Smooth muscle contraction and release of histamine and slow-reacting substance of anaphylaxis in pulmonary tissues isolated from guinea pigs passively sensitized with IgG or IgE antibodies

In previous studies, we have provided evidence that different Fc receptors mediate antigen-induced pulmonary smooth muscle contractile responses after passive sensitization of guinea pigs with IgG₁ or IgE antibodies. In this study, we examined the relationship between contraction and release of histamine and slow-reacting substance of anaphylaxis (leukotrienes) in superfused trachea and parenchymal strips as well as mediator release from minced lung fragments after passive sensitization of guinea pigs with IgG₁ or IgE antibodies. Guinea pigs were immunized to produce either IgG₁ or IgG₁ and IgE using oxazolone-guinea-pig albumin or oxazolone-Ascaris plus cyclophosphamide, respectively. The contaminating IgG₁ in the IgE-rich serum was removed by passage over a protein A-Sepharose column. Normal guinea pigs were passively sensitized intraperitoneally or intravenously with injections of either IgG₁ or IgE 1 or 2 days before in vitro studies. Superfused tissues were challenged with 10^-1 mg/ml antigen (oxazolone-human serum albumin conjugate), and contractions and histamine and leukotriene release were monitored at discrete time intervals thereafter. At equivalent levels of contraction, substantially more histamine and leukotrienes were released from tissues taken from IgG₁-sensitized animals. The amounts of histamine released from lung parenchymal strips and trachea in the IgE-sensitized state were approximately 5 and 38%, respectively, of those released from corresponding tissues in the IgG₁-sensitized state. The leukotriene release from tissues isolated from IgE-sensitized animals was less than 4% of that released from tissues in the IgG₁-sensitized state. Similar differences in mediator release were seen in comparable studies on minced lung fragments. In all cases, the ratio of leukotriene bioactivity to histamine was larger in parenchyma than in trachea. In a study comparing active versus passive sensitization, contraction and mediator release were not substantially different. A more rapid rise to peak contraction and histamine release were seen in the actively sensitized state. These data demonstrate quantitative differences in histamine and leukotriene release mediated by IgG₁ and IgE antibodies in pulmonary tissues of the guinea pig. This may indicate that qualitative differences exist in events leading to antigen-induced airway smooth muscle contraction mediated by the two antibodies.