-).
23
Q
What is the genotype for the most common D-negative genotype?
A
The most common D-negative genotype is rr, which is dce/dce.
24
Q
What does ‘R’ indicate in the context of Rh System Inheritance?
A
‘R’ indicates Rh positive.
25
What does '(r)' indicate in the context of Rh System Inheritance?
'(r)' indicates Rh negative.
26
What can cause red cells to agglutinate?
Red cells can agglutinate when they are pre-sensitized with antibody in vivo and brought close together in a high protein medium.
27
Can red cells with a positive DAT agglutinate in a high protein medium?
Yes, red cells with a positive DAT can agglutinate in a high protein medium.
28
What can cause a false positive in D typing?
If red cells already have antibody on them, the high protein in the anti-D can bring the cells close together, forming cross-bridges and causing a false positive result.
29
How can the Rh(D) type be determined if the Rh control is positive?
If the Rh control is positive, the Rh(D) type must be determined using a low protein anti-D serum.
30
What is the composition of saline anti-D?
Saline anti-D contains IgM anti-D suspended in a protein concentration of about 6 - 8% albumin.
31
When is saline anti-D usually used?
Saline anti-D is usually used to D type red cells that give a positive Rh control when tested with slide and modified tube anti-D or cells with a positive DAT.
32
Why is saline anti-D considered an expensive antiserum?
Saline anti-D is considered expensive because donors producing IgM anti-D are hard to find.
33
Can saline anti-D be used for weak D (Du) typing?
No, saline anti-D cannot be used for weak D (Du) typing as it is IgM and weak D typing requires IgG.
34
What are the characteristics of chemically modified anti-D?
Chemically modified anti-D contains IgG anti-D that has been chemically modified to increase the span of its Fab fragments and a low protein concentration of 6 - 8%.
35
How is chemically modified anti-D made?
Chemically modified anti-D is made by treating IgG anti-D with sulfhydryl agents to split the interchain disulphide bonds and allow wider distance agglutination.
36
What can serve as a control for chemically modified anti-D typing?
The forward ABO group or an Rh control of 6% albumin can serve as a control for chemically modified anti-D typing.
37
When is monoclonal/polyclonal anti-D used?
Monoclonal/polyclonal anti-D can be used as an alternative to saline anti-D for typing red cells with a positive DAT, for routine D typing, and for weak D (Du) typing.
38
What are the characteristics of monoclonal/polyclonal anti-D?
Monoclonal/polyclonal anti-D blends contain monoclonal IgM and polyclonal IgG anti-D, and require 6% albumin as an Rh control.
39
What reagent has replaced saline anti-D?
Chemically modified reagent has replaced saline anti-D for typing red cells with a positive DAT.
40
Why is a control necessary in Rh typing?
A control is necessary because heavily sensitized red cells may spontaneously agglutinate even in low protein media, such as is present in anti-A, anti-B, and saline anti-D.
41
What is the most common position effect in weak D caused by?
Weak D caused by C inherited in trans.
42
What happens to D-antigen expression when the D and C genes are inherited on the opposite chromosome?
The D-antigen expression will be weaker.
43
What are the two types of weak D?
CIS and TRANS.
44
What happens in CIS weak D?
Both genes are inherited on the same chromosome.
45
What happens in TRANS weak D?
The genes are inherited on different chromosomes.
46
Why would today's weak D type as a regular D?
Due to the sensitivity of the monoclonal reagents.
47
What is an example of CIS Du?
Phenotype R1r’ (CDe/Ce).
48
What is an example of TRANS Du?
Phenotype R0r’ (cDe/Ce).
49
What gene takes over in TRANS Du?
The C gene takes over.
50
What is weakened in TRANS Du?
The D antigen.
51
What is missing in weak D-Mosaic/Partial D?
Some components of the D antigen are missing.
52
What happens if a patient with weak D is transfused with D positive blood?
They may develop an anti-D alloantibody to the missing part of the antigen.
53
What may happen if anti-D reagents from 2 different manufacturers do not agree?
Suspect partial or mosaic D.
54
Why should weak forms of D antigen be investigated in blood donors?
They are substantially less immunogenic than normal D positive blood.
55
What is standard practice for transfusion in Rh-negative donors?
To investigate all blood donors for weak D or all first-time Rh-negative donors.
56
What should be done if a weak D is positive in blood donors?
The units should be labelled as Rh Positive.
57
What does weak D cause in patients with anti-D?
