B cell infiltration of the thymic medulla in New Zealand black, New Zealand white, and (New Zealand black x New Zealand white)F1 mice. Effect of total lymphoid irradiation.

Thymuses from female (New Zealand black x New Zealand white)F1 [( NZB x NZW]F1), New Zealand black, and New Zealand white mice of different ages were examined by immunohistochemical and flow cytometric analysis. Two-and-a-half-month-old (NZB x NZW)F1 mice showed infiltration of the thymus with B cells, and by 6-8 months of age, showed a disruption of the entire medullary area. More than 80% of the thymic B cells had the phenotypic characteristics of conventional B cells (IgM+, IgD+, Ly-1-). Total lymphoid irradiation induced a marked depletion of medullary B cells and a restoration of the thymic architecture.