Host clearance of Chlamydia from the spleen and the joint. Tissues were harvested 5 days after the induction of Chlamydia trachomatis-induced arthritis (CtIA). (a) The mean level of the splenic bacterial load for the mercuric chloride (HgCl2)-exposed rats was higher than that of controls (P < 0.005). (b) In the joint, the mean Chlamydia load for the HgCl2-exposed rats was significantly higher than that of controls (P < 0.05). Immunohistology shows more intense staining with anti-Chlamydia antibodies in the HgCl2-exposed rats (c) than controls (d) (n = 5 in each group). Original magnifications × 200. O.D., optical density.