Severe hemolytic transfusion reaction (HTR).
58
What can blood recipients with weak D develop when transfused with D positive blood?
An anti-D alloantibody to the missing part of the antigen.
59
What happens if the direct agglutination test with commercial anti-D is negative for weak D?
No longer common practice to investigate for a possible weak D.
60
How are patients with weak D typically typed?
As Rh negative and will receive Rh negative blood.
61
What are compound antigens in the Rh system?
Antigens that occur when two alleles are inherited on the same gene.
62
What is an example of a compound antigen in the Rh system?
f (ce), r1 (Ce), cE, CE.
63
What happens if an individual has an anti-f?
It would only react with f positive cells and not cells positive for c or e in trans.
64
What is the significance of f cells in testing for compound antigens?
They are clearly marked on the antigram of screen and panel cells.
65
What is a cis-product antigen?
The product of two alleles inherited on the same gene.
66
How many compound antigens are there in the Rh system?
There are 4 compound antigens.
67
What is the significance of antibodies to compound antigens?
They may be useful in ascertaining the exact Rh genotype.
68
How does testing the father's Rh genotype help predict HDN likelihood?
Testing the father's Rh genotype helps predict the probability of the baby being D positive and suffering from Rho HDN.
69
What is the probability of a baby being D negative if the father is also D negative?
If the father is D negative, the baby will also be D negative with a 0% probability of suffering from Rho HDN.
70
What is the probability of a baby being D positive and suffering from Rho HDN if the father's Rh genotype is R1r, R2r, or Ror?
If the father's Rh genotype is R1r, R2r, or Ror, the baby has a 50% probability of being D positive and suffering from Rho HDN.
71
What is the probability of a baby being D positive and suffering from Rho HDN if the father's Rh genotype is R1R1, R2R2, R1R2, RoRo, R1Ro, or R2Ro?
If the father's Rh genotype is R1R1, R2R2, R1R2, RoRo, R1Ro, or R2Ro, the baby has a 100% chance of being D positive and suffering from Rho HDN.
72
What type of antibodies are Rh antibodies?
Rh antibodies are commonly IgG antibodies.
73
How are Rh antibodies formed?
Rh antibodies are formed by immune stimulus such as transfusions or pregnancy, and are not naturally occurring.
74
What enhances the agglutination of Rh antibodies?
Agglutination of Rh antibodies is enhanced by high protein (albumin), low-ionic strength saline (LISS), proteolytic enzymes (ficin), and polyethylene glycol (PEG).
75
Which cells do Rh antibodies react stronger with - homozygous or heterozygous cells?
Rh antibodies react stronger with homozygous cells than with heterozygous cells, showing dosage.
76
What is the most common Rh antibody seen in Rh positive individuals?
The most common Rh antibody seen in Rh positive individuals is anti-E.
77
Which Rh antigen is difficult to find compatible blood for due to anti-e autoantibody presence?
Anti-e is difficult to find compatible blood for since 98% of the population have the e antigen.
78
Which Rh antibodies are often seen in combination?
Anti-C,e or Anti-c,E are often seen in combination.
79
What is the purpose of Rh immune globulin (RhIG)?
Rh immune globulin (RhIG) protects D-negative mothers against production of anti-D.
80
When should a mother receive Rh immune globulin (RhIG) if the baby is Rh+?
If the baby is Rh+, the mother must receive RhIG within 24-72 hours.
81
What is the recommended blood type given to Rh-negative individuals?
Rh-negative individuals should receive Rh-negative blood.
82
When is the initial administration of Rh immune globulin (RhIG) to Rh-negative moms?
RhIG is initially given to Rh-negative mothers at 28 weeks gestation.
83
What do superscripts refer to in genetics?
Superscripts (Rh1) refer to genes inherited from both parents.
84
What do subscripts refer to in genetics?
Subscripts (Rh1) refer to the agglutinogen (complex of antigens) inherited from both parents.
85
How is the Rh1 gene expressed in shorthand notation?
The Rh1 gene codes for the Rh1 agglutinogen made of D, C, and e, which is usually written as DCe (leaving out the 'h').
86
What are the characteristics of Rh antigens?
Rh antigens are proteins of 417 amino acids that cross the red cell membrane 12 times, with only small loops on the exterior.
87
What is the Rosenfield system used for?
The Rosenfield system is used for computer data entry without making genetic assumptions in the Rh system.
88
How are antigens designated in the Rh system?
