Tolerance to dinitrofluorobenzene (DNFB) contact sensitivity (DNFB CS) appeared in C3H/HeN mice within 2 days after application of DNFB on Langerhans cell-deficient tail skin A single painting on tail skin led to complete prevention of DNFB CS for at least 14 days Spleen ceils from tolerant mice could transfer the suppression to syngeneic recipient?., while the cells treated in vitro with anti-Thy 1 2 lost their suppressive activities completely From these facts, this tolerance might be due to active suppression caused by suppressor T cells These suppressor T cells were antigen-specific, because recipients exhibited normal CS to picryl chloride Furthermore, the suppressor T cells were demonstrated to be afferent blockers in nature and their precursors were sensitive to cyclophosphamide Therefore, the suppressor T cells induced by DNFB percutaneously administered through epidermal Langerhans cell-deficient region were thought to be generated in the same or in a very similar suppressor pathway as the intraveneously administered dimtrobenzene sulfonate (DNBSO₃), a sofuble reactive dinitrophenyl congener