So we've have an elderly lady's sample sent to our reference lab with ?Anti-D but when tested against 2 of our panels it's 3+ in the IAT cells and negative in Enzyme IAT.

It was my understanding that the D antigen was entirely resistant to papain treatment. Are some epitopes cleaved off during the process which could be causing these reactions?

I should also add that she is D negative!

Any off chance (even though elderly), she got RhIg, or IV Immunoglobulin?

I can't recall having come across an anti-D reacting like this (as far as I can remember these days - which isn't very far at my age!!!!!), but I do remember once finding an anti-E that only reacted by IAT, and not with enzyme-treated red cells, which I sent to the International Blood Group Reference Laboratory for confirmation, and it was confirmed by no less a person than Joyce Poole. We published a poster about it at a BBTS Annual Scientific Meeting (MacRate EB, Carrington T, De Lord C, Needs M, Win N.  Anti-E Detectable by IAG and Not by Enzyme?  How Confusing!  Transfusion Medicine 2001; 11 (Suppl. 1): 30.).

It is my understanding that, while resistant, it is not totally unaffected and can even be enhanced due to cleavage.

From the internet search:

• Rh Antigens and Papain: While intact Rh-positive red blood cells treated with papain may not show a change in the size of the Rh-containing polypeptides, sequential treatment with phospholipase A2 followed by papain does result in cleavage of a 35-Kd protein band to a 30-Kd band, suggesting some effect on the Rh-related polypeptides.

• Increased Agglutination: Interestingly, papain treatment often leads to enhanced agglutination (clumping) of red blood cells by anti-D antibodies. This suggests that while the D antigen itself might not be entirely destroyed, the changes in the red cell membrane caused by papain somehow make the antigen more accessible to the antibody or enhance the agglutination process. One theory is that papain modifies the red cell surface, reducing its electronegativity and exposing hidden antigens. 

Here's a couple of articles discussing:

https://www.sciencedirect.com/science/article/pii/S0006497120626842

https://www.sciencedirect.com/science/article/pii/S0006497120858455#:~:text=studies%20described%20here.-,RESULTS,produce%20other%20detectable%20cleavage%20products.

Very interesting ... thank you!

5 hours ago, Cliff said:

Any off chance (even though elderly), she got RhIg, or IV Immunoglobulin?

Not that we can tell, just an untransfused pre op patient.

5 hours ago, Malcolm Needs said:

I can't recall having come across an anti-D reacting like this (as far as I can remember these days - which isn't very far at my age!!!!!), but I do remember once finding an anti-E that only reacted by IAT, and not with enzyme-treated red cells, which I sent to the International Blood Group Reference Laboratory for confirmation, and it was confirmed by no less a person than Joyce Poole. We published a poster about it at a BBTS Annual Scientific Meeting (MacRate EB, Carrington T, De Lord C, Needs M, Win N.  Anti-E Detectable by IAG and Not by Enzyme?  How Confusing!  Transfusion Medicine 2001; 11 (Suppl. 1): 30.).

That sounds interesting and very similar!

We're thinking to run the Bio-Rad variant D kit as it may just be a variant and just showing as D- in the cards which happens occasionally. Still a bit strange for any kind of anti-D to show reactions like this.

I'll do the same as you did and have a chat with IBGRL about our findings to see if it's of any interest to them.

52 minutes ago, Pan-reactive said:

I'll do the same as you did and have a chat with IBGRL about our findings to see if it's of any interest to them.

Thanks for that. I would thoroughly recommend what you are doing. Try contacting Nicole Thornton - she is ABSOLUTELY BRILLIANT!!!!!!!!!