Immunofluorescent characterization of lymphocytes in lungs of rats infected with Mycoplasma pulmonis.

Immunofluorescence was used to determine the relative percentages of T and B lymphocytes found in the lungs of normal and Mycoplasma pulmonis-infected F344 rats. Lymphocytes recovered from controls were approximately 25% T, 25% B, and 50% unclassified mononuclear cells. Infected animals had a 2.6-fold greater number of T cells and IgA-bearing cells, and a 1.6-fold greater number of unclassified mononuclear cells. These studies show that M. pulmonis infection significantly alters lung lymphocyte populations both quantitatively and in subpopulation distribution. Therefore, future studies of rat lung lymphocytes should utilize animals known to be free of this ubiquitous respiratory pathogen.