Antigens are designated by numbers, for example: Rh1 = D, Rh2 = C, Rh3 = E, Rh4 = c, Rh5= e.
89
What does the ISBT organization do?
The ISBT is an international organization that standardizes blood group system nomenclature by assigning 6-digit numbers for each antigen.
90
How are genotypes determined from phenotypes?
Genotypes are determined by statistical probability based on the phenotype and gene frequency in a population.
91
How can the most probable genotype be determined?
Once the phenotype is known, the most probable genotype can be determined based on the most common genotypes.
92
What are the possible genotypes for Rh antigens D, C, c, E, and e?
Possible genotypes include homozygous and heterozygous combinations of the antigens.
93
What should be done if testing results show D+ C+ c- E- e+?
If testing results show D+ C+ c- E- e+, start with D and determine if it's positive or negative.
94
If D is positive, what can be deduced about the individual's genotype?
If D is positive, the individual is either homozygous or heterozygous for D, but it cannot be determined from these results alone.
95
What should be done if C is negative?
If C is negative, put c on each chromosome.
96
How can the homozygosity or heterozygosity of C be determined?
If C is positive and there is no c present, it is homozygous. If both C and c are present, it is heterozygous.
97
What can cause interference with all cells reacting?
Cold agglutinin
98
What is the most common cause of false positive anti-D testing?
Spontaneous agglutination when red cells are DAT positive
99
When should you re-type a patient with low-protein reagents?
If using high-protein reagents and both the patient and the Rh control are positive
100
What may cause false-positive Rh results?
Rouleaux caused by the presence of abnormal proteins in patient serum
101
What should you do to resolve false-positive Rh results caused by rouleaux?
Wash cells in saline and re-test
102
What can lead to false-positive reactions in blood bank testing?
Reagent contamination or bacterial contamination of reagents
103
What can lead to false-positive Rh typing?
Antibody to a low incidence antigen
104
What should you do if there is unidentified antibody to a low incidence antigen?
Test with another manufacturer's reagent
105
What can cause false-negative results in blood bank testing?
Incorrect cell suspension or incorrect cell to serum ratio
106
What can result in the dispersal of weak D agglutination?
Overly vigorous re-suspension after centrifugation
107
What can result in the destruction of antibody in reagents?
Prolonged or incorrect storage of reagents
108
What may not react with weakened forms of an antigen?
Specific antibody that does not bind complement
109
What is the most common class of Rh antibodies?
IgG
110
When do Rh antibodies usually appear after exposure to Rh antigens?
Within 6 weeks to 6 months
111
What type of media is best for demonstrating Rh antibodies?
High protein media or IAT
112
What temperature is best for incubating Rh antibodies?
37°C to mimic in vivo conditions
113
What enhances the reaction of Rh antibodies?
Testing against enzyme-treated RBCs
114
Why do Rh antibodies not bind complement?
Rh antigens are too far apart on the RBC to allow two antibodies to bind close enough together
115
When should anti-serum be added to the test?
Prior to the addition of cells
116
What should be done if label is missing or unreadable on reagents?
Never use the reagents
117
What should be done if wrong anti-serum is used?
Always read label to avoid the problem
118
What is the result of hemolysis in extravascular Rh system antibodies?
The result of hemolysis in extravascular Rh system antibodies is picked off by phagocytic cells of the liver and spleen.
119
How long does detectable antibody usually persist?
Detectable antibody usually persists for many years.
120
What happens when antibody levels fall below detectable limits?
When antibody levels fall below detectable limits, a second exposure to the Rh system antigen will produce a rapid secondary immune response.
121
What is the order of immunogenicity of Rh antibodies?
The order of immunogenicity of Rh antibodies is D > c > E > C > e.
122
When should Rh typing be investigated?
Rh typing should be investigated when the Rh control test is positive or when results are weak or 1+ with commercial anti-D antiserum.
123
What should be done if mixed field agglutination is suspected?
If mixed field agglutination is suspected, microscopic readings should ONLY be done.
124
What should be done if an Rh typing discrepancy is found?
If an Rh typing discrepancy is found, the patient history should be reviewed and previous results must be compared to current results.
125
What type of blood must be administered if a transfusion is required before resolution of an Rh typing problem?
Rh negative blood MUST be administered until the Rh typing problem is resolved.
126
What may be the cause of false positive reactions with anti-D?
False positive reactions with anti-D may be due to the presence of antibodies to antigens of low frequency in the antiserum.
