Characterization of inflammatory mediator release from purified human lung mast cells.

The release of inflammatory mediators (histamine, PGD2, TxB2, and LTC4) from purified human lung mast cells was characterized by kinetic and anti-IgE dose-response parameters. The relative rate of mediator release was histamine greater than PGD2 = TxB2 greater than LTC4, with one half maximal release occurring at approximately 2, 5, and 10 min, respectively. In 2 experiments, stimulation with anti-IgE caused significant quantities of platelet-activating factor (PAF) to appear rapidly (2 min) in the cell pellet; cell-associated PAF declined to low levels by 45 min. The optimal concentration of anti-IgE for the release of the arachidonate cyclooxygenase metabolites PGD2 and TxB2 (0.3 microgram/ml) was 10- to 30-fold less than that required for the release of histamine and LTC4 (3 to 10 micrograms/ml), suggesting that these release processes may have differential IgE Fc receptor cross-linking requirements. At optimal histamine release, the magnitude of the release of each arachidonate metabolite was found to correspond to the magnitude of histamine release, however, suggesting that the 2 processes are linked either in series or in parallel.