hi there,

was wondering if someone could tell me if it is possible for someones phenotype to be negative for C and c. but for them to express the D and E antigens. and if so would this person be used as a bone marrow donor. Have just recently sat the higher specialist exams in blood transfusion and one of the case studies involved selecting the appropriate blood for the BM recipient post transplant.

confused

thanks:confused:

hi there,

was wondering if someone could tell me if it is possible for someones phenotype to be negative for C and c. but for them to express the D and E antigens. and if so would this person be used as a bone marrow donor. Have just recently sat the higher specialist exams in blood transfusion and one of the case studies involved selecting the appropriate blood for the BM recipient post transplant.

confused

thanks:confused:

As far as I know, such a phenotype has not been described.

Certainly there are -D-, CD- and cD- haplotypes have been described, sometimes in the homozygous state (in fact, normally in the homozygous state), but these are exceptionally rare.

I know of no reason why such individuals could be used as bone marrow donors, but their Rh type would be far, far less important than their HLA type in such a situation.

Post-BMT, such donors would not be used, unless in very exceptional circumstanes, as there would be very little need for such blood, and in any case, they would be so rare that the world's frozen blood banks would soon run out of such blood.

I think that the question probably referred to what ABO and what D type blood would be used in the case of either a minor or major mis-match.

If you look in the library section at the top of the page, under UK Guidelines and find the one about compatibility testing, you will see what we do in the UK.

:):)

Edited September 17, 201014 yr by Malcolm Needs
Forgot a bit.

thanks malcolm,

In the case study it gave you the donors phenotype which was both C and c negative and I was wondering whether or not that this was a mis-print in the paper. I have read about RH null individuals but had never come across someone who was just negative for C and c antigens.

thanks again

Sounds like a mis-print to me, but then you do get some very strange questions in some written papers, simply because the person writing it changes things to fit what they want to ask, without recourse to what is likely and what is not (and, sadly, sometimes without recourse to any knowledge on the subject themselves).

Would there is a likelihood of testing the knowledge of donor against recipient's antigen which donor is defected? Like this case the have not C and c antigen, but lots of recipient will have it, so this will be immune against the C and c antigen, and about the post-transplant transfusion, it is a difficulty, too.

It is sure the author just to fit their want, as Malcolm said.

I've attached a cartoon I've drawn which may explain why you do not get C-, c-, red cells that are E+ and/or e+.

You will see from this that the amino acid residues that control the expression of the C/c antigen are all to the left of the amino acid residues that control the expression of the E/e antigen. This means that the codons encoding the amino acid production for C/c are in an earlier exon(s) than that encoding the amino acid production for E/e.

However, you will also see that there are 4 different locations at which the amino acid residues "control" the expression of C/c. If one of these amino acids is substituted with another, you may still get some sort of C or c antigenicity (but almost certainly a partial/variant C or c), but if more than one is substituted, you will either get a nonsense codon, or a codon that is a stop codon, and the resultant protein will not be embedded in the red cell membrane properly, and you will not then express the E/e antigen either.

On the other hand, if there is an amino acid substitution at 226, that does not cause a stop codon, but does produce a nonsense codon, then the resultant protein may be inserted into the red cell membrane (with normal expression of the C/c antigen, but with no expression of the E/e antigen.

I hope that helps!

:D:D:D:D

Rh CE polypeptide.pptx

This post is wonderful, Malcolm. Thank you very much!

My pleasure.

hi malcolm just wanted to say thanks for that excellent explanation and thankyou for taking the time to do it. It was really helpful!

So glad I found this website and all the help and advice I have received has been great!

tricia:D

Hi Tricia

Hope the exam went well after all the studying you put in! Let us know how you get on (if you don't mind of course!).

How did you find the exam?

Best wishes for the results...

Fluffy

hi fluffy,

Am really not sure how I got on - I didnt run screaming from the exam hall when I looked at any of the papers so I am hoping that is a positive!. It was a really good learning experience to go and sit the exams and even if I am unsuccessful this year I will definitely do them again next year. I feel that there is so much to learn and that I have gained alot of knowledge which I will hopefully continue to build on.

Only 3 of us sat the Transfusion exam this year!!

This site has been an invaluable resource of information and advice and i enjoy reading all the interesting posts.

kind regards

Tricia

Sounds like you were in the right frame of mind & very well-prepared. Fingers crossed for you!

I agree I think this site is excellent & vey friendly too.