IL-2 Regulates Perforin and Granzyme Gene Expression in CD8+ T Cells Independently of Its Effects on Survival and Proliferation

Abstract

Perforin and the serine protease granzymes are key effectors of CD8+ T cell granule-mediated cytotoxicity, but the requirements for their expression remain largely undefined. We show in this study that IL-2 increased the expression of perforin and granzyme A, B, and C mRNA; intracellular granzyme B protein levels; and cytolytic function in a dose-dependent manner during primary activation of murine CD8+ T cells in vitro. Two approaches showed that these responses were not a consequence of the effects of IL-2 on cell survival and proliferation. First, IL-2 enhancement of perforin and granzyme expression was equivalent in CD8+ T cells from wild-type and bcl-2 transgenic mice, although only the latter cells survived in low concentrations or the absence of added IL-2. This property of bcl-2 transgenic T cells also allowed the demonstration that induction of granzyme A, B, and C mRNA and granzyme B protein required exogenous IL-2, whereas induction of perforin and IFN-γ expression did not. Second, analysis of perforin and granzyme mRNA levels in cells separated according to division number using the dye CFSE showed that the effects of IL-2 were unrelated to division number. Together, these findings indicate that IL-2 can directly regulate perforin and granzyme gene expression in CD8+ T cells independently of its effects on cell survival and proliferation.

IL‐2 promotes the function of memory‐like autoregulatory CD8+T cells but suppresses their development via FoxP3+Treg cells

“…We have presented data showing that the memory-like autoregulatory CD8 + T cells developing in Il2 haploinsufficient hosts have defective IFN-γ production capacity as well as impaired APC-killing activity, two of the mechanisms that they employ to suppress T-cell responses [8]. This is in agreement with other studies showing that IL-2 controls the expression of IFN-γ, perforin, and granzymes in activated CD8 + T cells [33], as well as the effector function and IFN-γ production of memory CD8 + T cells after secondary antigenic challenge [11].These observations further predict that responsiveness to pMHC-NP therapy will be influenced by genetically determined variations in IL-2 production or IL-2 receptor expression. Although NRP-V7/K d -NP treatment of Il2-hemizygous NOD mice led to increased expansion of tetramer + autoregulatory CD8 + T cells, the expanded cells might not be as efficient as their Il2-homozygous counterparts in suppressing anti-islet autoimmunity, a possibility that will be the subject to future investigation.…”

Heterogeneity of Effector Phenotype for Acute Phase and Memory Influenza A Virus-Specific CTL

“…Also, despite the high frequency of GzmB mRNA, the level of protein staining within long-lived memory CTLs was generally very low, indicating that the regulation of GzmB expression is more at the level of translation than of transcription. Both IL-2 and IL-15 have been demonstrated to enhance transcription of Pfp and GrzB mRNA (38,39). Given that IL-15 is important for maintenance of memory CTL homeostasis (40,41), it is tempting to speculate that the actions of IL-15 may also play a role in maintaining effector mRNA transcription in long-term influenza-specific memory CTL.…”

Death by a Thousand Cuts: Granzyme Pathways of Programmed Cell Death

“…Previously, the pleiotropic properties of IL-2 made dissociating its effects on T cell survival and proliferation from its effects on gene expression difficult (24). However, a recent study in mice showed that IL-2 regulates perforin and granzyme expression directly and independently of its effect on CD8 + T cell survival and proliferation (25). Mice genetically deficient in IL-2 retain the ability to elicit a CTL response against many viruses, tumors, and allografts (26,27), although there are deficiencies in cytotoxicity under certain conditions (28).…”