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Hi,

We recently encountered a pregnant mother with known history of anti-Jra. We have worked on her samples on two separate occasions and was able to rule out the presence of other common alloantibodies using the alloadsorbed plasma. Just three week ago, we worked on the her sample and this time the alloadsorption failed to remove anti-Jra. The reaction strengths of the adsorbed plasma were no difference compared to neat plasma when tested with the panel cells. DAT is negative. Patient's neat plasma was non reactive with all Jra- cells.  ? additional antibodies to enzyme sensitive antigens?

I am thinking the next time, I probably should perform elution to see if the anti-Jra get adsorded. Low affinity anti-Jra??

Any thoughts?

Emergency room

 

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There has only been one example of anti-Jra causing HDFN in the literature, and NO examples of "enzyme-only" antibodies causing HDFN.

As you know that the antibody is an allo-antibody, why would you want to do an eluate?

To find an anti-Jra is both rare and exciting, but I really would caution about going "overboard" about testing.

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I wanted to perform an elute on the adsorbed cells to see if the anti-Jra gets adsorbed out or there maybe additional alloantibodies.  We have worked a couple of anti-Jra cases and most can be adsorbed out in order to rule out any other antibodies to common antigens in the adsorbed plasma.

 

Emergency room

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Yes, but if you are adsorbing out the anti-Jra by alloadsorption (which is EXACTLY the right think to do during a pregnancy), if you perform an elution on the adsorption cells, about the only thing that you are going to detect in the eluate is the anti-Jra, unless you test the eluate against Jr(a-) red cells, which you could do with raw plasma/serum, could you not?

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The issue here is the alloadsorbed plasma (2X) reactivity is still positive and same reactivity strength compared to the neat plasma ? low affinity of anti-Jra ? but why the last couple times we were able to adsorbed out the anti-Jra. Can the patient make another highs to antigens sensitive to enzyme (the adsorbed cells are phenotypically similar cells papain treated)?

I am going to try perform the eluate and test it against Jra- cells.

 

 

 

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Anti Jra is quite common in Korea and they sometimes send some samples to our reference lab in Switzerland for testing.  The reference lab have previously reported difficulty in adsorbing  out allo-anti-Jra too

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1 hour ago, galvania said:

Anti Jra is quite common in Korea and they sometimes send some samples to our reference lab in Switzerland for testing.  The reference lab have previously reported difficulty in adsorbing  out allo-anti-Jra too

Yes, I am not saying that anti-Jra isn't difficult to adsorb out; it certainly can be.  What I am questioning is the value of making an elution from the cells that are used to adsorb out the anti-Jra (albeit unsuccessfully), as you would detect the anti-Jra (obviously) on the red cells, and so would still have the problem that it would be highly unlikely that any other specificity or specificities would be detected, unless using Jr(a-) red cells - which could be done with the neat plasma.

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What if the anti-Jra is not actually getting onto the adsorbing cells?  Could that be emergency room's point?  If the eluate does not contain anti-Jra then it would prove that is why the adsorption isn't working.  But I would think even a little bit of antibody that adsorbed (even if it is not enough to affect the strength of the reaction of the adsorbed plasma) could make the eluate contain anti-Jra so the odds of the eluate lacking it would be astronomically small.

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On 8/28/2018 at 2:58 AM, emergency room said:

? low affinity of anti-Jra 

Hi, with my limited knowledge, am I right to assume that the affinity of this antibody should be the same as the previous 2 times that you have tested the patient samples? If affinity doesn't change, and if the methods are consistent, could it be that the pregnant lady's anti-Jra is being 'boosted' by fetal Jra (considering it is a HFA)? Or maybe there is a 'steric-hindrance' sort of thing that is preventing proper adsorption? Thanks

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Hi Muhammad,

I would hesitate to say that the affinity of an antibody will not change.  It is well documented that this is just not so.  For example, a de novo polyclonal anti-D will mimic an anti-I and/or anti-i, however, a fully developed anti-D will react "only" as an anti-D (see, for example, Sompayrac L.  How The Immune System Works. 5th edition, 2016, Wiley Blackwell, where he explains immune adaptation).  At the same time, it is almost certain that the pregnant woman's anti-Jra is being "boosted" by almost silent foeto-maternal episodes of haemorrhage, as has been shown to occur often in cases of maternal anti-D, when the pregnant woman is carrying a D Positive foetus (hence, the National Institute for Clinical Excellence [NICE UK], sanctioned routine antenatal anti-D prophylaxis [RAADP]), and, as you suggest, as the Jra antigen is a high prevalence antigen, it is unlikely (although not impossible) that the foetus would also be Jr(a-).

As the carrier molecule has three external loops (external to the red cell membrane), it would seem unlikely that there is steric hindrance preventing adsorption, and, certainly, in the three cases of anti-Jra that I have been involved with, we had absolutely no problem adsorbing out the antibody.

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