Blood Bank Lecture 3 - Rh Blood Groups

ABO Rh Blood Group

There are no naturally occuring antibodies.

D Antigen (2)

• Most routinely tested

• Most immunogenic

C, E, c, and e antigens

Dealt with a correspondding antibody is detected and identified in the patient’s serum

Complex System

49 Antigens

What two genes are found on Chromosome 1

RHD

RHCE

RHD

Coding for the PRESENCE / ABSENCE of the D Protein

RHCE

Codes for the PRESENCE of the other proteins = C,c, E, e

RHAG (2)

• Located on Chromosome 6 which is a co-expressor gene

• MUST BE PRESENT for successful expression of the Rh antigens

Immunogenecity

D > c > E > C > e

Nomenclatures for Rh Blood Groups

Fisher-Race

Wiener

Rosenfield

ISBT

Fisher Race

• 3 separate but close linked genes

• Antibody from exposure to antigen NOT PRESENT in the patient

• Developed antibodies recognize a single antigen

Wiener

• Multiple alleles at one complex locus

• One locus can encode for production of AGGLUTINOGEN which has 3 factors

• Antibodies can recognize single or multiple factors

Rosenfield (4)

• no genetic assumptions

• Numerical system = Rh1 - D antigen

• Number w/ - sign = Antigen isn’t present

• No listing whatsoever = antigen NOT DETERMINED

ISBT (3)

• Six digit number for each antigen specifically

• FIRST 3 DIGITS - indicate the blood group system

• LAST 3 digits - indicate the blood group antigen specifically = 04001 = D antigen of the Rh system 001001 = A antigen of the ABO system

Rh Antigens (3)

• Assist with integrity and intracellular cation transport

• Lack of some Rh antigens = DELETION for missing antigen

• Lack of ALL RH SYSTEM ANTIGENS = Rh Null

E.g. = BOMBAY

If Mom is Dce/DcE and father is dce / dcE, what is one possibility

DCe/dce

Rh Phenotyping Use (5)

• Parental / paternity testing

• Predicting HDFN

• Confirmation of RH Antibody specificity

• Finding compatible blood for transfusion recipients w/ Rh antibodies

• Determine possible genotypes and avaibility of antigen negative blood

Weak Rho(D) (2)

• Requires more initial testing

• Demonstrates hemagglutination onto the 37c incubation phase AFTER the AHG testing phase

Weak D MECHANISMS

• Quantitative / Genetic

• Position Effect

• Partial / Mosiac D antigen

Quantiative D (3)

• RHD gene codes for weak expression of D

• When D antigen is complete, there are fewer D antigen sites on the RBC

• As a result, there are only 70 to 5,2000 D sites on a cell.

Weak D - Position Effect

• Antiglobulin test that demonstrates IgG antibody on the red cell = if Rh control is pos = cells have IgG BEFORE TESTING.

D Mosiac / Partial D

Patient transfused D pos red cells = CHANCE of anti-D alloantibody that becomes part of the epitope that is MISSING.

C in the Trans Position to D

C creating a LIMITING effect on the expression of D resulting in a weak D expression

Deletions of Cc and / or Ee (D— / D..)

Represent partial locus deletions

Exalted D - unusually strong D antigen expression

• Commonly seen in marriage between relatives

Cis-Product antigens (4)

RH6 - cis ce / f = c& e inherited as haplotype (cde / cDe)

Rh7 - cis Cee / rhi = C & e inherited as haplotype

Rh27 - cis cE

Rh22 - cis CE

Cw (4)

• NO ALLELES for C & c

• C & Cw usually tg.

• 2% of caucasians = VERY RARE in afro-amer

  • Anti-Cw can be nat occur + show dosage

f (ce) (3)

When c & e are in cis position = dce / Dce haplotype

COMPOUND antigen

Anti-f antisera can be helpful for phenotyping

Ce ( 3)

When C & e are in cis position

COMPOUND antigen

Antibody helpful for phenotyping

G (3)

• Antigen always found with D (-) and C - POSITIVE RBCs

• Anti-G appears to bind with D, C, G antigens but can look like anti-C + Anti=D are present / CANNOT BE SEPARATED.

• Anti-G commonly found in Rh negative pt. who was only exposed to C antigen

Deleted Rh phenotypes

• Occurs from replacement of large portions