MadSci Network: Genetics

Re: I have AB+ blood but also have the 'little' c antibody, What does this mean

Date: Tue Apr 3 21:02:47 2001
Posted By: Michel Ouellet, Grad student in Microbiology / Immunology
Area of science: Genetics
ID: 985408630.Ge

Hello Jackson,

The ABO system and the Rh system of blood typing refer to 
specific types of sugar (not like the sugar you find in candies but 
they are sugars nonetheless) that are present on the proteins expressed on 
the surface of your red blood cells.

These proteins are called glycoproteins (glyco means sugar) and they 
represent targets for the immune system.  Your immune system is accustomed 
to your specific glycoprotein expression.  That is why your immune system 
do not react against your blood cells.  If, however, you receive blood that 
do not match your blood type, the received red blood cells will express a 
different pattern of glycoproteins and your immune system will try to 
destroy them as they are viewed as "different" and maybe harmful to you, 
much like a bacteria.

You have 23 pairs of chromosomes.  On one specific pair of chromosome is 
found the gene responsible for determining your blood type.  You can 
have the A or B gene responsible for the expression of the glycoproteins 
"A" or "B" or you can have no gene (which is represented by O) .  Since you 
have two chromosomes in that pair and one came from your mother and the 
other from your father, your blood type will come from a combination of 
possibilities. For the ABO system, there are six possibilities.  You can be 
AO or AA (blood type A), BO or BB (blood type B), OO (blood type O) or AB 
(blood type AB).  For example if your mother and father are really of blood 
type A, they could be either AA or AO themselves, which mean that they 
could not have had an AB child like you (see examples at the end of the 
answer).  They would have had children of type A or O only.  Don't panic 
though!  This could easily be a mistyping of their blood or yours or it 
could be that they think they are of A type while they are not really (one 
of them is probably B or AB).

As for the Rh antigen, it is another type of sugar and it refers to the RhD 
antigen.  Two other Rh antigens exists, the Rhc/C and Rhe/E antigens.  So 
it appears that you are AB+ (which means you are of blood type AB and 
express RhD on your cells) and you also are Rhc positive.  If your husband 
is not Rhc positive (80% of men are Rhc positive but he has a 20% chance of 
being either RhC or Rhe/E) then your child could express an antigen that is 
different of yours and thus be recognized as "different" so that your 
immune system would attack it and your body would thus reject it.  This 
condition can be treated (normally) so ask your doctor if this could have 
been prevented with medication.

Finally, here is an interesting web site on blood type and pregnancy 

I hope this answered some of your questions,



Here is a checker board using Mendel genetics that can help figure out your 
blood type.
A female that is of blood type AB mate with a male of blood type A (AO); 
their offspring would have 50% chance of having blood type A, 25% chance of 
being blood type B, and 25% of being blood type AB
          A         B

     A    AA        AB


     O    AO        BO

A female of blood type B (BO) mate with a male of blood type A (AA); their 
offspring would have 50% chance of having blood type AB and 50% chance of 
being blood type A.

          B         O

     A    AB        AO


     A    AB        AO

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