title: Cellular basis of immune response to antigens of ABO blood-group system. Capacity to provide help during response to T-cell-dependent ABO-system antigens is restricted to individuals of blood group O.
abstract: It is postulated that the near-identity of the A and B antigens in man makes it impossible for individuals of groups A, A2, or B to provide T-cell help during a response to T-dependent non-self antigens by B2 lymphocytes. Thus, people of these groups are unable to produce immune IgG antibody. The presence of naturally occurring IgM antibody to non-self antigen from the age of 6 months is due to a separate system of T-cell-independent B1 cells which have arisen during evolution to protect the host against polysaccharide-encapsulated bacterial pathogens.
mesh_terms: D000017:ABO Blood-Group System / Q000276:immunology*; D000328:Adult; D000955:Antigens, T-Independent / Q000276:immunology*; D003429:Cross Reactions; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D007223:Infant; D008297:Male; D013601:T-Lymphocytes / Q000276:immunology*; D006377:T-Lymphocytes, Helper-Inducer / Q000276:immunology
chemical_list: D000017:ABO Blood-Group System; D000955:Antigens, T-Independent; D007074:Immunoglobulin G; D007075:Immunoglobulin M