CHARACTERIZATION OF THE BACTERICIDAL ANTIBODY RESPONSE AGAINST HAEMOPHILUS INFLUENZAE

Abstract

Rabbits were used in a study of the bactericidal (BC) antibody response against capsulated H. influenzae types a and b and their respective non-capsulated variant strains. Previously described methods, complement fixation and indirect hemagglutination, were used for comparison. A BC antibody response was demonstrable within 1 wk after the primary immunization against capsulated and non-capsulated bacteria. After the hyperimmunization course the BC titers against non-capsulated bacteria were about 1:4000; the BC titers against the capsulated strains reached levels of at least 1:130,000. Samples of separated hyperimmune sera showed BC activity in Ig[immunoglobulin]M and IgG fractions; the BC activity of primary response samples was demonstrable mainly in IgM fractions. The BC effect on non-capsulated bacteria of primary response samples were more heat labile than those obtained after hyperimmunization. In immune sera a crossreactive BC activity was demonstrable on non-capsulated bacteria, the titer being 32- to 64-fold lower than that of the homologous activity.