Fig. 1.

Dose–response analysis of heat-inactivated bacteria, LPS, PPS and CWPS on cytokine production. Whole blood from a healthy, blood group O subject was incubated with increasing amounts of heat-inactivated bacteria, LPS, PPS or CWPS for 6 h to ascertain the lowest concentration of each antigen to elicit a cytokine response. Each datum point represents the mean of duplicate determinations. Negative controls (unstimulated blood) are not shown because in all cases the cytokine level was <0·03 ng/ml.