The I and i antigens are both considered high-prevalence antigens. The I antigen is found on the RBCs of all adults.
Anti-I autoantibodies are common among cold antibodies found in acquired hemolytic anemia. The development and production of auto anti-I can be stimulated by organisms that carry an I-like antigen on their surface, such as Mycoplasma pneumoniae. Auto anti-I can also be associated with cold agglutinin disease (CAD), Raynauds, Chronic Lymphocytic Leukemia (CLL), Non-Hodgkin's Lymphoma (NHL), and Waldenstrom Macroglobulinemia.
