Differentiation stimuli induce receptors for plasma fibronectin on the human myelomonocytic cell line HL-60

Abstract

Plasma fibronectin (Fn) induces phagocytosis of C3b-opsonized sheep erythrocytes (EC3b) by human peripheral blood monocytes. However, Fn does not induce erythrophagocytosis of EC3b by human polymorphonuclear leukocytes (PMN), unless the PMN have been exposed to C5a or N-formyl- methionyl-leucyl-phenylalanine. Because of this difference, it is of great interest to examine Fn binding to cells that possess the capacity to differentiate into either granulocytes or monocytes. Hence, we have examined the consequences of Fn binding to the human myelomonocytic cell line, HL-60, both before and after in vitro differentiation of the HL-60, along a monocytoid or a granulocytoid pathway. Fn receptors were not found on undifferentiated HL-60, but several differentiating agents promoted the HL-60 binding of Fn-coated microspheres (Fn-ms). The peak of Fn-ms binding occurred four to five days after the induction of differentiation with dimethylsulfoxide (DMSO), and two days after induction by PMA. In addition, cells that differentiated along either the monocytoid or the granulocytoid pathway showed a marked increase in the phagocytosis of both IgG-coated erythrocytes (EA) and EC3b when they were exposed to Fn. Comparison of the effects of anti-Fn monoclonals on the binding of Fn-ms to the monocytes, PMN, and HL-60 showed that the same monoclonals block Fn-ms-binding and Fn-induced EC3b phagocytosis by all three cell types. Two monoclonal antibodies, M1/70 and A6F10, directed against membrane antigens on PMN and monocytes, inhibited Fn-ms binding. Both also blocked Fn-induced EC3b ingestion by these cells. However, neither antibody blocked Fn-ms binding or EC3b ingestion by differentiated HL-60. We conclude that differentiated HL-60 cells express functionally active Fn receptors, similar to monocytes and activated PMN, which, nonetheless, differ from normal cells in their association with the antigens recognized by M1/70 and A6F10.

Fibronectin receptors of phagocytes. Characterization of the Arg-Gly-Asp binding proteins of human monocytes and polymorphonuclear leukocytes.

“…is consistent with the incompletely disulfide-bonded molecules in the ,# chain of the Fn receptor that binds to peptide-Sepharose . A6F10 blocks monocyte binding to Fn-coated surfaces (34), and the binding of Fn-coated microspheres to monocytes and PMNs (8), which suggests that the phagocyte receptor molecules without intrachain disulfide bonds exist and retain ligand specificity in the cell membrane as well as in detergent extracts of monocytes and PMN. An mAb that binds to both gpIIb/IIIa and to PMN and monocytes has been reported to inhibit the binding of Fn-coated particles to these cells (35).…”

Protein kinase C and a calcium-independent phospholipase are required for IgG-mediated phagocytosis by Mono-Mac-6 cells

“…The cells were harvested at a density of 0.5 to 1.0 ϫ 10 6 /mL. Human monocytes were purified from lymphoplatelet preparations (Albany Medical Center apheresis unit) by countercurrent elutriation as previously described [12]. These preparations were Ͼ90% pure monocytes as determined by forward and side light scattering.…”

“…The FITC-loaded SRBC were washed with ice-cold VBS five to seven times to remove excess free FITC-dextran. FITC-SRBC were coated with IgG (EIgG) as previously described [12].…”

Molecular cloning of a murine fibronectin receptor and its expression during inflammation. Expression of VLA-5 is increased in activated peritoneal macrophages in a manner discordant from major histocompatibility complex class II.

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Macrophages secrete fibronectin (Fn)' (1-3), bind Fn (3-5), and have been reported to migrate in response to Fn fragments (6). In addition, the interaction of human macrophages with Fn provides a second signal that leads to enhanced complement and Fc receptor-mediated phagocytosis by these cells (7)(8)(9)(10)(11)(12)(13)(14) . The structure ofthe Fn receptor, or receptors, responsible for both adherence to Fn and Fn-mediated phagocytosis enhancement in macrophages is not completely understood .

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