functional analysis of the defective t cell regulation of the antigenspecific pfc response in sle patients differentiation of suppressor precursor cells to suppressor effector cells the investigation described here is concerned with the t cell regulation of the antigenspecific antibody response which has been studied in patients suffering from systemic lupus erythematosus sle apart from the fact that t helper cell activity was found to be less efficient it appeared that the peripheral blood leucocytes pbl of patients in an active stage of the disease did not contain the suppressor precursor cells which functions as the target cell for the inductive signal of t mu suppressor inducer cells the absence of the suppressor precursor cells in sle patients coincided with the absence of t gamma suppressor effector cells characterization of the postthymic precursor cells derived from normal donors with the aid of monoclonal antibodies of the okt series and several other markers pointed out that this population contains okt4 as well as okt8 cells further experiments demonstrated that the cells are capable of rosetting with autologous erythrocytes and do not bear fc receptors for igm or igg considering the various findings as a whole the conclusion is warranted that the postthymic suppressor precursor t cell can differentiate into a suppressor effector cell only after interaction with t suppressor inducer cells