Membrane and metabolic requirements for tolerance induction of neonatal B cells.

The metabolic requirements of tolerance induction of immature B cells has been analyzed through the use of various putative inhibitors. The study utilizes the splenic fragment assay in which tolerance induction of individual B cells can be examined. Concentrations of inhibitors were determined which, if removed after the first 18 hr of culture, before antigenic stimulation, had no inhibitory effects. Thus, by adding tolerogen in the presence or absence of inhibitor during the first 18 hr of culture, the effect of that inhibitor on tolerance could be assessed. By using this protocol, the data indicate that several metabolic functions of the cell are necessary for tolerance induction to occur, including RNA biosynthesis, DNA biosynthesis, and a methyltransferase reaction, because drugs that interfere with these metabolic processes also prevent tolerance induction. Our previous studies indicated that protein biosynthesis and energy generation are also required. However, drugs that interact with the cytoskeletal structure of the cell and inhibit surface immunoglobulin capping do not interfere with tolerance induction. Moreover, colchicine, which inhibits cell division, does not inhibit B cell tolerance. Collectively, the results provide compelling evidence that the mechanism of immature B cell tolerance involves an active process requiring several metabolic activities of the cell.