A pivotal role for CC chemokine receptor 5 in T-cell migration to tumor sites induced by interleukin 12 treatment in tumor-bearing mice.

Interleukin (IL) 12 treatment in the CSA1M and OV-HM, but not in Meth A tumor models,induces tumor regression that is associated with T-cell migration to tumor sites.Here, we investigated the role of the CC chemokine receptor (CCR)5 in T-cell migration induced after IL-12 treatment. In the two IL-12-responsive tumor models (CSA1M and OV-HM), IL-12 treatment up-regulated the mRNA expression of CCR5 in splenic T cells as well as ligands for CCR5, such as macrophage inflammatory protein (MIP) 1alpha and MIP-1beta in tumor masses. In contrast, the expression of CCR5 in spleens and MIP-1alpha/MIP-1beta in tumor masses was marginally induced before and even after IL-12 treatment in the Meth A model in which T-cell migration is not observed. T cells infiltrating tumor masses in the former two IL-12-responsive models expressed CCR5. Administration of a synthetic CCR5 antagonist TAK-779 to tumor-bearing mice during IL-12 immunotherapy prevented T-cell migration and tumor regression. Furthermore, anti-CCR5 antibody was found to inhibit T-cell migration in the lymphoid cell migration assay. Namely, although splenic T cells prepared from IL-12-treated CSA1M or OV-HM-bearing mice migrated into the corresponding tumor masses in recipient mice, the migration was inhibited when donor T cells were treated with anti-CCR5 antibody before the injection. These results indicate a critical role for CCR5 in the induction of T-cell migration to tumor sites after IL-12 treatment.

A role for endogenous IL-12 in tumor immunity: IL-12 is required for the acquisition of tumor-migratory capacity by T cells and the development of T cell-accepting capacity in tumor masses.

Interleukin (IL)-12 plays a central role in the initiation and regulation of T cell-mediated immune responses. The present study investigated how IL-12, endogenously produced during tumor vaccination, functions for anti-tumor immune responses. Mice were given anti-IL-12 monoclonal antibody during immunization with attenuated syngeneic tumor cells. Splenic T cells from anti-IL-12-treated immunized mice exhibited comparable levels of tumor-neutralizing activity with those from tumor-immunized mice without anti-IL-12 treatment. When these two groups of mice were directly challenged with viable tumor cells, tumor rejection was induced only in anti-IL-12-untreated mice. T cell infiltration was observed at the site of tumor challenge in these mice, whereas such a T cell infiltration did not occur in anti-IL-12-treated mice. The tumor-migratory capacity was directly assessed by transferring spleen cells from tumor-immunized mice into syngeneic, tumor-bearing recipient mice and by quantitating donor cells migrating into recipients' tumor masses. T cells from anti-IL-12-treated tumor-immunized mice were found to exhibit a markedly reduced tumor-migratory capacity when compared with that of anti-IL-12-untreated mice. Moreover, the migration of T cells from anti-IL-12-untreated mice to tumor masses prepared in anti-IL-12-treated mice was severely reduced. These results indicate that endogenously produced IL-12 has dual roles in anti-tumor-immune resistance: One is to confer T cells with a tumor-migratory capacity, and the other is to allow tumor masses to develop the capacity to accept tumor-migrating T cells.

Induction of tumor regression by administration of B7-Ig fusion proteins: mediation by type 2 CD8+ T cells and dependence on IL-4 production.

CD28 signals contribute to either type 1 or type 2 T cell differentiation. Here, we show that administration of B7.2-Ig fusion proteins to tumor-bearing mice induces tumor regression by promoting the differentiation of antitumor type 2 CD8(+) effector T cells along with IL-4 production. B7.2-Ig-mediated regression was not induced in IL-4(-/-) and STAT6(-/-) mice. However, it was elicited in IFN-gamma(-/-) and STAT4(-/-) mice. By contrast, IL-12-induced tumor regression occurred in IL-4(-/-) and STAT6(-/-) mice, but not in IFN-gamma(-/-) and STAT4(-/-) mice. Moreover, B7.2-Ig treatment was effective in a tumor model not responsive to IL-12. B7.2-Ig administration elicited elevated levels of IL-4 production. Tumor regression was predominantly mediated by CD8(+) T cells, although the induction of these effector cells required CD4(+) T cells. Tumor regression induced by CD8(+) T cells alone was inhibited by neutralizing the IL-4 produced during B7.2-Ig treatment. Thus, these results indicate that stimulation in vivo of CD28 with B7.2-Ig in tumor-bearing mice results in enhanced induction of antitumor type 2 CD8(+) T cells (Tc2) leading to Tc2-mediated tumor regression.

A non-peptide CCR5 antagonist inhibits collagen-induced arthritis by modulating T cell migration without affecting anti-collagen T cell responses.

The chemokine receptors CCR5 and CXCR3 have been implicated as playing a central role in directing a Th1 inflammatory response. Here, we investigated whether a synthetic CCR5 antagonist affects the process of T cell migration to sites of inflammation. Immunization of DBA/1 mice with type II collagen resulted in typical arthritis, which is associated with cellular infiltration. Treatment with a CCR5 antagonist strikingly affected the development of arthritis by reducing both incidence and severity of disease. There was no substantial difference between collagen-immunized mice with and without antagonist treatment in the induction of anti-collagen T cell responses and the capacity to produce IL-12. This endogenous IL-12 functioned to induce comparable levels of CCR5 in these two immunized groups of T cells. Whereas a massive infiltration of inflammatory cells including CCR5(+) T cells occurred in the joints of mice immunized without antagonist, cellular infiltration in the antagonist-treated group was only marginal. These results indicate that administration of a CCR5 antagonist inhibits the development of arthritis not by affecting the generation of collagen-sensitized T cells but by interfering with their migration to joint lesions.

Induction of the chemokine receptor CXCR3 on TCR-stimulated T cells: dependence on the release from persistent TCR-triggering and requirement for IFN-gamma stimulation.

The chemokine receptor CXCR3 has been shown to play a key role in the recruitment of T cells to sites of inflammation such as allografts. Here, we investigated which signals and conditions areresponsible for CXCR3 induction. CXCR3 was induced on T cells that were stimulated with anti-CD3 plus anti-CD28 monoclonal antibodies and then recultured without any external stimuli. CXCR3 expression was inhibited when TCR stimulation was persistent in the reculture. CXCR3 induction also depended on the stimulation with IFN-gamma because CXCR3 expression was not induced in IFN-gamma-deficient T cells. The induction of another Th1 chemokine receptor CCR5 absolutely required IL-12 stimulation and STAT4 involvement. In contrast, CXCR3 was induced on STAT4-deficient T cells independently of IL-12 stimulation as long as IFN-gamma was produced as a result of potent TCR stimulation. These results show that CXCR3 induction on TCR-triggered T cells requires the release of these T cells from persistent TCR signaling and the stimulation with IFN-gamma and also indicate the differential regulatory mechanisms underlying the induction of two Th1 chemokine receptors.