Re: How can my father be a non secretor of B+ blood type when he is o+

Hi Tasha:

You seem to have a good idea about how blood types work, so I'll skip the introduction.

If your mother has type A blood, and your father type O, one would indeed expect you to have either type A or O.
I put your question out to some other moderators here at MADSCI who know a lot more about blood types than I do, and they came up with the following physiological reasons that your blood types could be different (in more-or-less decreasing likelihood):

• You, your mother or father were mistyped (maybe something like a 1 in 100 chance).
• Your father types as O, but actually has an A or B gene. This is caused by malfunctions in the "H" antigen (which gets modified by the products of the A and B genes to produce the A or B antigens - more on that here). This happens when:
  -There are two defective copies of the H antigen (the Bombay phenotype).
  -The H antigen is expressed weakly (para Bombay).
  -The H antigen is not secreted into bodily fluids (non secretors).
  An antigen blood test will indicate an O phenotype for Bombay and para-Bombay. An antigen test on saliva (the sort done in public schools, with seed extracts) will indicate an O phenotype for non-secretors. DNA tests could accurately determine the genotype.
• Mutation in an inherited O allele (or inactive "B allele" that is phenotypically "O") to an active B (unlikely).
• There are rare single-gene AB+ individuals where the A-galatosyltransferase can also produce the B-type chains. In even rarer cases, a subset of these individuals are only weakly B+, and may type as A+ with standard procedures.
• Rare conditions can produce a false B reactions - for instance, certain types of colon cancer shed B antigens on glycolipids into the circulation where they may be adsorbed onto red blood cells. Severe bacterial sepsis (infection in the blood) can sometimes produce false-B (I hope that is not the case).

I hope that helps,
Rob Campbell, with lots of help from Steve Mack and Lynn Bry