Figure 2. TNF- production by THP1 monocytes. (A) Cells were incubated in medium alone or stimulated with increasing concentrations of Pg LPS for 6 and 24 hrs. All treatments induced significant increases (P < 0.05) in TNF- production compared with that in unstimulated (control) cells. (B) LPS (100 ng/mL)-stimulated cells incubated with and without VIP (10^–8 M). TNF- levels were measured by ELISA and compared with unstimulated (control) cells or cells stimulated with phorbol myristate acetate (positive control). Data are presented as means ± SD (n = 3). *P < 0.05. Similar data were obtained from 3 separate experiments.