MAC-PPD induces TNF release from monocytes through the CD14 pathway. Monocytes from healthy donors were stimulated with MAC-PPD for 8 hours, and supernatants were analyzed for bioactive TNF. (A) MAC-PPD induced TNF production from monocytes in a dose-dependent manner. (B) The LPS-neutralizing CD14 MoAb 3C10 (10 μg/mL) inhibited the stimulatory effect of MAC-PPD, in contrast to the control MoAb 6H8. Incubation of MAC-PPD together with recombinant sCD14 (100 ng/mL) led to a significant increase in TNF production from the monocytes. 0 means unstimulated cells. The mean of triplicates ± SD is shown; data are from one experiment representative of four performed.