CD8+ cytotoxic T-APC stimulate central memoiry CD8+ T cell responses via acquired peptide-MHC class I complexes and CD80 costimulation, and RL-2 secretion

We previously showed that naive CD4(+) Th cells acquire peptide-MHC class I (pMHC 1) and costimulatory molecules from OVA-pulsed dendritic cells(DCOVA), and act as Th-APCs in stimulation of CD8(+)CTL responses. In this study, we further demonstrated that naive CD8(+) cytotoxic T (Tc) cells also acquire pMHC I and costimulatory CD54 and CD80 molecules by DCOVA stimulation, and act as Tc-APC. These Tc-APC can play both negative and positive modulations in antitumor immune responses by eliminating DCOVA and neighboring Tc-APC, and stimulating OVA-specific CD8(+) central memory T responses and antitumor immunity. Interestingly, the stimulatory effect of Tc-APC is mediated via its IL-2 secretion and acquired CD80 co-stimulation, and is specifically targeted to OVA-specific CD8(+) T cells in vivo via its acquired pMHC I complexes. These principles could be applied to not only antitumor immunity, but also other immune disorders (e.g., autoimmunity).