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 > PGD₂ = TxB₂ > 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 μg/ml) was 10- to 30-fold less than that required for the release of histamine and LTC₄ (3 to 10 μg/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.