Evidence for suppressor cell activity associated with depression of contact sensitivity in Pseudomonas aeruginosa infected mice

Pseudomonas aeruginosa infection depresses contact sensitivity to 2-phenyl-4-ethoximethylene-oxazolone (oxazolone), and enhances the antibody response to sheep erythrocytes (SRBC) in the mouse. Anti-oxazolone antibody titres were found not to be significantly different in infected and uninfected animals; thus, the major circulating classes of antibodies do not seem to be responsibile for the observed depression of skin reactivity. Low dose (20 mg/Kg) cyclophosphamide (CY) pretreatment induced a further potentiation of antibody response to SRBC, and prevented depression of contact sensitivity in infected mice. On the other hand, when infected animals were pretreated with high doses (200 mg/Kg) of CY, antibody production was completely suppressed, whereas contact sensitivity was unaffected. Since CY treatment is known to selectively inhibit B lymphocytes, and since it can abrogate the infection-induced depression of reactivity to oxazolone, it is suggested that suppressor cells, which may have B-cell characteristics, are stimulated during P. aeruginosa infection in the mouse.