Activation of alveolar macrophages exposed to lavage-procured immunoglobulin G obtained from normal rabbit lungs.

Pulmonary washings from rabbits were freed of cells and added to the monolayers of homologous alveolar macrophages (AM). At 1 h after incubation with the pulmonary washings, many more cells adhered to glass, spread out, and showed enhanced Nitro Blue Tetrazolium reduction. The maximal effect of the pulmonary washings on AM activation was obtained 12 h after incubation. The AM activated by the pulmonary washings showed a higher capacity to inhibit the growth of intracellular BCG, and that capacity was correlated with the intensity of Nitro Blue Tetrazolium reduction by the AM. Gel filtration of the pulmonary washings through Sepharose 4B yielded five fractions. The factor that activated the AM functions was in fraction 4. When the immunoglobulin G in the fraction was removed by an immunoadsorbent column, AM activity was abolished. The effect of the immunoglobulin G was dose dependent, and minimal responses to 10(6) cells per ml were obtained at a protein concentration of 20 mug/ml. Lymphokines had no effect on AM activation with respect to the morphological alterations and Nitro Blue Tetrazolium reduction during the 24-h observation time. In summary, AM from normal rabbits were soon activated markedly by lavage-procured immunoglobulin G, but not by lymphokines.