Investigation of the immunocompetent cells that bind early pregnancy factor and preliminary studies of the early pregnancy factor target molecule

Abstract

Summary Early pregnancy factor (EPF) is a secreted protein with immunosuppressive and growth factor properties. It has been shown to suppress the delayed-type hypersensitivity response in mice as well as acute and chronic forms of experimental autoimmune encephalomyelitis in rats and mice, respectively. In previous studies, we have demonstrated that EPF binds to a population of lymphocytes and we hypothesized that it mediates its suppressive effects by binding to CD4 + T cells. In the present study, we isolated monocytes and subpopulations of lymphocytes and labelled them with fluoresceinated EPF in order to determine which populations bind EPF. We demonstrated that EPF binds specifically to CD4 + , CD8 + , CD14 + (monocytes) and CD56 + NK cells but not to CD19 + B cells. The identity of the molecule(s) on the cell surface that is targeted by EPF is unknown, but as EPF is an extracellular homologue of the intracellular protein chaperonin 10 (Cpn10), we examined the possibility that the EPF receptor is a membrane-associated form of chaperonin 60 (Cpn60), the functional associate of Cpn10 within the cell. The EPF target molecule on lymphocytes was visualized by chemical cross-linking of exogenous iodinated Cpn10 to cells and probed with anti-Cpn60. The effect of anti-Cpn60 on activity in the EPF bioassay, the rosette inhibition test, was also examined. In both instances, no specific interaction of this antibody and the putative receptor was observed. It was concluded that the cell surface molecule targeted by EPF is unlikely to be a homologue of Cpn60.

Heat Shock Protein 10 Inhibits Lipopolysaccharide-induced Inflammatory Mediator Production

“…This line of reasoning might lead one to speculate that the physiological role of circulating Hsp10 during early pregnancy (38) may be to remove the Hsp60 danger signal (15) that has arisen from pregnancy (73,74) rather than from pathogen-induced tissue damage. We are currently in the process of seeking formal proof of Hsp10 binding to extracellular Hsp60, as it remains possible that Hsp10 binds to an alternative receptor (75) and that Hsp10 and anti-Hsp60 exert similar suppressive (but non-additive) effects on TLR4 signaling (Fig. 7) but use distinct pathways.…”

Heat shock protein 10 and signal transduction: a “capsula eburnea” of carcinogenesis?

“…In a human model, it has been shown that EPF binds specifically to CD4 ϩ , CD8 ϩ , CD14 ϩ (monocytes), and CD56 ϩ natural killer cells, and its suppressive effects are driven by inhibition of CD4 ϩ T cell activity (Athanasas-Platsis et al 2004). At the same time, EPF is known to stimulate the proliferation of many different cells .…”

Recombinant EPF/chaperonin 10 promotes the survival of O4-positive pro-oligodendrocytes prepared from neonatal rat brain

“…It is known that TLR 4 is needed for lps induced injury of oligodendrocytes (Lehnardt et al 2002), and it may be that cpn 10 supports the survival of oligodendrocyte precursors in vitro through a mechanism involving toll-like receptors. However, there is also some evidence that there may be a specific receptor for EPF/cpn 10 (Athanasas- Platsis et al 2004), which provides another possible mode of action. The suggestion of an extracellular role for heat-shock proteins (hsps) such as cpn 10 is not unprecedented.…”