Suppression of lymphocyte proliferation by Pseudomonas aeruginosa phenazine pigments

Pseudomonas aeruginosa culture supernatants have been shown to inhibit lymphocytes proliferation as measured by [3H]TdR uptake. The phenazine pigment pyocyanine has been identified as one of the inhibitors present in those supernatants. To determine the mechanism of the inhibitory action of P. aeruginosa supernatants and pyocyanine, we studied their effect on the early stages of T-cell activation. Both P. aeruginosa supernatant and pyocyanine inhibited lymphocyte stimulation induced by the lectin concanavalin A. Analysis of Interleukin-2 receptor expression on the T-cell membrane showed that it was inhibited by both. This inhibition is dose dependent and not due to cellular toxicity. There was a parallel inhibition of growth in cell volume as well as [3H]TdR uptake. The results reported here suggest that P. aeruginosa culture supernatant and purified pyocyanine may interfere with cellular immune responses that may be necessary for eradication of chronic infection with P. aeruginosa in patients with cystic fibrosis.