In vitro tolerance induction of neonatal murine B cells as a probe for the study of B-cell diversification.

The susceptibility to in vitro tolerance induction has been implicated as a characteristic of B cells early in their development, since DNP-reactive B cells are tolerizable only during the first days after birth, and 25% of adult bone marrow cells are tolerizable. In the present study, a modification of the in vitro splenic focus technique was utilized to determine if PC-specific B cells, by virtue of their late expression (approximately 1 wk post-parturition), also display susceptibility to tolerance induction. The results demonstrate that at 7-10 days after birth, when over 90% of the DNP-specific splenic B cells are resistant to tolerance induction, the majority of PC-specific B cells are tolerizable. These results re-emphasize tolerance susceptibility as a characteristic of developing clones, confirm the late acquisition of PC-specific B cells, and support the contention that the acquisition of the specificity repertoire is a highly ordered, specifically predetermined process which is independent of antigen-driven events.