THE IMPORTANCE OF G1M AND 2 ALLOTYPES FOR THE IGG2 ANTIBODY-LEVELS AND AVIDITY AGAINST PNEUMOCOCCAL POLYSACCHARIDE TYPE-1 WITHIN MONOZYGOTIC AND DIZYGOTIC TWIN-PAIRS

Eighty-two mono- or dizygotic Caucasian twins vaccinated with a 23-val ent pneumococcal vaccine, who had previously had their IgG2 antibody l evels to pneumococcus type 1 determined before and after vaccination, were included in this study. Their IgG2 antibody levels were related t o their G1m and G2m allotypes/phenotypes and their Gm amounts. Eight d ifferent Gm phenotypes were found and characteristically IgG2 antibody levels were related to them. G2m (n) homozygotic twins had significan tly higher IgG2 levels than heterozygotic twins who had significantly higher levels than G2m (-n) homozygotic twins (P < 0.05). The G1m allo type, on the other hand was without influence on the IgG2 levels and s o were the Gm amounts among G2m (n) heterozygotic twins. The IgG2 anti body avidities were not related to Gm allotypes but significantly corr elated to IgG2 levels (P = 0.05). Finally, a highly significant intra- pair correlation was found for avidity in the monozygotic twins suppor ting a genetic regulation of avidity (P < 0.002). These results may ex plain our earlier findings that IgG2 antibody levels after pneumococca l vaccination are significantly more closely correlated within mono- c ompared to dizygotic twins.