IDENTIFICATION OF A SUBSTANCE, PREVIOUSLY SHOWN TO ENHANCE MITOGENESIS OF HUMAN-LYMPHOCYTES, AS THE ACETAMIDE OF P-AMINOBENZOIC ACID

We characterize here an arachidonic acid (AA)-derived metabolite previ ously found to have an adjuvant effect in phytohemagglutinin-induced m itogenesis of lymphocytes from mothers of newborn babies and from immu nodeficient infants. We named the metabolite 'compound 4' due to its p osition in a thin-layer chromatography system developed for isolation of eicosanoids. The compound was originally found to be produced by pe ripheral blood mononuclear leukocytes and the T cell leukemia line Jur cat after long-term (28-24 h) incubation with [1-C-14]AA. Compound 4 i s also produced by lymphocytes, monocytes, platelets, trombocytes, cul tured fibroblasts and various types of malignant cell lines. We purifi ed this metabolite by means of high pressure liquid chromatography wit h synchronous detection of radioactivity and measurement of ultraviole t-light absorption at 278 nm. Proton nuclear magnetic resonance spectr oscopy and mass spectrometry with electron impact techniques demonstra ted that compound 4 is not an eicosanoid, but is identical to p-acetam idobenzoic acid (PACBA). The cells synthezise PACBA from p-aminobenzoi c acid and a two-carbon residue from AA.