The effect of various metals and PHA on TNF-α production of patients’ leukocytes. The effect of various metals (Ti 0.01 mM, Co 0.1 mM, Cr 0.1 mM, Ni 0.1 mM) and PHA (0.1 mg/ml) on TNF-α production of patients’ leukocytes in group 3 is shown. Cells were untreated or treated as indicated. (a) (unreactive) it is clearly demonstrated that metal challenge did not influence significantly the cytokine release before and after the surgery. (b) (reactive) however, Co, Cr, and Ti increased the TNF-α secretion significantly 3 months after surgery in 21% (8 patients) of group 3, which was increased up to 30% (12 patients) after 36 months, distinguishing a subgroup referred here as metal-sensitive patients in group 3. Positive control PHA increased TNF-α production significantly in each experiment. Columns represent means + SD, level of significance is shown, *p < 0.05. Note that Ni did not influence TNF-α secretion significantly.