Inhibition of lymphycyte reactivity in vitro by autologous polymorphonuclear cells (PMN).

The influence of autologous polymorphonuclear cells (PMN) on lymphocyte reactivity was investigated by monitoring the uptake of tritiated thymidine by unstimulated, phytohemagglutinin (PHA)-stimulated, and fetuin-stimulated lymphocytes in vitro. Addition of PMN at PMN-to-lymphocyte ratios (P:L) of 0.5 to 2.0 progressively inhibited lymphocyte reactivity. Soluble extracts, obtained by sonication and ultracentrifugation (100,000g for 90 min) of PMN, also inhibited lymphocytes. The PMN-derived inhibitor(s) is noncytotoxic, heat labile (56 °C for 60 min), resistant to freeze-thawing (20 cycles), and appears to be nondialyzable. Inhibition was more marked when the factor was added at the initiation of lymphocyte cultures than when added with the tritiated thymidine 24 hr prior to cell harvest. Thus thymidine released by PMN which diluted the radiolabeled nucleotide and degradation of the tritiated thymidine did not explain these results. Lymphocytes incubated for 3 days in the medium containing the inhibitor reacted normally to PHA following washing, indicating that inhibition was reversible. These results suggest that a PMN-derived lymphocyte inhibitor(s) may modulate lymphocyte-mediated immune reactivity.