Bombay Phenotype
Physiology For A or B antigens to be expressed on RBCs, the cells must have a precursor substance—H antigen encoded by the H gene; Oh type RBCs do not agglutinate with antisera containing anti-A, anti-B, or anti-H type antibodies as they lack the H gene, and ergobstance; Oh subjects do have anti-A, anti-B, and anti-H antibodies in their serum, which may cause problems when cross-matching donors and recipients