Induction of Suppressor T Cells by Anti-Globoside Antibodies in Cancer Sera

T cells treated with cancer sera frequently suppressed immunoglobulinproduction by autologous lymphocytes stimulated with pokeweedmitogen. Sera from healthy individuals did not induce suppressoractivity. This suppression is not caused by T_G cells (T cellsbearing receptors for the Fc portion of immunoglobulin G IgG])interacting with immune complexes, because we used T cells depletedof T_G cells. The suppressor-inducing factors were separatedinto an IgG-containing fraction and a fraction with a smallermolecular weight. IgG fractions from all sera that were positivefor anti-globoside antibody induced suppressor T cells, andelimination of the anti-globoside antibody from these IgG fractionsreduced the ability to induce suppressor T cells. T cells treatedwith rabbit anti-globoside antiserum also activated suppressorT cells. These observations indicate that the antibodies directedto the globoside antigen on suppressor T cells stimulate thesuppressor T cells, and that anti-globoside antibody in cancersera may play a role in causing immunodeficiency in cancer patients.