Experimental Mycoplasma pulmonis infection of rats suppresses humoral but not cellular immune response.

Humoral antibody response to sheep red blood cells and cellular immune response to bovine serum albumin were studied in Mycoplasma pulmonis infected, adult, male Sprague-Dawley rats. The hemagglutinating antibody response to sheep red blood cells was evaluated at 0, 3, 5, 7, 14, 21 and 28 days postinfection. Antibody titers during all days postinfection were depressed significantly (p less than 0.05) in infected rats as compared to noninfected controls. Cellular immune responses were evaluated by a delayed hypersensitivity response. Rats were sensitized at 0, 3, 5, 7, 14, 21 or 28 days postinfection with bovine serum albumin and challenged with heat aggregated bovine serum albumin 7 days later. Cell-mediated immune responses in infected rats were not significantly different at any point from controls. These results indicate that M. pulmonis infection in rats suppresses the humoral antibody response to sheep red blood cells, but not the cellular immune response to bovine serum albumin.