Induction of Cytotoxic T Lymphocyte Antigen 4 (Ctla-4) Restricts Clonal Expansion of Helper T Cells

• DOI: 10.1084/jem.194.7.893
• Publication Date: 2002-07-26T16:48:33Z
• Authors: Alden M. Doyle; Alan C. Mullen; Alejandro V. Vill...; Anne S. Hutchins; Frances A. High; Hubert W. Lee; Craig B. Thompson; Steven L. Reiner
• Keywords: 0301 basic medicine; Mice, Inbred BALB C; Immunoconjugates; Cell Death; T-Lymphocytes, Helper-Inducer; Lymphocyte Activation; Antigens, Differentiation; Abatacept; Mice, Inbred C57BL; Mice; 03 medical and health sciences; 0302 clinical medicine; Gene Expression Regulation; Antigens, CD; Animals; CTLA-4 Antigen; Cell Division; Immunosuppressive Agents

Cytotoxic T lymphocyte antigen (CTLA)-4 plays an essential role in immunologic homeostasis. How this negative regulator of T cell activation executes its functions has remained controversial. We now provide evidence that CTLA-4 mediates a cell-intrinsic counterbalance to restrict the clonal expansion of proliferating CD4+ T cells. The regulation of CTLA-4 expression and function ensures that, after ∼3 cell divisions of expansion, most progeny will succumb to either proliferative arrest or death over the ensuing three cell divisions. The quantitative precision of the counterbalance hinges on the graded, time-independent induction of CTLA-4 expression during the first three cell divisions. In contrast to the limits imposed on unpolarized cells, T helper type 1 (Th1) and Th2 effector progeny may be rescued from proliferative arrest by interleukin (IL)-12 and IL-4 signaling, respectively, allowing appropriately stimulated progeny to proceed to the stage of tissue homing. These results suggest that the cell-autonomous regulation of CTLA-4 induction may be a central checkpoint of clonal expansion of CD4+ T cells, allowing temporally and spatially restricted growth of progeny to be dictated by the nature of the threat posed to the host.