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Archiver > GENEALOGY-DNA > 2001-10 > 1003483020


From:
Subject: Re: [DNA] bone marrow donor tests
Date: Fri, 19 Oct 2001 05:17:00 EDT


In a message dated 10/17/01 5:55:46 PM Pacific Daylight Time,
writes:


> As a participant in the Bone Marrow Donor program my blood was screened.
> This screening process was done 9 years ago, and recently, I asked for my
> results. They gave me a series of numbers and letters that mean nothing to
> me. They are: A11,30; B18,55; DR03AD,04HR
> I would appreciate it if anyone could tell me what these mean.

The initial letters (A, B, DR) are names for some of the genes in the Human
Leukocyte Antigen (HLA) system. Leukocytes are white blood cells, and it's
important to match white blood cell types for bone marrow and organ
transplants, just like you match red blood cell types for transfusions. (The
A and B HLA genes are not related to the ABO red blood cell types; it's just
handy to use letters of the alphabet for naming things, like mtDNA
haplogroups.) The numbers tell you the variation (allele). I don't know about
the letters after the numbers (AD, HR).

You inherit one copy of each gene from your father and one copy from your
mother. The genes are close together on one chromosome, so they are usually
inherited as a package, but you can't tell what's in the package without
testing more family members. For example, you don't know if the person who
gave you the A30 allele gave you the B16 or the B55 allele. But if enough
family members are tested, you might discover that no one on your mother's
side had A30 or B18, and everyone on your father's side who had A30 also had
B18. Then you could deduce that A30 and B18 were on the same chromosome and
came from your father. In turn, that "package" would have come from one of
your 2 paternal grandparents, one of your 4 paternal great-grandparents, etc.

For a diagram of alleles and how they are passed from parent to child, see

http://www.hokkaido.bc.jrc.or.jp/laboratory/laboratory500_eng.htm

The varioius alleles occur with different frequencies around the world. L.
Luca Cavalli-Sforza's book "The History and Geography of Human Genes" (the
big hardbound version, ISBN 0-691-08750-4) has maps for HLA-A and HLA-B. It
looks to me like HLA-A30 and HLA-B18 both occur most frequently in Sardinia,
so I'd bet they are on the same chromosome. HLA-A11 is most frequent around
the Gulf of Siam. HLA-B55 is not covered, but I found a table of "splits"
which showed that B55 is a subtype of B22. B22 is most frequent in some of
the Pacific Islands.

These geographic locations are Just For Fun, like the Mitochondrial DNA
Concordance, and they may not make any sense at all to you in connection with
your own ancestry. The "high" frequencies don't necessarily mean that your
ancestors ever lived in those locations. Your alleles can be found at lower
frequencies in many other parts of the world.

I've been interested in the HLA system for quite some time. It seems like it
does have some potential for linking family trees together, although there's
only a 50% chance of inheriting a specifc package from the previous
generation. I don't know if everyone who registers as a bone marrow donor can
get their HLA results, but it seems to be common. Perhaps even people who
volunteer as apheresis donors get HLA test reports. In apheresis collections,
your red blood cells are returned to you, and the blood bank keeps the white
blood cells and platelets. People who need many platelet transfusions seem to
do better if HLA types match.

Maybe we'll see a little wave of people signing up to be bone marrow or
apheresis donors now! You can do a good deed while satisfying curiosity about
your HLA types.

Ann





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