Modulation of B and T cell subsets in mice treated with fractionated total lymphoid irradiation. I. Blockage of differentiating B cell pathways.

The effect of fractionated total lymphoid irradiation (TLI) on the maturation of B cells was examined in mice. At various times after irradiation of the mice, their spleen cells were tested for the mitogenic responses to dextran sulfate and lipopolysaccharide. In parallel the cells were stained with fluorescent anti-Thy-1 and various anti-Ig antisera, and were analyzed on a fluorescence-activated cell sorter (FACS). By comparison with normal spleen cells the cells of TLI-treated mice gave a high response to dextran sulfate and a low response to lipopolysaccharide. FACS analysis revealed that TLI-treated spleen contains elevated numbers of B cells bearing high IgM and low IgD on the surface. The B cells of TLI-treated mice retained these immature characteristics even two to four months after the last irradiation. These findings indicate that TLI causes a longlasting blockage in B cell maturation processes.