Release of monocyte chemoattractants by polymorphonuclear leukocytes stimulated by their adhesion to stratum corneum opsonized via complement activation, measured with a human acute monocytic leukemic cell line, THP-1

Stratum corneum (SC) exposed to living tissues, induces inflammation characterized by the formation of mixed cell granulomas consisting of infiltrative polymorphonuclear leukocytes (PMNs) and monocytes/macrophages. In this study, to clarify the mechanism for the later monocyte accumulation in SC-induced granulomas, we evaluated monocyte chemotactic activity induced by PMNs treated with serum-opsonized SC by using a human acute monocytic leukemic cell line, THP-1. When the supernatant was obtained from a PMN suspension cultured with opsonized plantar SC, higher THP-1 chemotactic activity was detected as compared with that cultured with non-opsonized SC. Although some concentrations of the chemokines, MIP-1alpha and MIP-1beta, were detected in supernatants obtained from the PMN suspensions cultured with plantar SC than in the control suspensions of PMN alone, their production by PMN was not influenced by the opsonization procedure. In contrast, MCP-1 was found to be secreted from PMN suspensions constitutively, showing no correlation to this THP-1 chemotactic activity. Moreover, HPLC analysis of PMN suspensions indicated that factors with far higher molecular weight values than these chemokines are involved in the chemotaxis of THP-1 cells.