Development of Cell-Mediated Hypersensitivity in Guinea Pigs following Infection with <i>Nocardia asteroide</i><i>s</i>

Abstract

Partially purified protein antigen which was prepared from cells of <i>Nocardia asteroides</i> was used to assess the immune responsiveness of guinea pigs inoculated subcutaneously with living <i>N. asteroides</i>. Cell-mediated reactivity, as measured by in vitro lymphocyte transformation of and blastogenic factor production by lymph node cells as well as a delayed skin reaction, appeared clearly at 1 week after <i>N. asteroides</i> infection, when an early abscess was formed at the inoculated site. The in vitro proliferative response of lymph node cells reached a maximum at 2 weeks at which time the lesion of the inoculated site showed central suppuration surrounded by epithelioid and giant cells. The lymphocyte transformation response then declined rapidly but a significant response continued until 6 weeks after infection. The production of blastogenic factor was maximum at 3 weeks, but continued till 6 weeks. A high level of skin reactivity was maintained until 6 weeks. By 6 weeks after infection the lesion at the inoculated site usually resolved and disappeared. Thus, enhancement of cell-mediated reactivity coincided with the time of granulomatous conversion of an early suppurative abscess at the site of inoculation of <i>Nocardia</i> organisms. In studies on the lymphocyte proliferative response in vitro of <i>N. asteroides</i>-infected animals, purified lymph node T cell populations failed to respond to <i>Nocardia</i> antigen, but they could be induced to proliferate in the presence of autologous macrophages or B cells. Purified B lymphocytes, though unresponsive to <i>Nocardia</i> antigen by themselves or following the addition of macrophages, were stimulated by <i>Nocardia</i> antigen in the presence of T cells. The proliferative response of lymph node cells to <i>Nocardia</i> antigen seems to be the result of a collaborative event that occurs between T cells and macrophages or T and B cells.