Memory CD4 T cells can delay tumor growth in C5⁺ hosts. Percentage of tumor-free mice following inoculation of naive A18 TCR transgenic mice (▵) and C5⁺ mice with memory CD4 T cells (▴) with 5 × 10⁵ C5-transfected LK35 tumor cells. Symbols represent individual data for groups of 5 mice. Memory T cells were derived from mice that had been injected with naive A18 TCR transgenic T cells and syngeneic DCs.