T-helper cells recruit cytotoxic T-cells primarily through which interleukin?

Interleukin-2 (IL-2) is the primary cytokine secreted by activated T-helper cells (CD4+) that promotes the proliferation and activation of cytotoxic T-cells (CD8+). IL-2 is also an autocrine growth factor for T-helper cells themselves. IL-1 is produced primarily by macrophages and activates T-helper cells. IL-3 stimulates hematopoietic progenitor cells. IL-4 promotes B-cell differentiation and IgE production. IL-2 is the central mediator linking T-helper cell activation to cytotoxic T-cell recruitment.