Group A and B Subgroups
The serum of group B persons contains two antibodies: anti A and anti A1. By proper absorption, the two antibodies can be separated. Cells of group A that react with anti A1 are part of the subgroup A1. Cells that react with anti A but not with antiA1 fall into subgroups weaker than A1, thus being classified as A2.
Subgroup A1 : Makes up to 80 Percent of the A gene pool and most of the H is changed to A antigen because of the large number of antigen sites on the cells.
Subgroup A2: make up 20 percent of the A gene pool, and have less H changed to A antigen because of the smaller amount of sites on the cells compared to A1. Could produce anti A1.
*** Subgroups of B are rare in most populations. They are usually recognized by variations in the strength of a reaction with anti B. There is no reagent available to distinguish among them. The patient’s serum may contain anti B antibodies.
ABO antibodies and antigens
Antibodies produced by exposure to antigens (bacteria and plants) are not seen until four to six months old. The anti A and anti B found in the serum of a newborns is of maternal origin. In healthy individuals, ABO antibodies are always present peaking at age five to ten years.
Percentage of ABO Antigens and Antibodies in United States Populations
||Red Cell Antigens
||% of U.S. Population
||No A or B antigens
||Anti A, Anti B, & Anti A,B
||A & B
||A & A1
||Anti B (may develop anti A1)
||Anti A & Anti A1
***ABO antigen frequency can vary in other populations with different ethnic mixes.
Genotype Diet, Allergies, etc. for A1, A2, B, & O Types