Malcolm Needs

Two things. Firstly, although the anti-M may be "naturally occurring", it need not necessarily be IgM. Many examples of anti-M, reacting in the cold and RT are, in fact, agglutinating IgG (a bit like ABO IgG antibodies and anti-P in the DL Test). In addition, maternal IgG antibodies are actively transported across the placenta and, as a result, the baby ends up with a higher concentration of some IgG specificities in their circulation than is in the mother at birth. As the anti-M in the baby's circulation is so weak (showing dosage), it could be that it is of maternal origin, but that it is so weak now in the mother that it is undetectable in her plasma using normal serological techniques. Secondly, some precocious babies are (rarely) known to produce their own IgM antibodies at birth (this can be proved by the babies producing an ABO antibody that cannot have come from the mother - say a group O baby with anti-B in the plasma, from a group B mother, or by looking at the Gm and/or Km types of the immunoglobulins - see, for example, Toivanen P, Hirvonen T. Iso- and heteroagglutinins in human fetal and neonatal sera. Scand J Haemat. 1969; 6: 42-48), so it could be the baby's own antibody, despite what I said above! Lastly, and this came to me as I was typing (hence a third point), is the mother of the baby of Japanese origin? The only reason I ask is that, if she is, be a bit careful, as anti-M of low titre has been known to cause a sort of delayed HDFN in this ethnicity (see Yasuda H, Ohto H, Nollet KE, Kawabata K, Saito S, Yagi Y, Neggishi Y, Ishida A. Hemolytic disease of the fetus and newborn with late-onset anemia due to anti-M: a case report and review of the Japanese literature. Transfusion Medicine Reviews 2014; 28: 1-6. doi: 10.1016/j.tmrv.2013.10.002). Incidentally, although I have seen anti-A or anti-B in a newborn's plasma, I have never seen an anti-M.

They always used to be, but having retired in October 2016, I am no longer sure that they are. Anyone else know?

I think it more likely that the donor is expressing an antigen, such as T, Tn, Tk, Cad, etc, possibly as the result of a subclinical infection if this has not been seen before with his/her blood (which would rule out Cad). Have you tried testing it with a lectin panel?

Couldn't agree more, particularly, certainly in my own experience, many inspectors have a minimal amount of experience in the field (particularly Reference Laboratories), but feel they have to comment to justify their employment, even though they don't actually understand or know what they are talking about; not all, but far too many.

The Blood Bank Guy is the excellent Dr Joe Chaffin. They are one and the same.

Welcome Melissa Harp.

Odd ball? I'll have you know I am capable of making an anti-Ch!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Welcome EmeraldM.

Anti-M that reacts at STRICTLY 37oC can most certainly be clinically significant. Antibodies directed against, for example, antigens to the Chido/Rodgers Blood Group System, the JMH Blood Group System and the Knops Blood Group System, however, are NEVER clinically significant, although those within the Chido/Rodgers Blood Group System can, on very rare occasions, cause an anaphylaxis type reaction.

Welcome sbraden.

Welcome Sahal Alawi.

Welcome Louise Rogers.

There are quite a few (too many to mention here). Can I cite for you, NHSBT Guidelines in your search engine, followed by looking for SPN214/3 (SPN stands for specification) and up will pop a document entitled "The Clinical Significance of Blood Group Alloantibodies and the Supply of Blood for Transfusion., written by my very good friend Nicole Thornton, Head of Red Cell Reference at the International Blood Group Reference Laboratory in Filton (Bristol) in the UK. If I tell you that the document is 22 pages long, you may understand my first sentence!

Welcome Sara Guerinoni.

Welcome labboy.