Participation of suppressor-inducer cells in the suppression of adjuvant arthritis by transfer of spleen cells expanded by T cell growth factor.

We attempted to elucidate the mechanism of action of T cell growth factor (TCGF)-expanded cells after stimulation with concanavalin A (Con A), a process which reduces the severity of adjuvant arthritis (AA), as seen in transferred syngeneic rats. TCGF-expanded cells were fractionated by Percoll density gradient or by the panning method, before the transfer. Transfer of cells with a density of between 1070 and 1079 suppressed AA most effectively, compared with other fractions with a density of less than 1070. A large number of the cells with density 1070-1079 were of the W3/25 phenotype. The transfer of W3/25 positive cells obtained by the panning method from TCGF-expanded cells reduced AA but not W3/25 negative cells. The suppressor function of TCGF-expanded cells was examined in an assay system in vitro. The addition of Con A-stimulated cells to the assay culture (but not expanded with TCGF), suppressed both the proliferation of spleen cells stimulated with Con A and the IgG production stimulated with lipopolysaccharide. The addition of TCGF-expanded cells to the assay culture had no effect on these responses. Thus, the W3/25 cells in the TCGF-expanded cells seem to function as suppressor-inducer cells, affect the presuppressor cells of the recipient rat and differentiate to suppressor effector cells.