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Interleukin-2 (IL-2), which is a growth factor for T lymphocytes, can also sometimes be inhibitory. Thus, the proliferation of CD8 + T cells in vivo is increased after the injection of a monoclonal antibody that is specific for IL-2 (IL-2 mAb), perhaps reflecting the removal of IL-2–dependent CD4 + T regulatory cells (T regs). Instead, we show here that IL-2 mAb augments the proliferation of CD8 + cells in mice simply by increasing the biological activity of preexisting IL-2 through the formation of immune complexes. When coupled with recombinant IL-2, some IL-2/IL-2 mAb complexes cause massive (>100-fold) expansion of CD8 + cells in vivo, whereas others selectively stimulate CD4 + T regs. Thus, different cytokine-antibody complexes can be used to selectively boost or inhibit the immune response.
Boyman et al. (Thu,) studied this question.