RH and LW blood groups

What is the difference between Rh positive and Rh negative individuals?

Rh positive individual have the D antigen, Rh negative individuals have no D antigen

What disease was Anti-D first described with?

Hemolytic disease of the newborn

Are human anti D and LW the same?

No

What percentage of the population is D/D,D/d positive and what precent are d/d?

• Rh positive: 85%

• Rh negative: 15%

What chromosome is the Rh gene?

Chromosome 1, autosomal dominant

What cells are the D antigen present on?

Only on RBCs, is an integral part of the rbc membrane

What is the clinical significance of D?

It is the second most significant antigen, very high immunogenicity

How many Rh antigens are there?

Approximately 50

What are the five most seen Rh antigens?

• D

• C

• c

• E

• e

What are the three theories of Rh gene inheritance?

• Wiener

• Fisher-Race

• Tippet

What is the Wiener theory of Rh inheritance?

• single locus with multiple alleles

• nomenclature difficult

What is the fisher-race theory of Rh inheritance?

• 3 closely linked loci inherited as a unit

• 1 gene and 1 product per allele

• letter designations

• most used nomenclature system

What is the Tippet theory of Rh inheritance?

• 2 closely linked loci

• used primarily in research

What are the 5 typing reagents for Rh group phenotyping?

• anti D

• anti C

• anti c

• anti E

• anti e

What is dosage?

The amount of antigen present on a homozygous versus the amount present on a heterozygous cell

What can the phenotyping results of Rh typing provide?

An estimate of the genotype

What genotype results in a stronger expression of D?

DcE (R2 cells), reacts more strongly with anti D reagent

What is the cis effect in antigen strength?

• “labilization of ligands that are cis to other ligands”

• Ex. cDE: the E antigen is weaker than in an individual that is cdE

What is the trans effect on antigen strength?

• on different sides

Ex. C and E antigens are weaker in individuals that are CDe/cDE than in individuals that are Cde/cde or cDE/cde

What are some possible causes of weak D antigen expression?

• transmissible gene inheritance

• position effect

• partial D, D mosaic, D variant

What happens in weak expression of D due to transmissible gene inheritance?

• D antigen is weakly reactive

• there are less D antigen sites

What is the notation for weak D?

Du

What is the position effect that leads to weak d expression?

C gene in the trans position to D resulting in weaker D antigen expression

What is the cause of weak D expression in the case of partial D, D mosaic, D varients?

Lack part of the D antigen

Why should weak D be tested for in blood donors?

Though weak D is less immunogenic, weak D+ cells are destroyed by anti D

Is weak D testing done for blood recipients?

Not necessary, as recipients that type as D negative but are actually weak d+ are not harmed by receiving D negative blood

What is the rhi antigen?

• Formed by the Ce (rhi) part of CDe genes in those with the cis position of those gene.

• Not found on those with CDE/cde

What is the f antigen?

• ce (f) as in c and e on the same haplotype

• cDE/CDe individuals do no have the f antigen

What is the G antigen?

• present on most D positive and all C pos cells

• D and C

What is anti-G?

A combo antibody to C and D

• cannot be separated

What does a D negative person make?

Both anti D and C. Can make anti G as well

What happens in gene deletions of Rh groups?

• lack activity at Cc and/or Ee sites

• Cells may show very strong D activity

What are LW antigens?

• present on most human rbcs

• D neg cells have weaker LW activity

• Anti LW reacts with D pos cells and weakly with D neg cells

What is the Rh null type?

No Rh antigens, regulator gene absent, homozygous for amorph gene. Results in rbc membrane abnormalities

What can Rh null individuals be transfused with?

Only Rh null blood