Induction of autoantibody-producing cells after the coculture of haptenated and normal human mononuclear leukocytes

The coculture of normal human peripheral blood mononuclear leukocytes (PBL) and autologous mononuclear leukocytes coupled to the trinitrophenyl (TNP) hapten (TNP-PBL) was found to induce a polyclonal activation of antibody-producing cells. The polyclonal activation of antibody-producing cells was demonstrated by detecting the induction of cells producing antibody to sheep red blood cells using a complement-dependent, direct, hemolytic plaque-forming cell (PFC) assay. A ratio of four normal to one haptenated mononuclear leukocyte was found to be optimal for inducing the polyclonal activation of antibody-producing cell in these cultures. The plaque-forming cells assay in these experiments utilized monolayers of indicator red cells. Further evidence for the polyclonal induction of antibody-producing cells by TNP-PBL was provided by demonstrating PFC on monolayers of not only sheep red blood cells, but also autologous human red cells, bromelain-treated autologous red cells, TNP-coupled human and sheep red cells, and human autologous red cells coupled to human heat-aggregated IgG with chromic chloride. Thus cells secreting antibody to TNP, human red cells, and human IgG were induced. Anti-IgG and anti-human red cell-producing cells were first detected on Day 2 of culture and were still present on Day 9. Mononuclear leukocytes altered by chemical haptenation polyclonally stimulate normal mononuclear leukocytes to become antibody-producing cells. This polyclonal stimulation of antibody-producing cells includes cells producing antibodies to human IgG and human autologous red blood cells suggesting that autoantibody-producing cells are induced.