DIFFERENT GM ALLOTYPE AMOUNTS IN HUMAN INTRAVENOUS IMMUNOGLOBULIN (IVIG) PREPARATIONS - SURVIVAL OF FOREIGN GM ALLOTYPES IN IMMUNODEFICIENTPATIENTS

IVIG is used as standard replacement therapy in primary antibody defic iency. IVIG consists mainly of IgG. IVIG preparations were investigate d with respect to Gm allotypes, which are characterized by various ami no acid epitopes in the constant heavy chains of the IgG subclasses Ig G1, IgG2 and IgG3. The alternative allelic Gm allotypes G1m(a) and G1m (f) of IgG1, G2m(n) and G2m('') of IgG2 and G3m(g) and G3m(b) of IgG3 were measured by sensitive competitive ELISAs for G1m(a), G1m(f), G2m( n) and G3m(b). IgG subclass levels were quantified by radioimmunodiffu sion (RID). Gm allotype quantities differed significantly in Various I VIG products, with different products having half or double the amount of the different Gm allotypes. The results show the effect of the dif ferent manufacturing processes, but also indicate different physicoche mical properties of Gm allotypes within the same IgG subclass. The dif ferent contents of Gm allotypes might be one reason for the variable l evels of specific antibodies found in IVIG products. Immunodeficient p atients with homozygous expression of Gm allotypes from IGHCG1 IGHCG2 and IGHCG3 were tested after infusion of foreign Gm allotypes. A prolo nged survival was found for the G2m allotype, G2m(n), compared with G1 m, allotypes. Different half-lives were found for the alternative G1m( a) and G1m(f) allotypes, within the same IgG1 subclass.