THE MOUSE MACROPHAGE ACTIVATION-ASSOCIATED MARKER PROTEIN, P71 73, ISAN INDUCIBLE PROSTAGLANDIN ENDOPEROXIDE SYNTHASE (CYCLOOXYGENASE)/

The inducible protein p71/73 marks the response of mouse macrophages t o one of several stimuli (e.g., bacterial lipopolysaccharide or poly I :C) that trigger the expression of cytolytic activity when these cells have previously been primed for tumor cell killing by interferon-gamm a (IFN-gamma). The results reported here identify this marker protein as the inducible prostaglandin endoperoxide synthase (PES), TIS10/PES- 2. Identification was based on four findings: (1) p71/73, like the TIS 10/PES-2 protein, was associated with cellular membranes; (2) the sequ ence of amino acids in the NH2 terminus of both p71 and p73 was 96% id entical to the predicted NH2-terminal sequence of the TIS10/PES-2 prot ein; (3) a polyclonal antiscrum raised against the COOH-terminal regio n of the TIS10/PES-2 gene product recognized p71/73 in immunoblots; an d (4) dexamethasone, which blocks induction of TIS10/PES-2 expression, inhibited the induction of both p71/73 synthesis and tumoricidal acti vity in macrophage. Several regulatory roles for this protein in the a ctivation process are possible.