T cell involvement in the decrease of antigen-responsive B cells in aged mice.

The role of T cells in the reduced frequency of splenic B cells specific for several antigens in aged mice was studied by assessing B cell responsiveness in (a) aged nude mice and (b) irradiated young mice repopulated with splenic B cells or with Ig- bone marrow cells from young mice and T cells from aged vs. young mice. Using the fragment culture technique to assess B cells specific for 2,4-dinitrophenyl (DNP) and for (4-hydroxy-3,5-dinitrophenyl) acetyl, we found that the frequency of responsive splenic B cells in aged BALB/c nude mice was very similar to that of young nude mice. In addition, we found that in chimeric mice constructed with either bone marrow or splenic B cells from young mice and T cells from aged mice the frequency of DNP-specific splenic B cells was significantly lower than that in control chimeras constructed with T cells from young mice. These results indicate that T cells from aged mice can down regulate B cell responsiveness and that a mature, naive B cell may be its possible target. The results of both experimental approaches are consistent with a role for T cells in the regulation of responsive B cells in aging.