ABO Blood Groups Genetics & Inheritance

• The ABO system was first described by Karl Landsteiner in 1901
• Karl Landsteiner was able to determine 3 patterns: A, B, and C (later changed to O)
• naturally occurring: in nature, we are exposed to antigens similar to ABO; therefore we make antibodies
• The ABO genes follow simple Mendelian genetics
• ABO genes are inherited in a codominant fashion
• A and B alleles will both be expressed when present - Type AB
• AB antigen

  • in individuals with type AB, both A and B antigens are synthesized
  • typically, a gene for A antigen comes from one parent, and the gene for B antigen comes from the other parent
  • it is important to note that there are subgroups of A, B, and AB
• Bombay phenotype - antibodies to H, A, B antigens
• The h gene is very rare - lacking ABO precursor substance to H substance (H antigen)
• The H antigen serves as the precursor for the A and B antigens
• H gene is dominant to h
• If you don't have at least one H, you won't produce the transferase necessary to make H substance
• without H substance, you can't tack on the sugars necessary to make A and B antigens
• H h Genes

  • so, you can transfer A and B genes to your progeny, but they can't make A or B blood types themselves
• If type O, make antibodies A, B, and AB
• Anti-B, Anti-AB, and anti-H

  • anti-H is found in the Bombay phenotype
• A better name for naturally occurring ABO antibodies would be non-red cell stimulated antibodies