The effect of Mycoplasma arthritidis infection on the kinetics of colloidal carbon clearance in mice.

The activity of phagocytes from A/J mice was estimated by the carbon clearance test following injection of Mycoplasma arthritidis. Phagocytic activity was significantly depressed 12 h post-infection (P = 0.001) and returned to normal values at 24 h. For animals examined 2 and 7 days post-infection, the overall phagocytic activity increased significantly (P < 10(-4). Phagocytic activity gradually decreased and returned to that of the control group by the end of the fourth week. The relative weights of liver and spleen were significantly increased from the 2nd day post infection (P = 0.0028 and P = 0.0014 respectively) and remained increased until the end of the experiment. The early depressive effect on phagocytic activity may be related to superantigen activity with the production of mediators such as macrophage deactivating factor. The later expansion of the macrophage population might bring about the stimulation of autoreactive clones of T and B cells and be responsible for the chronic arthritis that developed in the mycoplasma treated mice.