DISTINCT PATTERNS OF DIFFERENTIATION-INDUCED IN THE MONOCYTIC CELL-LINE MONO-MAC-6

The human Mono Mac 6 cell line exhibits many characteristics of mature blood monocytes including expression of the CD14 molecule and production of cytokines, such as interleukin-1 (IL-I), IL-6, and tumor necrosis factor. To determine whether these cells can be further differentiated, we treated the cells for up to 3 days with either prostaglandin E(2) (PGE(2); 10(-5) or 10(-6) M), lipopolysaccharide (LPS; 10-20 ng/ml), or tetradecanoylphorbol-13-acetate (TPA; 10-50 ng/ml). All three reagents reduced proliferation and expression of the early myelomonocytic antigen CD33, and all increased phagocytosis of staphylococci and constitutive expression of mRNA for the macrophage colony-stimulating factor (M-CSP) receptor. By contrast, with respect to CD23 (Fc epsilon RII) expression, CD14 expression, and production of O-2(-), the three reagents induced distinct responses. Expression of CD23 (Fc epsilon RII) on Mono Mac 6 cells (36%) was not increased by LPS and TPA but was increased by PGE(2) treatment to 48%, with a 50% increase of fluorescence intensity. The CD14 antibody My4 stained more than 75% of untreated Mono Mac 6 cells with a specific mean fluorescence intensity of 87.5 channels. This staining was increased more than twofold by both PGE(2) and LPS. Staining with the CD14 antibody UCHM1 (6%) was increased to 43% by PGE(2) and to 43% by LPS. This increase in CD14: cell surface expression was accompanied by a rise in soluble CD14: and enhancement of CD14 mRNA. By contrast, TPA treatment resulted in a twofold decrease of CD14 cell surface staining with no significant change in sCD14, while CD14 mRNA was transiently down-regulated. Secretion of O-2(-) (stimulated by TPA) was already detectable in untreated Mono Mac 6 cells (6.1 mmol/1.0(6) cells/30 min), and this response was enhanced 10-fold by pretreatment with LPS but not with PGE(2) or TPA. The kinetics of M-CSF receptor mRNA, CD14 expression, and O-2(-) production: revealed that these monocytic features started to increase at 6-24: h and were maximal at 2 days. These data suggest that the three reagents induce maturation of the Mono Mac 6 cells to different levels or into different branches of the monocyte system with the notable differences that PGE(2) enhances CD23 expression, LPS enhances O-2(-) secretion, and TPA down-regulates CD14.