Stephen Jones writes, “Old blood does not always degenerate to type AB, so the Shroud of Turin’s and the Sudarium of Oviedo’s blood group being AB is significant!” Long title? Yes! But here is why and if you missed it the first time it is worth reading his latest posting:

I am reposting this excerpt from my "Shroud of Turin News for February 2012," because I have been asked a comment about the topic under my old, superseded post, "Re: Shroud blood … types as AB … aged blood always types as AB, so the significance of this … is unclear." The commenter may not have been able to find, using a search engine, my update under the uninformative title of "Shroud of Turin News."

You should also read, “A lot of old blood types as AB: Not Exactly” on this blog from this past February, which starts out as follows and contains some 53 comments:

Kelly P. Kearse, a card-carrying immunologist writes:

I appreciate the opportunity to address the issue that “All old blood types as AB”, particularly in reference to the study of the Shroud. The idea that “aged blood is degraded to (or reverts to) type AB” is rather misleading.

Blood typing is typically performed using two distinct methods that measure two very different things. First, there isforward typing, which measures the presence of specific molecules on the surfaces of red blood cells (RBC): the ABO molecules. Second, there is reverse typing, which measures the presence of antibodies in the serum (essentially the fluid component of blood), specifically the presence of antibodies to ABO blood group molecules. Both forward and reverse typing methods have been utilized in the study of the Shroud.