“…GM allotypes are restricted to one subclass and located on the heavy chains of the IgG1: G1M(1,2,3,17), IgG2: G2M(23) and IgG3: G3M (5,6,10,11,13,14,15,16,21,24,26,27,28). Generally, the GM system is not fully explored, due to the reading difficulties in the classical method of agglutination on slides or microtiter plates and to the difficulty in finding good typing reagents for certain specificities.…”