Phospholipid mediator of platelet aggregation, inflammation, and anaphylaxis. Produced in response to specific stimuli by a variety of cell types, including neutrophils, basophils, platelets, and endothelial cells. Several molecular species of PAF have been identified which vary in the length of the O-alkyl side chain. In vitro identification of a soluble platelet activating factor produced by antigen stimulated leukocytes: P. M. Henson, J. Exp. Med. 131, 287 (1970). Isoln from rabbit basophils, characterization of PAF response and potential role in immune complex disease: J. Benveniste et al., ibid. 136, 1356 (1972). Isoln from human leukocytes: J. Benveniste, Nature 249, 581 (1974). Release of PAF in vivo during anaphylaxis: R. N. Pinckard et al., J. Immunol. 123, 1847 (1979). Structural study: J. Benveniste et al., Nature 269, 170 (1977); and synthetic approaches: J. Benveniste et al., C. R. Seances Acad. Sci. Ser. D 289, 1037 (1979); C. A. Demopoulos et al., J. Biol. Chem. 254, 9355 (1979). Identity with APRL and antihypertensive activity: M. L. Blank et al., Biochem. Biophys. Res. Commun. 90, 1194 (1979). Structures of 1-O-octadecyl- and 1-O-hexadecyl-PAF, two of the predominant molecular forms: D. J. Hanahan et al., ibid. 255, 5514 (1980). Total synthesis of 1-O-octadecyl-PAF: J. Godfroid et al., FEBS Lett. 116, 161 (1980). Enantiomeric synthesis of C16- and C18-PAF: M. Ohno et al., Chem. Pharm. Bull. 33, 572 (1985). Molecular heterogeneity of naturally occurring PAF: R. N. Pinckard et al., Biochem. Biophys. Res. Commun. 122, 325 (1984); H. W. Mueller et al., J. Biol. Chem. 259, 14554 (1984). Ulcerogenic effects: A.-C. Rosam et al., Nature 319, 54 (1986). Effects on human pulmonary and cardiovascular function: F. M. Cuss et al., Lancet 2, 189 (1986). Review of isoln and analytical methods: D. J. Hanahan, S. T. Weintraub, Methods Biochem. Anal. 31, 195-219 (1985); of chemical and biochemical characteristics: D. J. Hanahan, R. Kumar, Prog. Lipid Res. 26, 1-28 (1987). Reviews of biosynthesis, biological activities and PAF antagonists: P. Braquet et al., Pharmacol. Rev. 39, 97-145 (1987); P. J. Barnes et al., J. Allergy Clin. Immunol. 81, 919-934 (1988). Books: Platelet-Activating Factor and Related Lipid Mediators, F. Snyder, Ed. (Plenum Press, New York, 1987) 471 pp; Prog. Biochem. Pharmacol. 22 entitled “Biologically Active Ether Lipids” by P. Braquet et al., Eds. (Karger, Basel, 1988).