During an immune reaction, some antigen-experienced CD4 T cells relocate from
secondary lymphoid organs (SLOs) to the bone marrow (BM) in a CD49b-dependent
manner and reside and rest there as professional memory CD4 T cells. However,
it remains unclear how the precursors of BM memory CD4 T cells are generated
in the SLOs. While several studies have so far shown that B cell depletion
reduces the persistence of memory CD4 T cells in the spleen, we here show that
B cell depletion enhances the establishment of memory CD4 T cells in the BM
and that B cell transfer conversely suppresses it. Interestingly, the number
of antigen-experienced CD4 T cells in the BM synchronizes the number of
CD49b+T-bet+ antigen-experienced CD4 T cells in the spleen. CD49b+T-bet+
antigen-experienced CD4 T cells preferentially localize in the red pulp area
of the spleen and the BM in a T-bet-independent manner. We suggest that B
cells negatively control the generation of CD49b+T-bet+ precursors of resting
memory CD4 T cells in the spleen and may play a role in bifurcation of
activated effector and resting memory CD4 T cell lineages