Transmission of dengue virus-induced suppressor signal from macrophage to lymphocyte occurs by cell contact.

We have observed that live macrophages play an obligatory role in transmission of dengue type 2 virus (DV)-induced suppressor signal to a subpopulation of T lymphocytes. The present study was undertaken to resolve whether transmission of the suppressor signal is mediated by a soluble factor or by direct cell-to-cell contact. It was observed that the suppressor factor (SF) remains adsorbed on the surface of macrophages and can be retrieved from them completely by DV-stimulated spleen cells kept in contact with them. Suppression of DV-specific IgM plaque-forming cells (PFC) in spleen-cell cultures does not occur when SF-adsorbed macrophages are separated from them by cell-impermeable membranes. Culture fluid of SF-adsorbed macrophages have no suppressor activity. The suppression of PFC occurs only when SF-adsorbed macrophages remain in contact with DV-stimulated spleen-cell cultures. Thus transmission of suppressor signal from SF-adsorbed macrophages to lymphocytes occurs only by physical contact of the plasma membranes of the interacting cells.