Modulation of B and T cell subsets in mice treated with fractionated total lymphoid irradiation. II. Tolerance susceptibility of B cell subsets.

Total lymphoid irradiation (TLI) results in long-lasting changes in the characteristics of both T and B cells suggestive of arrested maturation. A characteristic feature of immature B cells is their high susceptibility to tolerance induction. This study examines the susceptibility to tolerance to bovine serum albumin (BSA) of TLI-treated mice. Two experimental protocols were designed. In the first, tolerance to BSA was induced in TLI-treated adult (BALB/c X C57BL/6)F1 mice, and the ability of B cells of those mice to respond to BSA was assessed in an adoptive transfer system. In the second experimental protocol, tolerance was induced in adoptive hosts reconstituted with purified B cells originating from TLI-treated mice and with splenic T cells of normal, untreated mice. Results obtained in these two systems clearly demonstrated that splenic B cells of TLI-treated mice are highly susceptible to tolerance induction. This high susceptibility of B cells is linked neither with the elevation of immature T cells nor with induced T suppressor cells which arise due to the long-term malfunction of the thymus. Tolerance could be induced in TLI cells even 4 months after termination of the treatment. Thus, maturation processes of B cells in TLI-treated mice are arrested for long periods of time.