Mice treated with antilymphocyte serum (ALS) intraperitoneally and challenged by the same route with Pseudomonas aeruginosa demonstrated an enhanced mortality and a decreased ability to remove viable bacteria from the peritoneal cavity compared with mice treated with normal rabbit serum (NRS). These effects were dependent upon the concentration of bacteria injected. With an optimal concentration of bacteria a definite difference in the bacterial population of the peritoneal cavity was detectable between mice treated with either ALS or NRS. The bacteria were removed very rapidly from the peritoneal cavity of mice treated with NRS but very slowly in mice treated with ALS.
Studies of the cellular composition of the peritoneal fluid revealed that the fluid of ALS-treated mice contained half the number of leukocytes seen in the fluid of those treated with NRS.