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Antibody stimulation by antigen negative blood?

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We recently had an antenatal case which showed some unusual features.

This was the third pregnancy, the first miscarried at less than 10 weeks. The second was delivered after a seemingly uneventful pregnancy.

At booking we found enzyme anti-f. At 28 weeks anti-f, anti-K and a further unidentified Ab. (f and K enzyme only).

By 32 weeks She also had anti-Fya and possibly Cw.

From 38 weeks gestation we kept 4 R1R1 K- Fya- units crossmatched in case of emergency. These were compatible.

4 days later the sample had a positive DAT and all units were incompatible. The patient delivered before we could get the sample referred to the NHSBT lab in the UK.

The baby typed as R1r K-. The baby had a weak positive DAT so Fya antigen typing was not officially performed ( I did the test and am certain It was Fya-)

So, my questions are; How can the anti-K and anti-Fya be stimulated by this fetus? Has anyone else seen this happen?

I was hoping to present a simple(ish) talk on anti-f to the multi-disciplinary on-call team at my hospital but don't want to scare them!



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Best guess is that the antigenic stimulation (at least primary) was not the fetus.  Sharing needles, tattooing, blood sharing ceremonies and transfusions the patient was not aware of may have been the sources of stimulation of the primary immune response.  Pregnancy stimulates Type 2 immunity (B cells mostly) which may increase the detectability of previously existing antibodies, at least in theory.

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