CTLA‐4, a Negative Regulator of T‐Lymphocyte Activation

CTLA-4 (CD152) engagement can down-regulate T cell activation and promote the induction of immune tolerance. However, the strategy of attenuating T cell activation by engaging CTLA-4 has been limited by sharing of its natural ligands with the costimulatory protein CD28. In the present study, a CTLA-4-specific single-chain Ab (scFv) was developed and expressed on the cell surface to promote selective engagement of this regulatory molecule. Transfectants expressing anti-CTLA-4 scFv at their surface bound soluble CTLA-4 but not soluble CD28. Coexpression of anti-CTLA-4 scFv with anti-CD3ε and anti-CD28 scFvs on artificial APCs reduced the proliferation and IL-2 production by resting and preactivated bulk T cells as well as CD4+ and CD8+ T cell subsets. Importantly, expression of anti-CTLA-4 scFv on the same cell surface as the TCR ligand was essential for the inhibitory effects of CTLA-4-specific ligation. CTLA-4-mediated inhibition of tyrosine phosphorylation of components of the proximal TCR signaling apparatus was similarly dependent on coexpression of TCR and CTLA-4 ligands on the same surface. These findings support a predominant role for CTLA-4 function in the modification of the proximal TCR signal. Using T cells from DO11.10 and 2C TCR transgenic mice, negative regulatory effects of selective CTLA-4 ligation were also demonstrated during the stimulation of Ag-specific CD4+ and CD8+ T cells by MHC/peptide complexes. Together these studies demonstrate that selective ligation of CTLA-4 using a membrane-bound scFv results in attenuated T cell responses only when coengaged with the TCR during T cell/APC interaction and define an approach to harnessing the immunomodulatory potential of CTLA-4-specific ligation.

Section: Discussionmentioning

confidence: 83%

Blockade of T Cell Activation Using a Surface-Linked Single-Chain Antibody to CTLA-4 (CD152)

Griffin

Hong

Holman

et al. 2000

“…Thus, in this study we focused on the relative role of CTLA-4-mediated signaling during UV-induced skin tumor development. We have chosen to investigate the CTLA-4 pathway during carcinogenesis, because ligation of CTLA-4 has been associated with impaired T cell stimulation (29,30). Unfortunately, CTLA-4-deficient mice die prematurely due to a lymphoproliferative disorder.…”

mentioning

confidence: 99%

An Important Role of CD80/CD86-CTLA-4 Signaling during Photocarcinogenesis in Mice

Loser

Scherer

Krummen

et al. 2005

Although previous studies have shown that altered B7 costimulation plays a critical role in UV irradiation-induced regulation of immunity, the individual roles of the B7 receptors (CD28 and CTLA-4) or the B7 family members (CD80 and CD86) have not been explored. Thus, we investigated CTLA-4 signaling during photocarcinogenesis of chronically UV-B-exposed mice using an antagonistic anti-CTLA-4 Ab. Anti-CTLA-4-treated mice developed significantly fewer UV-induced tumors. Moreover, anti-CTLA-4 treatment induced long-lasting protective immunity because progressively growing UV tumors inoculated into anti-CTLA-4- and UV-treated mice that had not developed tumors were rejected. Next, we used mice deficient for CD80, CD86, or both in photocarcinogenesis studies to assess the relative contributions of these CTLA-4 ligands. Double-deficient mice showed significantly reduced UV-induced skin tumor development, whereas CD86−/− mice produced skin cancer earlier compared with CD80−/− and control mice. The growth of UV-induced tumors appears to be controlled by UV-induced suppressor T cells, because CD80−/−/CD86−/− mice had strongly reduced numbers of UV-induced CD4+CD25+ suppressor T cells. In vitro, CTLA-4 blockade inhibited the suppressor activity of UV-induced CD4+CD25+ T cells, suggesting that reduced photocarcinogenesis might be due to decreased numbers or function of suppressor T cells. Together, these data indicate that blocking CD80/86-CTLA-4 signaling induced immune protection against the development of UV-induced skin tumors. Furthermore, CD86-mediated costimulation appears to play a more critical role in the protection against photocarcinogenesis than CD80.

“…The interaction of B7 molecules with CD28 on naive CD4 ϩ T cells has been shown to promote Th2 subset differentiation in vivo (10) as well as in vitro (11,12). CTLA-4 is a molecule structurally related to CD28 and transiently expressed on activated T cells to bind B7 family molecules (13). The cross-linking of CTLA-4 with immobilized anti-CTLA-4 was shown to suppress IL-4 and IFN-␥ production of T cell clones (14).…”

mentioning

confidence: 99%

Polarization of Naive CD4+ T Cells Toward the Th1 Subset by CTLA-4 Costimulation

Kato

Nariuchi

2000

In this study, we examined in vitro the role of CTLA-4 costimulation in the polarization of naive CD4+ T cells toward the Th1 subset. When CTLA-4 costimulation was blocked by the inclusion of anti-CTLA-4 Fab in cultures during priming of naive CD4+ T cells with anti-CD3 in the presence of splenic adherent cells, they were polarized toward the Th2 subset. Conversely, the engagement of CTLA-4 with immobilized anti-CTLA-4 or with CD80-P815 cells polarized naive CD4+ T cells costimulated with anti-CD3 and anti-CD28 toward the Th1 subset. The CTLA-4 costimulation during priming augmented TGF-β1 mRNA accumulation in naive CD4+ T cells, and the inclusion of anti-TGF-β in cultures for priming suppressed the effect of CTLA-4 costimulation on the Th1 polarization. The addition of low doses of TGF-β1 in cultures for priming of naive CD4+ T cells enhanced the production of Th1 cytokines upon secondary stimulation, although Th2 cytokine production was not affected by the doses of TGF-β1. The CTLA-4 costimulation was also shown to suppress IL-4 production of naive CD4+ T cells upon priming. These results indicate that the costimulation against CTLA-4 drives polarization of naive CD4+ T cells toward the Th1 subset independent of IL-12 through, at least in part, the enhancement of TGF-β1 production, and it also hampers Th2 subset differentiation by affecting IL-4 production of naive CD4+ T cells.