[Stimulatory effects of a streptococcal protein, preabsorbing antigen (PA-Ag), on human lymphocytes]

The possible role of a streptococcal protein, preabsorbing antigen (PA-Ag), in human cellular immunity was examined by a lymphocyte stimulation test. Lymphocytes were obtained from 12 healthy adult donors who had no history of acute poststreptococcal glomerulonephritis nor of other renal diseases, and from the blood of 4 umbilical cords. In addition to PA-Ag, pre-purified material from ruptured cell supernatant (RCS) was also tested for lymphocyte stimulation, and their time-response relationships were compared to those with stimulation by phytohemagglutinin (PHA), a nonspecific mitogen. Results showed that the lymphocytes of the 12 adult donors proliferated in a dose-dependent manner in response to PA-Ag or RCS stimulation. In the response to these proteins, the peak responsiveness of lymphocyte proliferation was characteristically seen between the 5th and 7th days of cultivation, while it was seen between the 3rd and 5th days in PHA stimulation. Surprisingly, lymphocytes derived from umbilical cord bloods also significantly proliferated in the presence of PA-Ag. These results indicate that PA-Ag stimulates human lymphocytes to proliferate in a different manner than when stimulated by PHA, and the induction of the stimulatory effects is not dependent on antigen-specific response, since it does not require pre-sensitization of the host.