Signaling through CD28 and CTLA-4 controls two distinct forms of T cell anergy
Andrew D. Wells, … , Jeffrey A. Bluestone, Laurence A. Turka
Andrew D. Wells, … , Jeffrey A. Bluestone, Laurence A. Turka
Published September 15, 2001
Citation Information: J Clin Invest. 2001;108(6):895-904. https://doi.org/10.1172/JCI13220.
View: Text | PDF
Article Article has an altmetric score of 7

Signaling through CD28 and CTLA-4 controls two distinct forms of T cell anergy

Abstract

Primary T cell proliferative responses to TCR ligation plus CD28 costimulation are surprisingly heterogeneous. Many cells that enter G1 fail to progress further through the cell cycle, and some of these cells subsequently fail to divide upon restimulation, even in the presence of IL-2. Such IL-2–refractory anergy is distinct from the IL-2–reversible anergy induced by TCR occupancy in the absence of CD28 costimulation. Here, we focus on the contributions of cell cycle progression and costimulatory (CD28/CTLA-4) signals in the regulation of anergy. We show that CD28 costimulation is not sufficient for anergy avoidance and that activated T cells must progress through the cell cycle in order to escape anergy. Induction of this “division-arrest” form of anergy requires CTLA-4 signaling during the primary response. Also, cell division per se is not sufficient for anergy avoidance: the few T cells that undergo multiple rounds of cell division during overt CD28 costimulatory blockade do not escape the ultimate induction of clonal anergy. Anergy avoidance by primary T cells is thus a multistep process: in order to participate in a productive immune response, an individual T cell activated through its antigen receptor must receive CD28 costimulation and progress through the cell cycle. Anergy may be induced either through a combination of CTLA-4 signaling and the failure of cell cycle progression, or through a proliferation-independent mechanism in which TCR ligation occurs in the absence of CD28.

Authors

Andrew D. Wells, Matthew C. Walsh, Jeffrey A. Bluestone, Laurence A. Turka

×

Figure 2

Options: View larger image (or click on image) Download as PowerPoint
B7-mediated costimulation and cell division differentially regulate seco...
B7-mediated costimulation and cell division differentially regulate secondary T cell proliferation. (a–o) CFSE-labeled spleen and lymph node cells were stimulated with anti-CD3 in the presence of human IgG (a–g; first and second sets of columns in o) or CTLA4Ig (h–n; third and fourth sets of columns in o). Cultures were rested for 48 hours, and Thy1.2+ cells that had divided twice (b, d, f, i, k, and m; shaded bars in o) or had remained undivided (c, e, g, j, l, and n; open bars in o) following primary stimulation were purified by FACS. The sorted T cells were cultured with irradiated APCs and restimulated with anti-CD3 in the presence or absence of exogenous IL-2; proliferation was assessed 4 days later by flow cytometry. One representative experiment for each condition (a–g and h–n) is depicted graphically. The mean secondary mitotic events of separate experiments (n = 2 [first and second sets of columns] or n = 4 [third and fourth sets of columns]) are plotted in o. Statistically significant differences were assessed by paired t test and are denoted by brackets: *P < 0.05; ***P < 0.001. (p) Lymph node and spleen cells were cultured with anti-CD3 in combination with anti-CD28 antibody (first and second lanes) or CTLA4Ig (third and fourth lanes). The cultures were rested for 24 hours, and the T cells were restimulated with anti-CD3–coated beads for 48 hours in the presence (second and fourth lanes) or absence (first and third lanes) of IL-2. Live cells were harvested after the primary stimulus (top panels) and after the secondary stimulus (bottom panel) by isolation over Ficoll, and lysates were subjected to immunoblot analysis using antibodies against p27kip1 (top and bottom panels) or actin (data not shown). The results shown are representative of two independent experiments. (q) Primary, CFSE-labeled T cells were primed with anti-CD3 as in p and rested (top panel), and a portion of the cells were restimulated with either 50 U/ml IL-2 for 48 hours (middle panel) or PMA/ionomycin (PMA/Iono) for 24 hours (bottom panel). The live, CD4+ cells were then sorted into fractions that had divided two or more times (right lane, “D”), or had remained undivided during the culture period (left lane, “U”). The cells were lysed, and equal cell equivalents were assessed for p27kip1 content by immunoblot analysis. The data shown are representative of two independent experiments.