127
What is recommended for all Rh testing?
Rh control is recommended for all Rh testing, especially for an AB individual.
128
When should a DAT be performed as a control?
A DAT should be performed as a control for selected samples, such as cord, neonatal, samples demonstrating autoagglutination, to rule out false negative Rh typing due to blocked antigens.
129
What should be done if there is doubt about the identity or specimen quality?
If there is doubt about the identity or specimen quality, a new specimen should be collected and re-tested.
130
What may have caused a discrepancy if it has been resolved?
If a discrepancy has been resolved, it may have been caused by a procedural error, anti-sera not added, incorrect anti-sera used, a too strong cell suspension, excessive or insufficient centrifugation, tubes shaken too vigorously with weak agglutinates dispersed, or failure to re-suspend the entire cell button from the bottom of the tube.
131
What are some possible causes of mixed field agglutination?
Some possible causes of mixed field agglutination include recent transfusion with different Rh donor units, contaminated specimen, or an unusual Rh phenotype.
132
When is it not necessary to transfuse recipients with Rh Negative blood?
When they type as Rh Negative by direct methodology.
133
What are the different types of Rh ANTISERA?
They may be low protein, high protein, saline based, chemically modified, monoclonal, or blends of monoclonals.
134
Which Rh typing reagent was the first available and cannot be used for weak D testing?
Saline reagents, which contain IgM immunoglobulin.
135
Why can't saline anti-D be used to test cells coated with IgG antibodies?
It is low protein based and cannot be used to test cells coated with IgG antibodies, such as in weak D testing.
136
What can cause FALSE POSITIVE Rh TYPING?
Spontaneous agglutination of DAT positive cells, immunoglobulins on the surface of red cells, presence of cold agglutinin, reagent contamination, presence of unidentified antibody to a low incidence antigen, failure to follow manufacturer's instructions, or adding wrong reagent to test.
137
What can cause FALSE NEGATIVE Rh TYPING?
Red cell suspension too heavy, failure to add antisera, incorrect antisera added, failure to follow manufacturer's instructions, deterioration of anti-D antisera, inappropriate technique, resuspension of cell button done too vigorously, failure of anti-sera to react with variant antigen, or anti-sera in which the antibody is directed against a compound antigen.
138
What are LOW PROTEIN REAGENTS?
They are the most recent Rh reagents introduced, including monoclonal antibodies derived from human/murine sources, suitable for different methods, and contain IgM or IgG monoclonal antibody for Rh control and weak D testing.
139
What are the components of SLIDE AND MODIFIED TUBE ANTI-D?
IgG anti-D in protein concentration of 22-30%, mainly albumin, but other potentiators may be present.
140
Why is Rh control essential for Rh(D) typing tests?
The Rh control is essential because it contains everything present in the anti-D typing sera except the anti-D, ensuring accurate testing.
141
What determines if a genotype is homozygous or heterozygous?
The presence or absence of the same allele on both chromosomes determines if a genotype is homozygous or heterozygous.
142
What is the more common genotype: DCe/dCe or DcE?
DCe/dCe is more common than DcE.
143
What is the genotype if someone has D+, C+, c-, E-, and e+ antigens?
The genotype is D+ C+ c- E- e+.
144
What can phenotyping be used for?
Phenotyping can be used for parentage testing, predicting HDFN, and confirming Rh antibody specificity.
145
What is the protocol for Rh phenotyping?
The unknown RBCs are mixed with Rh antisera, and agglutination indicates the presence of the antigen on the cell, determining the phenotype.
146
Why is molecular testing becoming more popular for blood group genes?
Molecular testing is used when anti-sera is not available for some antigens, and it can differentiate recently transfused individuals.
147
What is Tippett's theory regarding the RHD and RHCE genes?
Tippett's theory states there are two closely-linked genes: RHD determines the presence of the D antigen, and RHCE determines the production of C, c, E, and e antigens.
148
How many Rh genes do D positive people inherit from at least one parent?
D positive people inherit 2 Rh genes from at least one parent.
149
What are the presumptive and most probable genotype frequencies listed as?
The textbook lists the genotype frequencies as 'presumptive' or 'most probable'.
150
What process are paternity testing of blood group Ag's based on?
Paternity testing of blood group Ag's is based on a process of exclusion.
151
How many alleles can be inherited at the LW locus?
Three alleles can be inherited at the LW locus.
152
Which allele is the most common at the LW locus?
LWa is the most common allele at the LW locus.
