The influence of genetic factors on the immune response as judged by pneumococcal vaccination of mono- and dizygotic Caucasian twins.

Eighty-four mono- and dizygotic Caucasian twins randomly chosen, except for age and sex distribution, were vaccinated with a 23-valent pneumococcal vaccine. Blood samples were drawn before and after vaccination and the concentration of IgG, IgG1 and IgG2 pneumococcal antibodies was measured using an ELISA technique which only detects type-specific capsular antibodies, since C-polysaccharide antibodies in serum were removed. A significantly closer correlation was found regarding mean IgG and IgG2 antibody concentrations after vaccination in mono- compared with dizygotic twins, and this correlation was seemingly type-specific. Since environmental factors in our study population should not contribute more to the immune response in one type of twins compared with the other, we conclude that genetic factors influence the IgG and IgG2 antibody response to pneumococcal vaccination, and that this influence seems to be type-dependent.