RELATION BETWEEN LOW CAPACITY OF HUMAN SERA TO INHIBIT STREPTOCOCCAL MITOGENS AND SERIOUS MANIFESTATION OF DISEASE

The proliferative response of lymphocytes induced by a new streptococc al mitogenic factor (MF) and the streptococcal pyrogenic exotoxins (Sp e) A and B was determined in sera from 6 healthy persons. Responses we re compared to those obtained from reference serum that lacked mitogen -specific ELISA antibodies. The sera showed individual variations in t he levels of MF-and Spe-specific antibodies, as determined by ELISA. T he experiments showed that most human sera, which contained mitogen-sp ecific antibodies, could neutralize the mitogenicity of the proteins. However, there were sera that contained mitogen-specific antibodies bu t that did not inhibit the toxin-induced proliferation. Thus, the ELIS A antibody titer did not always equal the neutralizing capacity. Sera from 27 patients with group A streptococcal bacteremia had significant ly lower neutralizing ability against MF and SpeB than did sera from 2 5 uncomplicated tonsillitis cases.