THE INFLUENCE OF GENETIC-FACTORS ON THE IMMUNE-RESPONSE AS JUDGED BY PNEUMOCOCCAL VACCINATION OF MONOZYGOTIC AND DIZYGOTIC CAUCASIAN TWINS

Eighty-four mono- and dizygotic Caucasian twins randomly chosen, excep t for age and sex distribution, were vaccinated with a 23-valent pneum ococcal vaccine. Blood samples were drawn before and after vaccination and the concentration of IgG, IgG1 and IgG2 pneumococcal antibodies w as meaured using an ELISA technique which only detects type-specific c apsular antibodies, since C-polysaccharide antibodies in serum were re moved. 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 contr ibute more to the immune response in one type of twins compared with t he 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.