Monoclonal nonspecific suppressor factor β inhibits interleukin‐4 secretion by a type‐2 helper T cell clone

Monoclonal nonspecific suppressor factor (MNSF) is a lymphokine product of a murine T cell hybridoma that inhibits the generation of lipopolysaccharide-induced immunoglobulin secreting cells in an antigen-nonspecific manner. Most recently, a cDNA clone encoding MNSFβ, a subunit of MNSF, was isolated and sequenced (Nakamura et al., Proc. Natl. Acad. Sci. USA 1995. 92: 3463). The MNSFβ cDNA encodes a 14.5-kDa ubiquitin-like protein showing several MNSF activities. We have previously observed that hybridoma-derived native MNSF can inhibit interleukin (IL)-4 secretion by bone marrow-derived mast cells. Therefore, we studied whether MNSFβ is also able to inhibit IL-4 secretion by the type-2 helper T cell clone D10. G4.1. MNSFβ inhibited both the IL-4 secretion and the proliferation of concanavalin A-activated D10 cells, although neither effect was complete.