CD4+ Th-APC with Acquired Peptide/MHC Class I and II Complexes Stimulate Type 1 Helper CD4+ and Central Memory CD8+ T Cell Responses

Abstract

T cell-T cell Ag presentation is increasingly attracting attention. We previously showed that the in vitro OVA-pulsed dendritic cell (DCOVA)-activated CD4+ Th cells acquired OVA peptide/MHC (pMHC) class I and costimulatory molecules such as CD54 and CD80 from DCOVA and acted as CD4+ Th-APC capable of stimulating OVA-specific CD8+ CTL responses. In this study, we further applied the OVA-specific TCR-transgenic OT I and OT II mice with deficiency of various cytokines or costimulatory molecule genes useful for studying the molecular mechanisms underlying in Th-APC’s stimulatory effect. We demonstrated that DCOVA-stimulated OT II CD4+ Th-APC also acquired costimulatory molecules such as CD40, OX40L, and 4-1BBL and the functional pMHC II complexes by DCOVA activation. CD4+ Th-APC with acquired pMHC II and I were capable of stimulating CD4+ Th1 and central memory CD8+44+CD62LhighIL-7R+ T cell responses leading to antitumor immunity against OVA-expressing mouse B16 melanoma. Their stimulatory effect on CD8+ CTL responses and antitumor immunity is mediated by IL-2 secretion, CD40L, and CD80 signaling and is specifically targeted to CD8+ T cells in vivo via acquired pMHC I. In addition, CD4+ Th-APC expressing OVA-specific TCR, FasL, and perforin were able to kill DCOVA and neighboring Th-APC expressing endogenous and acquired pMHC II. Taken together, we show that CD4+ Th-APC can modulate immune responses by stimulating CD4+ Th1 and central memory CD8+ T cell responses and eliminating DCOVA and neighboring Th-APC. Therefore, our findings may have great impacts in not only the antitumor immunity, but also the regulatory T cell-dependent immune tolerance in vivo.

Intercellular Trogocytosis Plays an Important Role in Modulation of Immune Responses

“…Interestingly, the stimulatory effect of CD4 + Th1-APCs is mediated through its endogenous CD40L and acquired CD80 costimulation and IL-2 secretion (84). Importantly, the acquired pMHC I complexes on CD4 + Th1-APCs play an important role in targeting the stimulatory effect of CD4 + Th-APCs to naïve CD8 + T cells in vivo (84). Similarly, we have further demonstrated that naїve CD8 + cytotoxic T (Tc) cells also acquire pMHC I and costimulatory CD54 and CD80 molecules through DC OVA stimulation, and act as Tc-APCs.…”

CD4+ T cell-released exosomes inhibit CD8+ cytotoxic T-lymphocyte responses and antitumor immunity

“…12 The OVA-specific CD4 1 T cells were incubated with or without 0.5 mM carboxyfluorescein diacetate succinimidyl ester (CFSE) and then cultured in serum-free AIM-V medium (Invitrogen Corp., Carlsbad, CA, USA) with IL-2 (20 U/ ml) for 24 h. EXO were purified from the T-cell culture supernatants by differential ultracentrifugation, and protein content was quantified by Bradford assay. 13 DC OVA -activated OTII CD4 1 T cell-released EXO and CFSE-labeled OTII CD4…”

“…Six days later, cells from tail blood samples of immunized mice were stained with a PE-H-2K b /OVAI tetramer and FITC-anti-CD8 Ab according to the manufacturer's protocol and analyzed by flow cytometry. 12 …”

“…In this study, we activated CD4 1 T cells derived from OVA-specific T-cell receptor (TCR) transgenic OTII mice 12 in vitro with ovalbumin (OVA)-pulsed dendritic cells (DC OVA ) and purified EXO from culture supernatants of the CD4 1 T cells by differential ultracentrifugation. We assessed the effect of EXO on DC OVA -mediated CD8…”

“…The highly lung metastatic B16 mouse melanoma (BL6-10) and OVA-transfected BL6-10 (BL6-10 OVA ) cell lines were generated in our laboratory. 12 Female C57BL/6 (B6, H-2K b ) mice were obtained from Charles River Laboratories (St Laurent, Que., Canada). The OVA 323-339 -specific TCR-transgenic (OTII) mice on a C57BL/6 background were obtained from the Jackson Laboratory (Bar Harbor, MA, USA).…”