Costimulation via lymphocyte function-associated antigen 1 in the absence of CD28 ligation promotes anergy of naive CD4+ T cells

Abstract

The mechanisms controlling induction of anergy at the level of naïve CD4 ؉ T cells are poorly understood but thought to reflect limited contact with costimulatory molecules during T cell antigen receptor (TCR) ligation. To clarify this question, naïve TCR transgenic CD4 ؉ cells were exposed to specific peptide presented by transfected antigen-presenting cells (APC) expressing MHC class II molecules with defined accessory molecules. Significantly, culturing CD4 ؉ cells with APC expressing MHC II plus peptide alone elicited early TCR signaling but failed to induce either proliferation or anergy. Culture with APC expressing MHC II plus B7 molecules led to strong proliferation and T cell priming but no anergy. In marked contrast, conspicuous induction of anergy occurred after T cell culture with APC expressing MHC class II and intercellular adhesion molecule-1 (ICAM-1). Thus, at the level of naïve CD4 ؉ cells, anergy induction appears to reflect selective contact with APC expressing ICAM-1 in the absence of B7.rodent ͉ adhesion molecules T he outcome of initial T cell contact with antigen (immunity or tolerance) is important both for assuring adequate responses to infectious pathogens and preventing inappropriate responses to self-antigens. The mechanisms controlling self͞nonself discrimination are not fully understood but may hinge on the function of costimulatory molecules. For normal immune responses, it is clear that T cell stimulation involves not only T cell receptor (TCR) recognition of peptide-MHC complexes but also interactions between costimulatory receptors and their ligands on professional antigen-presenting cells (APC). CD28 molecules are the bestcharacterized costimulatory receptors on T cells. Binding of CD28 to its B7 ligands complements TCR ligation to promote immunological synapses between T cells and APC (1, 2) and ultimately the induction of sustained proliferative responses, cytokine production (e.g., IL-2 and IL-4), and expression of molecules promoting cell survival (e.g., Bcl-x L ) (3-8).When T cells recognize antigen in the absence of costimulation, however, the results are quite different. For primed T cells, TCR stimulation (signal 1) without concomitant coligation of CD28 (signal 2) induces T cell functional unresponsiveness or anergy characterized by the failure to proliferate or make IL-2 on reexposure to antigen presented in the context of optimal costimulation (8-12).Although this paradigm for anergy induction is well established for T cell clones and lines, there is considerable controversy as to whether delivery of signal 1 alone also induces anergy at the level of naïve CD4 ϩ T cells. In the studies of Lechler and colleagues (13), exposure of unprimed CD4 ϩ T cells to immobilized anti-CD3 mAb was shown to render the surviving cells profoundly unresponsive to subsequent mitogen stimulation. The relevance of this finding to physiological recognition of MHC-peptide on normal APC is somewhat unclear, because the affinity of the TCR for peptide-MHC complexes is more than 1,000-fold lowe...

The Role of Intercellular Adhesion Molecule-1/LFA-1 Interactions in the Generation of Tumor-Specific CD8+ T Cell Responses

“…In contrast to our findings with CD8 ϩ T cells, costimulatory activity provided through LFA-1 on CD4 ϩ T cells favored limited proliferation, apoptosis and anergy (20,29,30). This may indicate that CD4 ϩ T cells have different costimulatory requirements to CD8 ϩ T cells.…”

Targeting LFA-1 Synergizes with CD40/CD40L Blockade for Suppression of Both CD4-Dependent and CD8-Dependent Rejection

“…Thus, these two costimulatory pathways have opposite effects on in vitro Th2 cytokine production (34). Interestingly, culture of CD4 + T cells with engineered APCs expressing MHC II plus B7 molecules prompts strong proliferative responses and T-cell priming but no anergy, whereas similar T-cell culture with APCs expressing MHC class II and intercellular adhesion molecule-1 (ICAM-1) results in anergy of CD4 + T cells (53).…”

Naive T Cells Are Resistant to Anergy Induction by Anti-CD3 Antibodies

“…Although it has been clearly established that signals delivered by the APC are required for optimal stimulation of naive T cells, the extent to which these cells are sensitive to anergy induction by TCR engagement in the absence of costimulation is still a matter of debate. A series of in vitro observations indicate that engagement of the TCR of a naive T cell by an Ag/ MHC complex in the absence of costimulation represents a neutral event (11,12). In particular, naive T cells are resistant to anergy induction by Ag pulsed on 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide-fixed APC, a classical protocol leading to unresponsiveness of T cell clones (37).…”