Cytotoxic effect of Mycoplasma fermentans on mouse thymocytes

Abstract

The in vitro response of mouse thymocytes to various mycoplasmas was evaluated. Cultures of thymus cells from BALB mice were prepared in Earle minimal essential medium with 10% fetal calf serum. After an initial drop in viability, cell populations stabilized at approximately 105 viable cells/ml for 3 to 5 days. Concentrations of 106 to 108 colony-forming units of toxic isolates of Mycoplasma fermentans per ml killed over 50% of these cells in a dose-dependent fashion. Four other mycoplasmas (M. pneumoniae, M. hominis, M. arthritidis, and a nontoxic strain of M. fermentans) did not induce cytotoxicity of mouse thymocytes. Toxic isolates of M. fermentans multiplied in the presence of thymus cells as they were being inactivated. However, nonviable membrane preparations of these mycoplasmas were also toxic, indicating that growth of the organisms is not a prerequisite for the toxic effect. The relevance of these findings for the isolation and identification of the membrane-associated toxic factor is discussed.

Microbial surfaces in relation to pathogenicity.

“…Cell membrane fractions from M. pneumoniae were toxic to hamster tracheal cultures, in contrast to other cell fractions (65). Similar results were obtained with membrane fractions from Mycoplasma fermentans (66), and possibly the same situation occurs with M. mycoides (141).…”

The mycoplasmas.

“…Killed mycoplasma cells or fractions thereof can also be toxic to animals (94). Injection of large quantities of killed M. fermentans cells or membranes killed mice with symptoms resembling those of gram-negative endotoxemia, including thymic involution and an increase in the level of the lysosomal ,B-glucuronidase in the serum (94,97,99,100). These data could suggest that mycoplasmas possess an endotoxin resembling that of the gram-negative bacteria, as was proposed earlier by Villemot et al (337).…”

“…Our present knowledge of the mycoplasma membrane composition, however, rules out the presence of any molecules resembling the classical bacterial lipopolysaccharides (see Membrane Lipids). Hence, it is not surprising that the toxemia due to M. fermentans cells or membranes differed in some important details from that caused by lipopolysaccharides (99,100), and the Limulus amoebocyte lysate coagulation test, capable of detecting extremely low doses of lipopolysaccharide, remained negative in mice injected with M. fermentans (92). Thus, the nature of the toxic factors in M. fermentans cells and membranes is still unclear (see also Organ Cultures as Experimental Systems).…”

Respiratory infection of lambs with Mycoplasma ovipneumoniae

“…The suppressive activity on lymphocytes of both fermentative and nonfermentative mycoplasmas was dependent upon the dose and membrane protein used. This effect was varied and reversible however, depending upon species of mycoplasma and type of lymphocyte used Gabridge and Schneider, 1975). pulmonis stimulated both T and B lymphocytes of humans and rats respectively (Naot et al, 1979 a,b,c).…”