MadSci Network: Medicine
Query:

Re: I undrstand about blood types but what does positive and negative mean ?

Date: Thu May 11 21:46:50 2000
Posted By: M. Salik Jahania, M.D., Suregry, Cardiothoracic, University of Kentucky
Area of science: Medicine
ID: 957291288.Me
Message:

Well if you understand the blood types then this will be easy to explain.
People have 2 basic set of proteins on their cells, including blood cells 
and other cells in the body. These proteins are called either the A 
proteins or the B proteins. People inherit one protien from their mother 
and the pther from their father.
These can be in any combination. Any cell may have an A from the father 
and B from the mother. This would make for the blood group AB. If the 
person does not get an A from the father but gets B from the mother they 
would have the Blood group B, Since the A from the father is absent. 
Similarly if a person does not get B from the mother but gets A from the 
father than his blood group would be A. If neithr A or B protiens are 
inherited then th eperson is stated as having O blood type meaning (no 
protein from the Ab system).
Another set of proteins are also found on the blood cells. These were 
frist found is rhesus species of monkeys. Hence they were named the rhesus 
protein. If a person has rhesus protien they are called positive. If they 
do not inherit the rhesus protein from their parents then they will not 
have the rhesus gene to make the rhesus perotein and the cells will not 
have the rhesus protein. hence they will be negative for the rhesus 
protein.
This rhesus (rh shortform) system of classification is called the Rh 
typing of blood. Combined with the ABO system it is often stated that the 
person is AB-Rh negative meaning they have both the A and B protein of the 
AB system and they do not have the rhesus protein. On the other hand if a 
person had only the B protien from the ABO system and had a rhesus protien 
then they would be clssifid as B-positive.
 Hope this helps.



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