While there is considerable overlap of cytokine activity on lymphocytes, effects can be stimulatory or inhibitory depending on the cytokine. IL-21 only increases proliferation of T cells stimulated with anti-CD3 or antigen, but can augment responses to other gamma(c) cytokines. IL-7 acts on developing B cells but not mature cells of this lineage. IL = interleukin, NK = natural killer, NKT = natural killer-T cell, Treg = regulatory T cell