Weakened P1 expression in pregnancy

[Alisun]

Hello all,

I work in a reference laboratory in the UK.  We referred a sample for further investigation to another reference laboratory.  The report that we had back found the following

Anti-P1 microscopically by 18C direct agglutination with cells that have strong P1 expression.  No reactivity in LISS IAT with untreated or papainised cells.  The patient's cells were found to react extremely weakly with two examples of anti-P1, compared to much stronger reactions with known P1+weak control cells. This finding is likely due to suppression of the patient's P1 antigen, which is not uncommon in pregnancy.

I was not aware of suppression of P1 in pregnancy and could not find any references in Blood Group Antigen Facts Book or Geoff Daniels Human Blood Groups.  Could anyone shed any light on the mechanism and some helpful references?

 

Kind regards

Alison 

[Malcolm Needs ☆]

I have never heard of this either.

I do just wonder, however, if the person who wrote the report was slightly confused with the findings of one of my old colleagues, Dr Elizabeth (Jan) Ikin (or, EWI, as she was often called) and her coworkers, who found that, where the foetus was positive for the P1 antigen, the P1 antigen is expressed quite strongly on early foetal red cells (12 weeks of gestation), and that the expression weakens throughout the pregnancy, and only reaches adult strength of expression by seven years or more.  The reference for Jan's paper is:

Ikin EW, Kay HEM, Playfair JHL, Mourant AE.  P₁ antigen in the human foetus.  Nature 1961; 192: 883.  

doi:10.1038/192883a0

[Alisun]

Thanks for the quick reply.  Good to know that I am not the only one who had not heard of this. 

[exlimey]

That's a new one for me too.

Microscopically detectable auto-anti-P1??? I think someone had a little too much coffee.