krista@ihlpa.ATT.COM (Anderson) (11/03/88)
<>
I have two blood questions:
1. In my parents' family of 5 children, 3 are Rh positive, 1 is Rh
negative, and 1 says he used to be positive, but now is tested as
negative. I don't think it's possible to change Rh factor, is it?
2. I read in _Encyclopedia_Britannica_ that the A factor helps give
immunity against smallpox and the B factor helps protect from
certain kinds of cancer.
Since I've read about Native Americans and ethnology, I'm
surprised I've never heard this before. Incidence of types A and B
is very low among Native Americans, and by 1700, 80-90% of Native
Americans had died of various European diseases, esp. smallpox.
The encyclopedia went on to say that the Blackfeet tribe had
about 59% type A at the time that it was measured. The authors
hypothesize that a smallpox epidemic devastated the majority of
people with O type. I have read from other sources that this tribe
has a high incidence of type A, unlike any other American tribe.
My question is, has anyone else read about type A to smallpox
correlation? One doesn't usually doubt the _Encyclopedia_Britanica_!
If anyone is in the know, it would be interesting to see the
relationships of blood factors to phenotypic expressions.
Thanks in advance. Krista A.jca@drutx.ATT.COM (jill c. arnson) (11/04/88)
in article <10241@ihlpa.ATT.COM>, krista@ihlpa.ATT.COM (Anderson) says: > Xref: drutx sci.bio:1617 sci.med:8068 > > <> > I have two blood questions: > > 1. In my parents' family of 5 children, 3 are Rh positive, 1 is Rh > negative, and 1 says he used to be positive, but now is tested as > negative. I don't think it's possible to change Rh factor, is it? > One possiblity is that the "used to be positive" sibling has a D variant called Du. What this means is that part of the mosiac that makes up the D antigen is missing. The fact that a person is 'Du positive' can be confusing is some cases as some people call this D negative, Du positive, where others simply call this D positive. Because of this I would see if you other negative sibling be retested, looking especially for the Du mosaic. It DOES make a difference. -- jill c. arnson (att/ulysses/mtuxo)!drutx!jca AT&T Bell Labs, Denver; (303)538-4800 *** "When you climb high, remember that the beauty you see is only an illusion created by God to keep your sanity."
emigh@ncsugn.ncsu.edu (Ted H. Emigh) (11/04/88)
In article <10241@ihlpa.ATT.COM> krista@ihlpa.ATT.COM (Anderson) writes: >1. In my parents' family of 5 children, 3 are Rh positive, 1 is Rh >negative, and 1 says he used to be positive, but now is tested as >negative. I don't think it's possible to change Rh factor, is it? No, but the testing procedures are not 100% accurate. It is possible to test Rh+ one time and Rh- another time. >2. I read in _Encyclopedia_Britannica_ that the A factor helps give >immunity against smallpox and the B factor helps protect from >certain kinds of cancer. The smallpox virus crossreacts to some extent with anitbodies to group A antigens because of similarity in antigenic structure. Therefore, type A people would produce antibodies to smallpox less effectively than people who are not A or AB. This may explain why there is a very high frequency of type O in Iceland (Ann. Hum. Genet. 1985, 49:275). There is a connection with virtually all antigenic blood types (as well as the histocompatibility loci) and various diseases -- most likely because of the antigenic similarities. In most cases, the effect is slight -- with notable exception for HLA. > Since I've read about Native Americans and ethnology, I'm >surprised I've never heard this before. Incidence of types A and B >is very low among Native Americans, and by 1700, 80-90% of Native >Americans had died of various European diseases, esp. smallpox. > The encyclopedia went on to say that the Blackfeet tribe had >about 59% type A at the time that it was measured. The authors >hypothesize that a smallpox epidemic devastated the majority of >people with O type. I have read from other sources that this tribe >has a high incidence of type A, unlike any other American tribe. This appears to be backward from the way it should be. > My question is, has anyone else read about type A to smallpox >correlation? One doesn't usually doubt the _Encyclopedia_Britanica_! >If anyone is in the know, it would be interesting to see the >relationships of blood factors to phenotypic expressions. Any good Human Genetics Textbook will give examples. Examples of good textbooks are: Hartl, Human Genetics Sutton, An Introduction to Human Genetics (4th Edition) Another good book is by Mutolsky, but I seem to have lent my copy, so I don't have the title -- no doubt it is "Human Genetics" -- Ted H. Emigh, Dept. Genetics and Statistics, NCSU, Raleigh, NC uucp: mcnc!ncsuvx!ncsugn!emigh internet: emigh@ncsugn.ncsu.edu BITNET: emigh%ncsugn@MCNC.UUCP or emigh%ncsugn@ncsuvx.ncsu.edu
krista@ihlpa.ATT.COM (Anderson) (11/10/88)
<>
Thanks for the replies on blood questions. My sibling was
probably wrongly tested as Rh positive at one time.
As for blood type A helping one to be immune to smallpox,
after reading various comments, I've decided not to believe it,
unless some source superior to the encyclopedia publishes it.
The fact that the Blackfeet have 59% type A, whereas the other
tribes north of Mexico have 1-35% type A, can be explained in other
ways. There was indeed a smallpox epidemic in 1837 among the
Blackfeet and Blood of Montana/Canada. There were French traders in
the area earlier than that. So, perhaps the French intermarried and
passed on smallpox immunity as well as higher incidence of type A
blood before the epidemic. So, it could be coincidental.
On the other hand, for all we know the tribe may have had a high
incidence of type A before the epidemic and before the French! :-)
So I guess it's just one of those mysteries that makes Native
American studies so fascinating.
Krista A.