The proportion of two b locus allotypic determinants in rabbit antisera raised against pneumococcal polysaccharide SSS 3 antigen.

An agar gel radial diffusion technique has been devised to examine the amount of IgG and relative amounts of As 4 and As 5 in the sera of twenty heterozygous As/4,5 rabbits immunized with Type III pneumococci. Serial absorption of the sera with the polysaccharide SSS III antigen before reaction with anti-IgG and anti-allotypic sera was used to show how much specific IgG antibody was present in each serum and the distribution of this antibody between molecules bearing one or other or neither of the allotypic determinants. The results indicate that anti-SSS III antibody generally occurred as As 4 rather than As 5 molecules although in some animals this preference was reversed. Non-allotypic (b-minus) molecules contributed significantly to the antibody response.