Two human examples of multiple-allele<span> genes are the gene of the ABO blood group system, and the human-leukocyte-associated antigen (HLA) genes. The ABO system in humans is controlled by three </span>alleles, usually referred to as IA, IB, and IO<span> (the "I" stands for isohaemagglutinin).</span>
Anti-bodies. This is not a hard question to answer, as you can just copy/paste the question into a search engine to get an adequate answer.
The 3rd one I think not really sure
