Neonate mixed field reaction

[YorkshireExile]

Just had this recent case in our place.

3.5 month old baby. Mother B Pos. When baby born, had mixed field reaction (using Biorad/Diamed gel cards) with anti-B, strong 4+ reaction with anti-A. DAT negative. Resulted group as undetermined but assumed it might be due to maternal B cells through a fetomaternal haemorrhage. Asked for new specimen after one week to check but one never came.

 

Baby just come back into our hospital at 3.5 months old. Grouping card is showing strong agglutination with anti-A at 4+, as before. But the agglutination is showing very slight mixed field still with the anti-B (maybe 95% to 5% at a guess). The baby was transfused elsewhere with group O blood, last transfused about eleven weeks ago. Also had group A platelets transfused, last time also about ten weeks ago.

 

So the question is, what is causing the slight mixed field with the anti-B? Can`t be the group O transfused cells, or the anti-A would have a mixed field as well. Surely it can`t be from the maternal B cells after all this time? Is it safe to call the baby group AB now?

 

Any suggestions?

 

Thanks.

[Malcolm Needs ☆]

Hi BoroCliff,

What you have to remember is that the A and B antigens are NOT the direct gene products. The direct gene products are, respectively, alpha-1-3-N acetyl-D-galactosaminyl transferase ("A" transferase) and alpha-1-3-N-galactosyl transferase ("B" transferase); in other words, a couple of transferase enzymes.

At birth, these enzymes are not working at their full kinetic capacity, but they are also competing against one another for the Type 2 backbone molecules.

It is quite normal for newborn babies to have weaker A and/or B antigens than do adults.

In this case, mixed-field reactions with the anti-B is almost certainly due to the fact that the "A" transferase was "beating" the "B" transferase in this competition (particularly as it was a newborn - this can also happen, more rarely, in adults).

Although the baby has been transfused with group O red cells, the slight mixed-field reaction in the anti-B means that, although the "B" transferase is "catching up" with the "A" transferase in the "competition", it hasn't quite got there yet!

I think that you would be quite safe in calling this baby group AB.

[YorkshireExile]

Thank you for your excellent answer Malcolm.

 

So this "competition" can still be going on even if the baby is almost four months old?

[Malcolm Needs ☆]

Oh yes. In fact, it goes on, to some extent, throughout life.

[rravkin@aol.com]

Hi BoroCliff,

What you have to remember is that the A and B antigens are NOT the direct gene products. The direct gene products are, respectively, alpha-1-3-N acetyl-D-galactosaminyl transferase ("A" transferase) and alpha-1-3-N-galactosyl transferase ("B" transferase); in other words, a couple of transferase enzymes.

At birth, these enzymes are not working at their full kinetic capacity, but they are also competing against one another for the Type 2 backbone molecules.

It is quite normal for newborn babies to have weaker A and/or B antigens than do adults.

In this case, mixed-field reactions with the anti-B is almost certainly due to the fact that the "A" transferase was "beating" the "B" transferase in this competition (particularly as it was a newborn - this can also happen, more rarely, in adults).

Although the baby has been transfused with group O red cells, the slight mixed-field reaction in the anti-B means that, although the "B" transferase is "catching up" with the "A" transferase in the "competition", it hasn't quite got there yet!

I think that you would be quite safe in calling this baby group AB.

Malcolm,

It is gemes of information like this that keep me so fasinated and interested in BB. But I have to ask, outside of collecting a second specimen later on, do you have any recommendations on reaction enhancement?

Thank you,

Ronald

[Malcolm Needs ☆]

Well, it may be enhanced by lowering the incubation temperature, because the red cells probably don't totally lack (in this case) the B antigen, but have substantially less of the D-galactose being expressed.

[Yanxia]

In our normal blood type, we often see newborn with 4+A antigens and 3+mf B antigens.

[aafrin]

Well, it may be enhanced by lowering the incubation temperature, because the red cells probably don't totally lack (in this case) the B antigen, but have substantially less of the D-galactose being expressed.

 

[aafrin]

I seem to be having problem with reply posting, sorry.

Malcolm, can you explain this further?

I am lost, we have always used lower temperature for enhancing the reverse group reactions of anti-A & anti-B, but never in forward grouping.

[Malcolm Needs ☆]

As long as you use appropriate negative controls (like a group O cell) there is no reason why a forward group should not be performed at temperatures lower than "room temperature" (about 20oC or around there).