Fate of intravenously injected Mycoplasma arthritidis in rodents and effect of vaccines.

Virulent Mycoplasma arthritidis strain 158 P10 was rapidly eliminated from the peripheral circulation of rats and mice during the first 2 h after intravenous injection of the organisms. Characteristically after this time, the numbers of viable organisms remained remarkably constant through 48 to 72 h. The inability to clear the remaining mycoplasmas was not due to reticuloendothelial blockade but appeared to indicate the presence of a certain number of cells which were resistant to the clearance mechanism. Rat blood was usually devoid of mycoplasmas at 6 days and mouse blood was sterile by 14 days. An occasional transient mycoplasmemia occurred after these times. Avirulent M. arthritidis strain H606 was cleared more rapidly from rats in which it is non-arthritogenic. Different, but characteristic, clearance curves were obtained in mice using M. hominis, M. bovirhinis, and M. pulmonis. Active immunization procedures resulted in enhanced clearance of virulent M. arthritidis from rats. These procedures were less successful in mice. The results of passive immunization of normal rats and mice using convalescent serum indicated the presence of a serum factor which greatly enhanced clearance from rats but had only minimal effects in mice. This serum factor could not be correlated with metabolic-inhibiting antibody. Lymphocytes taken from convalescent rats enhanced the clearance rates of recipient rats. Mouse convalescent lymphocytes were without effect. The results indicated that mice are less able to control long-term infection by M. arthritidis than are rats.