Fc gamma 2b receptor-mediated prostaglandin synthesis by a murine macrophage cell line (P388D1).

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Abstract
The nature of signals transmitted by two types of Fc gamma receptors (one specific for IgG2b and the other for IgG2a) present on the surface of a murine macrophage cell line (P388D1) was investigated. Specific binding of IgG2b (presented as EA2b) to cell surface Fc gamma 2br triggered the release of 3H-arachidonic acid and 3H-prostaglandins (PG) from P388D1 cells that were prelabeled with 3H-arachidonate. The release of 3H-arachidonic acid, which increased in a dose-dependent manner, was enhanced by exogenous Ca++ (1.25 mM) and was completely blocked by ethylenediaminetetraacetate (EDTA) (4 mM) or a phospholipase A2 inhibitor, p-bromophenacylbromide (7 microgram/ml). A cyclooxygenase inhibitor, indomethacin (9 microgram/ml), reduced the 3H-arachidonic acid release and completely blocked the conversion of arachidonate into PG. Cytochalasin D (1 microgram/ml), which inhibited the phagocytosis of immune complexes by 90% of P388D1 cells, did not affect the Fc gamma 2bR-triggered release of arachidonic acid. Specific binding of IgG2a (presented as EA2a) to cell surface Fc gamma 2aR did not trigger the release of either 3H-arachidonic acid or 3H-PG from P388D1 cells. Our data demonstrate a signal for the activation of the arachidonic acid metabolic cascade is transmitted by Fc gamma 2bR, but not by Fc gamma 2aR, on the surface of P388D1 cells, probably through the initial activation of the phospholipase A2 activity associated with Fc gamma 2bR.