<P> Some blood types are associated with inheritance of other diseases; for example, the Kell antigen is sometimes associated with McLeod syndrome . Certain blood types may affect susceptibility to infections, an example being the resistance to specific malaria species seen in individuals lacking the Duffy antigen . The Duffy antigen, presumably as a result of natural selection, is less common in ethnic groups from areas with a high incidence of malaria . </P> <P> The ABO blood group system involves two antigens and two antibodies found in human blood . The two antigens are antigen A and antigen B . The two antibodies are antibody A and antibody B . The antigens are present on the red blood cells and the antibodies in the serum . Regarding the antigen property of the blood all human beings can be classified into 4 groups, those with antigen A (group A), those with antigen B (group B), those with both antigen A and B (group AB) and those with neither antigen (group O). The antibodies present together with the antigens are found as follows: </P> <P> 1 . Antigen A with antibody B 2 . Antigen B with antibody A 3 . Antigen AB has no antibodies 4 . Antigen nil (group O) with antibody A and B . </P> <P> There is an agglutination reaction between similar antigen and antibody (for example, antigen A agglutinates the antibody A and antigen B agglutinates the antibody B). Thus, transfusion can be considered safe as long as the serum of the recipient does not contain antibodies for the blood cell antigens of the donor . </P>

What are the different types of blood type