153
Which allele is much less common at the LW locus?
LWb is much less common at the LW locus.
154
What does the LW allele code for?
The LW allele codes for NO LW antigen.
155
What is the genetic nature of LWa and LWb alleles?
LWa and LWb alleles are co-dominant.
156
What is the genetic nature of the LW allele?
The LW allele is recessive.
157
Where does LW negative occur?
LW negative occurs in all Rh null people.
158
What do the CDE antigens require for LW antigens?
CDE antigens are required for LW antigens.
159
How often is Anti-LW seen in laboratories?
Anti-LW is rarely seen in laboratories.
160
When should the investigation of mosaic D consider anti-LW?
The investigation of mosaic D should consider anti-LW when a D positive patient appears to have formed anti-D.
161
Which blood cells does LW antigen react more strongly with?
LW antigen reacts more strongly with D positive blood cells than with D negative blood cells.
162
What are some causes of positive Rh Control?
Rouleaux when unwashed cells used, Strong autoagglutinins, Positive DAT.
163
What are some causes of negative Rh Control?
Excessive feto-maternal bleed, Dual red cell population due to bone marrow transplant, Genetic anomalies.
164
What are Rh deletion phenotypes and how do they affect antigen expression?
Rh deletion phenotypes occur when pieces of the genetic material representing CE antigen are deleted. They enhance expression of D antigen and lack alleles at the Ee locus or Ee and Cc loci.
165
How are Rhnull individuals characterized?
Rhnull individuals have no Rh antigens (D, C, c, E, e) detectable on their red cells. They can transmit normal Rh antigens to their offspring.
166
What is the common type of Rhnull phenotype?
The common type of Rhnull phenotype has the core Rh polypeptide missing.
167
What is the less common type of Rhnull phenotype?
The less common type of Rhnull phenotype has the regulator gene that turns off the expression of Rh missing.
168
What is the impact of Rhnull phenotype on other blood group antigens?
Rhnull individuals are also negative for antigens like S's, U, and LW due to their absence of Rh antigens.
169
What are the characteristics of Rhmod phenotype?
Rhmod phenotype is similar to Rhnull phenotype, but the Rh antigens are present in greatly reduced amounts due to a mutation of the RHAG gene.
170
What is the immune antibody Anti-Rh29?
Anti-Rh29 is the immune antibody made by rare people of the Rhnull type. It is usually potent and may cause transfusion reactions or hemolytic disease of the newborn.
171
What is the serological significance of LW antigens?
LW antigens are serologically similar to Rh, and they react strongly with D positive cells and weakly with D negative cells.
172
When should RhIG be administered to Rh Negative women?
Within 72 hours of delivering an Rh Positive baby
173
What is the purpose of RhIG?
To prevent the formation of permanent anti-D antibody
174
Why is anti-D injected passively?
To bind to any Rh Pos cells from the fetus
175
How is weak D expression identified?
Through weakly expressed D antigen after incubation and antiglobulin testing
176
What are the three ways weak D occurs?
Positional, Mosaic, Genetic
177
What is the weak D Du phenotype?
Weakly expressed D antigen seen as agglutination that easily breaks apart
178
Which population is weak D more common in?
Blacks
179
Can weak D testing be performed using Gel methodology?
No
180
When should RhIG be administered to Rh Negative women?
Within 72 hours of delivering an Rh Positive baby
181
Which genetic variation causes weak D?
Quantitative variation of D gene
182
What antigens are usually found together with anti-C?
C, e, E
183
Which Rh antigen is found on cells carrying the D antigen?
G
184
What are the low incidence Rh antigens?
Cw, V, VS, Rh32, Rh33
185
What type of antibodies are usually made by exposure to Rh antigens?
IgG
186
How are Rh antibodies detected?
Through the IAT (Indirect Antiglobulin Test)
187
What is the importance of checking patient history for Rh antibodies?
To determine if a rapid secondary response may occur upon re-exposure to the antigen
188
How can false positive results be enhanced in Rh antibody testing?
High protein, low ionic strength solution, enzymes, or polyethylene glycol
189
What can antibodies to the Rh system cause?
Hemolytic transfusion reactions
190
What should be done if the Rh control is positive?
Perform a DAT (Direct Antiglobulin Test) to determine if uptake of alloantibody or autoantibody is causing the positive Rh Control
191
What should be done if the Rh cannot be determined and transfusion is required?
Transfuse Rh Negative blood
