Pseudomonas aeruginosa infection depresses contact sensitivity to oxazolone by enhancing suppressor cell activity

The depression of contact sensitivity to oxazolone in mice infected with Pseudomonas aeruginosa was studied. In oxazolone-sensitized mice, P. aeruginosa infection affects cell proliferation in the lymph nodes draining the site of sensitization. This impaired cell proliferation does not seem to be due to an altered lymphocyte reactivity, since lymph node and spleen cells from infected animals show a normal mitotic responsiveness to both T and B cell mitogens. In addition, the draining lymph nodes and spleens of mice exhibiting a depressed response to oxazolone contain a cell population able actively to suppress the response to the same antigen of syngeneic recipients sensitized immediately before the cell transfer. These suppressor cells require antigenic stimulation and appear to act on the induction phase of contact sensitivity.