Progressive Differentiation and Commitment of CD8+ T Cells to a Poorly Cytolytic CD8low Phenotype in the Presence of IL-4

Abstract

Exposure to IL-4 during activation of naive murine CD8+ T cells leads to generation of IL-4-producing effector cells with reduced surface CD8, low perforin, granzyme B and granzyme C mRNA, and poor cytolytic function. We show in this study that maximal development of these cells depended on exposure to IL-4 for the first 5 days of activation. Although IL-4 was not required at later times, CD8 T cell clones continued to lose surface CD8 expression with prolonged culture, suggesting commitment to the CD8low phenotype. This state was reversible in early differentiation. When single CD8low cells from 4-day cultures were cultured without IL-4, 65% gave rise to clones that partly or wholly comprised CD8high cells; the proportion of reverted clones was reduced or increased when the cells were cloned in the presence of IL-4 or anti-IL-4 Ab, respectively. CD8 expression positively correlated with perforin and granzyme A, B, and C mRNA, and negatively correlated with IL-4 mRNA levels among these clones. By contrast, most CD8low cells isolated at later time points maintained their phenotype, produced IL-4, and exhibited poor cytolytic function after many weeks in the absence of exogenous IL-4. We conclude that IL-4-dependent down-regulation of CD8 is associated with progressive differentiation and commitment to yield IL-4-producing cells with little cytolytic activity. These data suggest that the CD4−CD8− cells identified in some disease states may be the product of a previously unrecognized pathway of effector differentiation from conventional CD8+ T cells.

Low‐avidity CD8lo T cells induced by incomplete antigen stimulation in vivo regulate naive higher avidity CD8hi T cell responses to the same antigen

“…Both CD8a and CD8b chain expression were lowered to approximately 50% of unmanipulated control mice (Fig. 1b), similar to CD8ab lo T cells generated in vitro by IL-4 exposure during antigen stimulation [19,20]. These data indicate no bias towards one co-receptor chain as observed with models of CD8aa regulatory cells [27].…”

“…We show that at these higher ratios, CD8 lo regulatory cells effectively deviate naive CD8 + T cell responses to HY antigen from Th1 / Tc1 to Th2 / Tc2 responses. This T cell polarization by immunoregulatory CD8 + T cells has been previously described in a variety of systems [15,20,44,45]. In particular, CD8 lo T cells were found to produce IL-4 cytokine after high avidity in vitro stimulation in the presence of .…”

“…We argue that these observations are CD8 + examples of the peripheral dynamic T cell "avidity regulation" model, in which T cell clones with certain avidity for cognate antigen are selectively suppressed [17,21,22], in this case by stable down-regulation of CD8 expression, which greatly impacts the ability of the CD8 + T cell to respond to low avidity antigens [17]. Here we describe that such CD8 lo T cells, despite being significantly nonresponsive to antigen per se [17][18][19][20] can also mediate dose-dependent suppression of naive, but not memory, CD8 + T cell proliferation to HY antigen in vitro. When adoptively transferred to naive female B6 recipients, HYspecific CD8 lo T cells prolong male skin graft survival in vivo.…”

“…It has been argued that CD8 lo T cells are an alternative, stable phenotype of CD8ab + T cells strongly favored during primary differentiation into an effector popula- tion by the presence of IL-4 and strong activating conditions in vitro [19,20,31]. We have previously shown that we can induce an equivalent CD8 lo T cell population in vivo after repeated stimulation with moderately high avidity MHC class I tetramers bearing HY peptide [18]; however, the effective "avidity window" to achieve this is quite narrow, as we observed using altered peptide ligands of HY [17].…”

Paradoxical Roles of IL-4 in Tumor Immunity

“…As early as in 1993, IL-4 was found to induce ionomycin/ phorbol myristate acetate (PMA) stimulated CD8 + T cells to differentiate into non-lytic CD4 -CD8 -T cells (34). Kienzle et al also demonstrated that culturing naïve murine CD8 + T cells in the presence of IL-4 and anti-IFNγ mAb led to the generation of CD8 low cells that were poorly cytolytic and expressed low levels of perforin and granzyme A, B and C (35,36).…”