Enhancement of in vitro immunoglobulin synthesis of human lymphocytes by lysosomal enzymes from polymorphonuclear leucocytes.

The effect of human peripheral blood polymorphonuclear leucocyte (PMN) extracts and PMN granule lysates on in vitro immunoglobulin (Ig) synthesis by autologous peripheral blood mononuclear cells was studied. The mononuclear cells were cultured for 3 days with or without autologous plasma. Newly synthesized Ig in the culture supernatants was measured using 14C-labelled amino acids by an immune coprecipitation method. Upon addition of a PMN extract to plasma-free cultures Ig synthesis was stimulated, the mean stimulation index (SI) of cultures from thirteen individuals, including nine normals, three patients with rheumatoid arthritis and one with psoriatic arthritis being 1-8 +/- 0-2 in comparison with control cultures (P less than 0-05). By contrast, in 10% fresh autologous plasma, PMN extracts yielded a mean SI of 0-9 +/- 0-1 indicating inactivation of the active extracts by plasma inhibitors. In experiments using PMN granule lysates containing high concentrations of beta-glucuronidase and cultured in RPMI 1640, the mean stimulation index was 3-2 +/- 0-7. Stimulation of Ig synthesis was also produced by trypsin. Stimulation of Ig synthesis was also produced by trypsin. Stimulating factors in PMN extracts were inhibited by Trasylol, a protease inhibitor. These results indicate that trypsin and proteolytic lysosomal enzymes in PMN increase Ig synthesis of human peripheral blood mononuclear cells. They suggest a possible new role of PMN in the potentiation of immunoglobulin synthesis.