A role for tumour necrosis factor-alpha in the human mixed lymphocyte culture reaction.

The possible role and influence of tumour necrosis factor-alpha (TNF-alpha) in the human mixed lymphocyte culture (MLC) reaction was investigated. Polyclonal rabbit sera to recombinant human-TNF-alpha (rhTNF-alpha) consistently inhibited the MLC, and this could be reversed by simultaneous addition of rhTNF-alpha to the culture medium. Under optimal cell culture conditions, the exogenous addition of 1000 U/mL of rh TNF-alpha had a variable but generally small enhancing effect on the MLC reaction. Additional studies have clearly highlighted the importance of MLC assay conditions in influencing the effect of exogenous rhTNF-alpha. Enhancement of the MLC reaction was only consistently observed under suboptimal cell culture conditions. While the present study clearly supports an important role for TNF in controlling the proliferative response in the human MLC reaction it also highlights the influence of in vitro tissue culture conditions in determining the effect of exogenous TNF-alpha in this assay.