Bacteria-immune system interactions. VIII. Modulation of human cytotoxic reactions by crude lipoteichoic acid extracts of Bacillus globigii.

Crude lipoteichoic acid (LTA)1 extracts were prepared from Bacillus globigii (Bg-LTA). The addition of Bg-LTA to mixed lymphocyte reactions (MLR) produced a dose dependent inhibition of specific cytotoxic reactions and of tritiated thymidine (3H-TdR) incorporation. Much less Bg-LTA was needed to inhibit the initiation (addition at day 0) than the effector phase (addition at day 6) of the cytotoxic reactions. None of the LTA quantities used had a toxic effect on the lymphocytes. LTA pretreated stimulator cells also had a modulatory effect on the cytotoxic reactions. Stimulators pretreated with very low or very high LTA concentrations had no effect; however, pretreatment with intermediate concentrations induced a drastic inhibition of cytotoxicity. LTA pretreated stimulator cells did not significantly affect 3H-TdR incorporation. Suppression of the cytotoxic reaction could also be obtained by LTA-pretreatment of the effector cells.