Depression of humoral immunity to sheep erythrocytes in vitro by Friend virus leukemic spleen cells: induction of resistance by statolon

Abstract

The in vitro antibody plaque-forming cell (PFC) response of normal spleen cells exposed to sheep erythrocytes in Marbrook chambers was depressed by the addition of Friend virus (FV) leukemic spleen cells. Fewer than 10-5 leukemic cells inhibited the PFC response of 10-7 normal cells. This immunodepression could not be produced with sonicated, irradiated, or mitomycin C-treated leukemic cells or with cellfree FV. It could be blocked by FV immune serum but was unaffected by high titers of purified interferon. Interferon did not inhibit the immune response of normal spleen cells to sheep erythrocytes. Spleen cells from mice treated with statolon or chlorite-oxidized oxyamylose statolon but not Newcastle disease virus or poly rI:poly rC were resistant to immunodepression in vitro by FV leukemic spleen cells. The unique ability of statolon to prevent immunodepression by leukemic spleen cells may be the basis of its FV leukemo-suppressive activity in vivo.