Antibody-mediated CD4⁺ T-cell depletion is followed by increased CD4⁺ T-cell proliferation in the BM. Levels of T-cell proliferation were longitudinally assessed during antibody-mediated depletion of CD4⁺ cells in 3 healthy SMs and 3 healthy RMs. (A) Representative examples of the levels of CD4⁺ T cells before and after depletion in the PB and BM of a representative SM (left) and RM (right). (B) Average percentage of CD4⁺Ki-67⁺ T cells in the BM and PB before and at different time points after CD4 depletion in SMs (left) and RMs (right). (C) Average percentage of CD8⁺Ki-67⁺ T cells in the BM and PB before and at different time points after CD4 depletion in SMs (left) and RMs (right). The dotted lines in panels B and C indicate the timing of anti-CD4 monoclonal antibody administrations. Because of the extremely low level of CD4⁺ T cells, their levels of proliferation could not be determined at day 0 in RMs.