Production of a lymphocyte proliferation potentiating factor by purified polymorphonuclear leucocytes from mice and rabbits.

Highly pure polymorphonuclear leucocytes (PMN) were prepared from peritoneal exudate cells which were induced by an i.p. injection of casein into C3H mice and rabbits. The PMN were tested for the production of a lymphocyte proliferation potentiating factor with various stimulations in vitro. In both animal species, the purified PMN from the inflammatory site 3 hr after injection (3-hr PMN) produced the factor upon stimulation with kaolin, while the purified PMN from the lesion 24 hr after injection (24-hr PMN) did not. The 3-hr PMN produced the potentiating factor during a relatively earlier period after in vitro stimulation with kaolin. Protein synthesis inhibitors did not inhibit the factor production, suggesting the release of a preformed factor from 3-hr PMN. The effect of kaolin did not appear to be simply due to its cytotoxicity, because the release was dependent on the metabolism of 3-hr PMN and not parallel with 51Cr-release from the PMN. The factor produced by mouse PMN had an MW of about 15,000-25,000; it consisted of two isoelectrophoretically distinct factors, i.e. pI 9.4 and 5.4. The rabbit PMN factor was slightly smaller (MW ranging between 10,000 and 20,000) than the mouse PMN factor and was composed of three pI species, i.e. 7.2, 5.4, and 4.5.