Rh Blood group System

Chapter 7- Immunohematology

When are Rh antibodies produced?

ONLY AFTER EXPOSURE to foregin RBC antigens. ( likely through pregnancy or transfusion. Rh are not naturally occurring

antibodies that are against Rh antigens can cause what?

HTR and HDFN

ABO and Hh antigens reside on carbohydrates, whereas Rh antibodies reside on ____

proteins

Are Rh antigens found in secretions or on the RBC membrane?

ONLY FOUND WITHIN THE RBC MEMBRANE

There is no codominace with the D antigen, either you have it or you don’t

;D

Levine and Stentson

-found antibody responsible for HDFN anfd HTR

• mother delivered a stillborn and required transfusions with donated blood from her husband. they found she formed an antibody that reacted with her husbands cells, an antibody that must have been introduced to her by something in the baby

Landsteiner and Wiener

• found Ab in guide pigs and rabbits after transfusing them with rhesus monkey RBC

what are the 5 genes of concern in Rh system

D, C, c, E, e

__% of the population is D pos

85

Rh antigens are well developed at birth, meaning they can cause…

HDFN

What Rh antigen is very frequent, and if you do not have it it is very hard to find compatible blood for you if you lack the antigen?

little e

less than ___ mL of Rh pos RBC can stimulate Ab production in someone who lacks D antigen

0.1 ( D is VERY immunogenicity!)

Most to least likely to illicit an immune response

D,c,E,C,e

It is not uncommon to see several Rh antibodies in a patient (Rh antigens are inhertied very close to another!) For example, anti-D and ____. also, anti-c and ____

anti-D and anti-C

anti-c and anti-E

haplotype

combination of genes inherited from one parent. ex) if one parent has genes D, C, e → DCe is haplotype

genotype

two haplotypes, written as DCe/DcE

Fisher-Race theory of Rh inheritance

three seperate genes, all close in loci (linked) each gene coded for a pair of alleles

Wiener theory of Rh system inheritance

single gene produced Rh antigens

because of a gene deletion or mutation, a person could have no C/c or E/e at all, we’d consider this pateint to be____

Rh null

Rosenthal: 12345

DCEce

1,-2,3,4,-5

DcE

1,2,-3,4,5

R1/r →DCe/dce

How is ISBT nomenclature beneficial?

universal becuase it all is numbers, we get a lot of blood from overseas

When we type for Rh, did we define the phenotype or the genotype?

phenotype

What is the most common genotype for caucasians?

R1r (DCe/dce)

what is the product of Rh genes?

nonglycosylated ( no usgar added) proteins

How many times do the Rh proteins transverse the cell membrane?

12

What is the actual genetic inheriance of Rh genes?

there are 2 genes closely linked on chromosome 1

• RDH gene produces D protein

• RHCE gene produces Ce, cE, CE, ce proteins

Rh proteins can’t become antigens on their own,___ must be present for Rh antigens to be expressed properly

RHAG ( Rh- associated glycoprotein)

What is the role of RHAG

it is a co-expressor allows Rh antigens to be stably expressed on the RBC

What happens if a person has no RHAG?

they are Rh null ( even if RDH and RHCE genes are present) and RBC membrances will become fragile and abnormal

Rh antigens are nonglycosylated proetins that are integral the the RBC membrane, they loop in and out of the membrane, leaving small looks of Rh protein exposed above the surface.

;0

Compared to a normal D positive RBC that has 15,000-33,000 RBCs, weak D has _____

70-52000 sites per cell

what is the position effect?

when one gene interatcts with another gene to modify and weaken the D antigen

The presence of what Gene can cause the position effect and lower the strength/ prevelence of the D antigen?

big C( when big C is trans to D gene)

How does the presence of C antigen interfere with the D antigen?

C antigen structure/ steric arrangement in relation to the D antigen interferes witrh trhe expression of D

Which would cause a weak D antigen expression? Dce/dCe or DCe/dce

Dce/dCe ( this is the trans position, oposite sides… not on the same chromosome. if DC are on the same chromosome that leads to no weak D)

What is the phenotype calls in individuals that posess an extreamly lwo amount of D cells that reagnet anti-D are unable to detect?

D_el

What is one of the only ways we can detect a D_el phenotype?

adsorbing and eluting anti-d of the patients RBC( is neg as IS and Du test)

Patrial D (D mosaic)

D antigen is missing one or more epitopes due to amino acid changes… does not code for the total D antigen

In partial D, is the number of D antigen decreased?

No, there no change in the amount, but there is a change in the quality

In partial D, how will tesing initially look?

they will apear D pos, but can form anti-D if they were given D pos blood

When do you do weak D testing?

Any D neg RBCs

Why could a positive DAT cause a false positive Rh typing?

no D antigen, but a positive DAT supplies RBC bound antibodies that at AHG, could cause the reaction to look positive, when in fact no anti-D antibody even binded to a D antigen, if it was even there

Why could a positive DAT cause a false positive Rh typing?

RBCs are coated with antibody, that blocks another antibody from reacting with D antigen. D antigen is blocked by the other antibodies.

Do Rh antibodies drop below detectable levels?

no

When can we detect Rh antibodies?

at 37C or at AHG ( warm reacting IgG)

what is the order of frequency for Rh antibodies?

Anti-D, Anti-E, Anti-c, Anti-C, Anti-e

What are some signs someone is having a reaction to transfusion?

fever, mild bilirubin elevation, decrease in hemoglobin and haptoglobin

why would we see a decrease in haptoglobin in a transfusion rxn?

Haptoglobin binds to free hemoglobin in the blood, if donor cells are lysing, that would release hemoglobin in the blood.

HDFN

mom’s Ab crosses placenta and attacks baby

liklihood of an Rh mother carrying a fetus that is Rh positive is very high.

;0

how can we prevent D-neg mothers from forming anti-D?

purified anti-D if given to mother before and after delivery of D pos baby.

how does rhogam work?

Pasiive IgG anti-D are in mom, so if she is exposed to D pos cells, the passive IgG with remove the D pos blood before the immune system can even see it can cause a respone. no memory cells are made, and no antibodies are made that sticka round