Rickettsial effects on leukotriene and prostaglandin secretion by mouse polymorphonuclear leukocytes

Typhus rickettsiae were incubated with mouse exudative polymorphonuclear leukocytes (PMN), and supernatants were examined for leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) secretion by radioimmunoassay. PMN incubated with native rickettsiae secreted significantly more LTB4 and PGE2 than did those incubated with buffer alone. Autacoid secretion was dependent on both the time of PMN incubation with rickettsiae and the number of rickettsiae present in the incubation suspension. Rickettsial stimulation of LTB4 secretion was associated with rickettsial hemolytic activity; treatments which inactivated the rickettsial hemolysin abolished the ability of rickettsiae to stimulate PMN LTB4 secretion. Trifluoperazine, which did not alter the rate of phagocytosis of rickettsiae by PMN, stimulated rickettsial effects on secretion of both LTB4 and PGE2 but inhibited the PMN LTB4 response to A23187. This suggested that the PMN response to rickettsiae and to the calcium ionophore involved differing mechanisms of activation. Finally, rabbit antirickettsial antiserum, which inhibited rickettsial hemolysis and was opsonic, did not block the effects of rickettsiae on PMN LTB4 secretion.