IgG subclasses of pneumococcal antibodies--effect of allotype G2m(n).

Antibody responses to three pneumococcal polysaccharides (types 3, 14, and 18C) were analysed after vaccination with a 23-valent polysaccharide vaccine. Antibodies to all three polysaccharides could be detected before immunization. Clear cut IgG, IgA, and/or IgM antibody responses to the polysaccharides were seen in three-quarters of the vaccinees. IgG2 was the predominant and IgG1 the second most abundant subclass of anti-pneumococcal IgG antibodies both before and after the vaccination. The relative proportions of IgG2 and IgG1 antibodies exhibited a continuous variation from 1:0 to approximately 0:2. After vaccination, G2m(n)-positive homozygotes had about four times more IgG2 antibodies (anti-14 and anti-18C) than G2m(n)-negative vaccinees. Heterozygotes occupied an intermediate position. The same pattern was seen less clearly in type 3 antibodies after vaccination, and in all three antibodies before vaccination. The G2m(n) allotypes had no detectable effect on the levels of IgG1, IgG4, or IgM antibodies, and possibly a weak effect on IgG3 and IgA antibodies (G2m(n)-positive homozygotes responded strongly).