Effect ofBacillus firmus and other sporulating aerobic microorganisms onin vitro stimulation of human lymphocytes. A comparative study

B. firmus activates human peripheral blood lymphocytesin vitro. Bacteria inactivated by heat or by formaldehyde were about equally effective, stimulating the blastic transformation of lymphocytes at doses of 10–200 mg/L and Ig formation in the culture at 10–500 mg/L. The action of formaldehyde treatedB. firmus was compared with that of analogously inactivatedB. subtilis, B. polymyxa, B. coagulans, B. megaterium, B. pumilus, B. cereus andB. lentus at a concentration of 100 mg/L. All these bacilli midly stimulated blastic transformation and most of them substantially stimulated Ig formation, butB. firmus was the most efficient in stimulating the formation of Ig of all classes, in particular IgM and IgA. Its effect on Ig formation was comparable with that of PWM and was unusually high as compared with that of other bacteria.B. firmus is apparently a strong polyclonal activator of B lymphocytes. Its cells or their components could be potentially used for modulating immune reactions. The work was supported by grant no. 0679-1 from theMinistry of Health of the Czech Republic.