The Transfer of Immunological Tolerance With Tolerant Lymphocytes

Summary Immunological tolerance of sheep erythrocytes has been transferred to normally reactive rats. Transfer could be effected by parabiosis of tolerant and normal rats or by the transfer of cell suspensions from a tolerant donor to a normal recipient. While thoracic duct lymphocytes and spleen cells from tolerant donors were highly effective in transferring tolerance, bone marrow cells were completely lacking in this capacity. Preliminary lymphocyte depletion of a prospective normal transferee assisted, but was not mandatory for, subsequent establishment of the tolerant state. It is suggested that tolerance of sheep erythrocytes is characterized by the presence of repressor cells.