- Our previously established model of cy- tosolic phospholipase A2 (cPLA2)-deficient, differen- tiated PLB-985 cells (PLB-D cells) was used to de- termine the physiological role of cPLA2 in eicosanoid production. Parent PLB-985 (PLB) cells and PLB-D cells were differentiated toward the monocyte or granulocyte lineages using 5 10 8 M 1,25 dihy- droxyvitamin D3 or 1.25% dimethyl sulfoxide, re- spectively. Parent monocyte- or granulocyte-like PLB cells released prostaglandin E2 (PGE2) when stimulated by ionomycin, A23187, opsonized zymo- san, phorbol 12-myristate 13-acetate, or formyl- Met-Leu-Phe (fMLP), and monocyte- or granulocyte- like PLB-D cells did not release PGE2 with any of the agonists. The kinetics of cPLA2 translocation to nu- clear fractions in monocyte-like PLB cells stimulated with fMLP or ionomycin was in correlation with the kinetics of PGE2 production. Granulocyte-like PLB cells, but not granulocyte-like PLB-D cells, secreted leukotriene B4 (LTB4) after stimulation with ionomy- cin or A23187. Preincubation of monocyte-like par- ent PLB cells with 100 ng/ml lipopolysaccharide (LPS) for 16 h enhanced stimulated PGE2 produc- tion, which is in correlation with the increased levels of cPLA2 detected in these cells. LPS preincubation was less potent in increasing PGE2 and LTB4 secre- tion and did not affect cPLA2 expression in granulo- cyte-like PLB cells, which may be a result of their lower levels of surface LPS receptor expression. LPS had no effect on monocyte- or granulocyte-like PLB-D cells. The lack of eicosanoid formation in stimulated, differentiated cPLA2-deficient PLB cells indicates that cPLA2 contributes to stimulated eico- sanoid formation in monocyte- and granulocyte-like PLB cells. J. Leukoc. Biol. 76: 000-000; 2004.