Blocking antigen-antibody complexes on the T-lymphocyte activation during in vitro incubation before adoptive transfer.

Following appropriate immunization of mice with CGG or DNP-CGG spleen cells release antigen upon incubation in vitro. The release can be detected either by 'self-stimulation' of the primed cell population, so that upon adoptive transfer antibodies to CGG and DNP are produced without need for further administration of antigen, or by stimulation of indicator (primed) cells. Boosting mice with antigen in saline following initial immunization with antigen in adjuvant proves the most effective method of loading spleen cells with antigen. A small fraction (10- minus 4- minus 10- minus 5) of the antigen used for boost is retained. The antigen appears to be held on the cell surfaces in the form of antigen-antibody complexes, for it is retained on the cells for up to 13 weeks in the presence of circulating antibody, during which time its capacity to self-stimulate can be inhibited by host serum in vitro. Activated thymus cells take up detectable amounts of antigen-antibody complexes. Complexes obtained by immunization with antigen in adjuvant can be inactivated by trypsinizing spleen cells. Trypsinization of separated T and B cells reveals detectable amounts of complex on the T cells, Complexes detected on T cells in this way are believed to be equivalent to the blocking complexes operative in transplantation and tumour immunity.