Fig. 5.

tpCD4⁺ T cells protect from melanoma. a Scheme, and (b) results of the proof-of-concept experiment to test tpCD4⁺ T-cell ability to activate CD8⁺ T cells that recognize and eliminate the tumour. OVA-expressing B16 melanoma cells (5 × 10⁵) were injected s.c. in the mid-right flank of recipient mice. All groups (9 mice per group) were adoptively transferred i.v. with naive CD8⁺ T cells from OT-I mice, together with PBS (group 1, blue), Listeria-WT tpCD4⁺ T cells (group 2, green) or Listeria-OVA tpCD4⁺ T cells (group 3, magenta). Tumours were monitored every 2–3 days. In b, each dot represents tumour size in one mouse measured at the indicated time. Mice with tumours ≥ 300 mm² were killed to avoid unnecessary suffering. The percentage of survival is indicated