Posted February 12, 20205 yr comment_79586 Hi! We have a patient who genotyped as A Bel. Is the Bel subgroup a complete antigen or partial? The patient expresses extremely low levels of B, would it be safe to transfuse with AB blood? The patient has no detectable anti-B occurring naturally. As far as I can tell by the litterature, Bel cells are not agglutinated with anti-B (but do bind to them)? We will, of course, have our doctor decide what recommendations to give, but I would like to know how other treat these patients as it´s a first for us. Please explain it like I´m five :)
February 12, 20205 yr comment_79588 Putting aside the A antigen for the moment, which is probably "normal" in the case of your patient, it is not the B antigen that is abnormal in the case of a Bel person, but the 3-alpha-galactosyltransferase enzyme (the direct gene product of the ABO gene) is less active than normal, due to a mutation in the gene. The actual carbohydrate residue that is on the red cell is "normal" - just less of it. In addition, there is competition between the "A-transferase" and the "B-transferase" for the H-backbone. In the case of your patient, the "A-transferase" will "win" this competition and this will accentuate the weakening of the B antigen even further - but the actual structure of the B antigen will be the same as the normal B antigen - just fewer in number. This explains why there is no anti-B present in your patient's circulation. This (rather long-winded) explanation should serve to prevent you worrying about giving your patient group AB blood should they require a transfusion.
February 13, 20205 yr Author comment_79599 Thank you! I found it difficult to find general recommendations regarding Bel. I discussed it with our reference lab just now, they weren't convinced about the transferase's ability to produce a complete antigen, since the expression was extremely low. I thought, as you say, that the absence of anti-B would implicate a normal B antigen but they were unwilling to recommend anything but A or 0 blood. This particular patient has a mutation not earlier documented, so it might be their cause for taking extra caution. Thank you for some great insight! It's an amazing forum for gaining new knowledge!
February 13, 20205 yr comment_79600 52 minutes ago, Emelie said: Thank you! I found it difficult to find general recommendations regarding Bel. I discussed it with our reference lab just now, they weren't convinced about the transferase's ability to produce a complete antigen, since the expression was extremely low. I thought, as you say, that the absence of anti-B would implicate a normal B antigen but they were unwilling to recommend anything but A or 0 blood. This particular patient has a mutation not earlier documented, so it might be their cause for taking extra caution. Thank you for some great insight! It's an amazing forum for gaining new knowledge! I don't want to interfere, but have you thought about sending a sample to Martin Olsson's laboratory in Lund? He is the world authority on the ABO gene.
February 13, 20205 yr Author comment_79602 It's Martin who's analyzed it (we've sent new samples so they can confirm their findings) We'd better do as they say, then 😄 Edited February 13, 20205 yr by Emelie
February 13, 20205 yr comment_79604 3 hours ago, Emelie said: It's Martin who's analyzed it (we've sent new samples so they can confirm their findings) We'd better do as they say, then 😄 You bet! There is NOBODY better! ANYWHERE!
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