Addition of gamma-irradiated
reticulum cell sarcoma (RCS) cells causes suppression of the antibody response to trinitrophenyl (TNP)-
keyhole limpet hemocyanin (KLH)-primed syngeneic SJL spleen cells to
TNP-polyacrylamide (PAA) in vitro. The response of anti-brain
antigen (BAT) + C-treated spleen cells is not suppressed by gamma-RCS, but is suppressed by cells from 48-hr SJL lymph node or thymus + gamma-RCS cultures. Addition of as few as 2.5 x 10(5) cultured (anti-I-A + C treated to remove gamma-RCS) cells causes significant inhibition of the responses of both syngeneic and allogeneic spleen cells. Treatment of gamma-RCS-induced suppressor cells with anti-BAT + C reduces their suppressive activity. In contrast to the cells, supernatants (SN) from (lymph node (LN) + gamma-RCS) cultures greatly enhance, in an
antigen-dependent fashion, the responses of untreated or anti-BAT + C-treated
Sephadex G10-passed spleen cells to TNP-PAA. TNP-SIII
polysaccharide, or
TNP-Ficoll, but not as much to
TNP-KLH. Addition of SN as late as Day 3 of culture still causes about half as much enhancement as leaving SN in throughout the culture period, but it has no effect if left with the spleen cells for only the first day of culture. SN contains high levels of
IL-2 and IFN-gamma; absorption with cells from an IL-2-dependent cytotoxic T-cell line removes the enhancing activity, while treatment with pH 2 to remove the IFN-gamma has no effect. SN from an IL-2-producing T-cell line (LBRM-33) has a similar effect on antibody production to TI
antigens as does SN of (LN + gamma-RCS). The results suggest a marked dependency of PFC responses to TI
antigen on
IL-2 in all strains examined, including SJL, LAF1, DBA/2Ha, and CBA/N, probably through a direct activation of B cells. The findings also suggest that suppressor T cells, induced by gamma-RCS in syngeneic lymphoid cells, absorb the
IL-2 needed for responses to TI
antigens in vitro.