Rh Blood Group System

Question 1

Rh blood group system general

Answer 1

2nd most important blood group system after ABO
5 principle antigens:
D, C, E, c, e

Question 2

Rh gene organization

Answer 2

RhD & RhCE are 2 different genes on Chr. 1
transcribed in opposite directions -toward each other
RhD & RhCE arose recently from the duplication of one Rh gene

Question 3

Rh protein function

Answer 3

traverses the membrane 12x; exact function is unknown- clearly a transport molecule
likely a CO2 transporter
necessary for membrane integrity!! People w/ Rhnull phenotypes have a hemolytic anemia

Question 4

Rh system antigens

Answer 4

RHD: D antigen (37 epitopes) & G antigen
RHCE: C/c, E/e, G antigen, f ( compound of c&e epitopes), and Cw antigen

Question 5

Rh antigen characteristics ( general)

Answer 5

protein antigen only
expressed ONLY on RBCs
present on RBCs at birth
autosomal codominant expression

Question 6

D antigen statistics:

Answer 6

europe:
RhD pos 85%
RhD neg 15%

Question 7

RhCE antigen Cw

Answer 7

mutation from glutamine at position 41 to arginine
can be involved in serious HDFN & mild transfusions reactions
found in 2% of whites; rare in black populations

Question 8

G antigen

Answer 8

any person w/ D or C antigen has the G antigen
a patient w/ an anti-G antibody would look like they have two antibodies (antiD & antiC)
patients will receive RBC that are Rh D & C neg

Question 9

Fisher-Race antigen terminology

Answer 9

D, C,c, E, e

Question 10

Weiner Antigen terminology

Answer 10

RhD & RhCE are linked & inherited as a haplotype
Rh pos:
R0-cDe
R1-CDe
R2-cDE
Rz-CDE
Rh neg:
r-cde
r'-Cde
r''-cdE
ry-CdE

Question 11

R0

Answer 11

cDe

Question 12

R1

Answer 12

CDe

Question 13

R2

Answer 13

cDE

Question 14

Rz

Answer 14

CDE

Question 15

r

Answer 15

cde

Question 16

r’

Answer 16

Cde

Question 17

r’’

Answer 17

cdE

Question 18

ry

Answer 18

CdE

Question 19

3 most common genotypes overall

Answer 19

R0 (cDe), R1 (CDe), r(cde)

Question 20

most common genotype in white population

Answer 20

R1-CDe

Question 21

most common genotype in the black population

Answer 21

R0- cDe

Question 22

most common RhD negative genotype

Answer 22

r- cde

Question 23

causes of Weak D expression

Answer 23

genetic- most often
position effect
partial D

Question 24

Genetic Weak D

Answer 24

due to inherited weak expression of D antigen
occurs when one has one chromosome that does not code for D antigen & one intact allele that has mutated such that the protein is unstable
requires IAT to detect weak D

Question 25

Weak D: position effect

Answer 25

D antigen is in ‘trans’ location to C antigen: cDe/CDe

detected at immediate spin w/ new antiD reagents

Question 26

Weak D: partial D or D mosaic

Answer 26

one chromosome lacking D; one with part of D

possible for a person to be Rh pos & have an antiD antibody that are made against the missing epitopes

Question 27

When to test for weak D

Answer 27

in RhD neg donors:
if positive for weak D the unit of donated blood is labeled as RhD positive
RhD neg infants: if child is weak D then mother should be treated again w/ anti-Rh

Question 28

Lab detection of weak D

Answer 28

weak D uses IgG antiD
incubation, washing, addition of AHG
important to run an Rh control

Question 29

Rh null phenotype

Answer 29

no detectable Rh antigens
absence of Rh antigens = mild hemolytic anemia
only receive blood from other Rh null people

Question 30

Clinical significance of Rh system

Answer 30

IgG class - cross placenta & cause HDNB

Question 31

antigenicity of Rh antigens

Answer 31

D>c>E>C>e