Stephen Jones, as always, responded to a reader of his blog with wonderful thoroughness. He received an email asking about the claims that the blood on the shroud is type AB and why that may or may not be significant and why that might be a false reading. I received, essentially, the same email. I was traveling and away from my files and thus unable to respond. Stephen, thankfully, did help. Read his posting,
Back in October, I did write something on the subject as a by-the-way comment to a much longer off-topic posting on evolution, Open Letter to Another Blogger. I wrote:
BTW: You make a good point about blood type AB. Al Adler, a blood specialist from Western Connecticut State University, and another Shroud scientist, pointed out that all old blood tended to test AB because the compounds that generated the test response were also in the cell walls and if the walls degraded the blood started to test AB. But it was possible, he felt, to discern false AB positive readings from real AB type readings.
I wish I knew more about the subject.