Production of potent immunoglobulins by group A streptococcus for antibody dependent cell-mediated cytotoxicity in mice.

Antibody-dependent cell-mediated cytotoxicity (ADCC) through serum, which was obtained from B6D2F1 mice pretreated with heated group A streptococci, and spleen cells of normal B6D2F1 mice was examined for different kinds of mouse tumor cell line by using methods to estimate specific 51Cr-release from each 51Cr-labeled target cells. Serum obtained from mice 14 days after the injection with heated streptococci was evidently potent to cause ADCC for all tumor cells tested. When the experiments were carried out under the condition which E/T ratio is 50:1, specific 51Cr-release from each target cells were about 32% for L1210 cells, about 12% for MOPC 31C cells, and about 23% for MH 134 and about 10% for P 388 cells, respectively. Meanwhile, serum obtained from either BCG-injected mice or normal mice was not so much potent for these tumor cells. Experiments to identify immunoglobulin subclasses participating in antibody-dependent cell-mediated cytotoxic reactions clearly showed that only IgG2a immunoglobulin was effective to induce cytotoxic reaction. All classes or subclasses of serum immunoglobulins from mice pretreated with group A streptococci were estimated using single radial immunodiffusion plates which were incorporated with monospecific rabbit antiserum for each classes or subclasses. Results showed that either IgM or IgG2a levels were significantly increased 7 days and 14 days after the injection, but other immunoglobulin classes or subclasses did not. A possible consideration on the production of immunoglobulin to cause ADCC in mice treated with heated streptococci was discussed.