ABSTRACT
While the presence of a lymphocytic parenchymal infiltrate is characteristic of several lung diseases, the mechanisms responsible for the focal accumulation of lymphocytes within the lungs remain unclear. Since alveolar macrophages secrete several substances that affect lymphocyte function, we examined supernatants of stimulated, cultured guinea pig alveolar macrophages for their ability to alter lymphocyte motility. Guinea pigs were immunized by footpad injection of ovalbumin (OVA) emulsified in complete Freund's adjuvant. Fourteen days later, alveolar macrophages were obtained by bronchial lavage or teasing the lung parenchyma, enriched by adherence to plastic, and incubated for 3 and 24 hours in culture medium alone or medium containing either latex beads, OVA, or human serum albumin (HSA). Conditioned medium was harvested and assayed for chemoattractant activity against rat splenic lymphocytes in modified Boyden chambers. Regardless of stimulus, there was no evidence of enhanced lymphocyte motility above control values in supernatants harvested at 3 hours. At 24 hours, alveolar macrophages from OVA-sensitized guinea pigs stimulated with latex or OVA generated significant amounts of lymphocyte migration stimulating activity (LCA) (250 +/- 25 and 247 +/- 24 percent of control migration, respectively) compared to cells incubated in medium alone or with HSA (162 +/- 23 and 147 +/- 14 percent, respectively). Antigen recognition appears to be related to the presence of cytophilic anti-OVA antibody on the surfaces of alveolar macrophages of sensitized guinea pigs. LCA is resistant to neuraminidase, chymotrypsin, and heating to 56 degrees C, and was chemokinetic for T-lymphocytes. it elutes from Sephadex G-100 in two regions: one at approximately 67,000 d, and a second at approximately 15,000 d. These studies indicate that following systemic immunization, the guinea pig alveolar macrophage can react to specific antigen or phagocytosis of inert particulates by secreting a chemokinetic factor for T-lymphocytes, and may play a role in the pathogenesis of some types of antigen-induced lung disease.