Release of a chemotactic monokine upon treatment with lymphocyte supernatants

Macrophages produced and/or released a chemoattractant(s) for neutrophils after having been treated for 2 hr with soluble products from two lymphoma cell lines. Culture supernatants of the EL-4 and Yac-1 cell lines, but not sarcoma l, Bc100, or the macrophagelike cell line P388d1, triggered the release of the chemoattractant. The macrophage-derived chemoattractant (MDC) was detectable within 2 hr following triggering and culture supernatants had maximal activity by 48 hr. The triggering of the macrophages to release the chemoattractant and the activity of the chemoattractant was not dependent upon any component of fetal bovine serum. Activation of complement was also not involved, since activated serum did not competitively inhibit the chemotactic activity of the macrophage-derived chemoattractant. The chemoattractant was macromolecular, stable to heating at 90 degrees C for 15 min, sensitive to pronase and chymotrypsin, and was affected by treatment with low pH.