Chronic activation profile of circulating CD8+ T cells in Sézary syndrome

Abstract

Sézary syndrome (SS) is a leukemic variant of cutaneous T cell lymphoma (CTCL), and the neoplastic CD4+ T cells of SS patients undergo intense clonal proliferation. Although Sézary cells have been studied extensively, studies on adaptive immunity regarding CD8+T cells are scarce. This study aimed to investigate activation marker expression in CD8+ T cells according to the differentiation stages and IL-7/IL7Rα axis responses of patients with SS. Moreover, this study aimed to verify the soluble forms of CD38, sCD127 and IL-7 in serum. Although the SS patients of our cohort had reduced numbers of CD8+ T cells, they exhibited higher percentages of CD8+CD38+ T cells, mainly effector/memory CD8+ T cells, than the control group. In contrast, down-regulated expression of the activation markers CD127/IL-7R and CD26 was found in the CD8+ T cells of SS patients. High serum levels of sCD38 and sCD127 and scarce serum levels of IL-7 were detected, emphasizing the immune activation status of SS patients. Moreover, CD8+ T cells from SS patients exhibited IL-7 unresponsiveness to STAT5 phosphorylation and Bcl-2 expression, and IL-7 priming partially restored IFNγ production. Our findings showed a chronic activation profile of CD8+ T cells, as an attenuated cytotoxic profile and impaired IL-7 responsiveness was observed, suggesting chronic activation status of CD8+ T cells in SS patients.

Keywords: CD8+ T cells; Sézary syndrome; chronic activation markers; sCD127; sCD38.

Figure 1. Up-regulation of CD38 in CD8+ T cells from SS patients

Peripheral blood CD8+ T cells from SS patients and healthy donors were assessed for memory differentiation subsets and activation markers by flow cytometry. Gating strategy: singlet, lymphocytes, CD3+, CD8+ and memory differentiation. (A) CD8+ T cells memory differentiation subsets (n = 14 SS and 19 HD), (B) Total CD127+CD8+ T cells percentage (n = 15 SS and 19 HD) and on CD8+ T cells differentiation subsets (n = 14 SS and 15 HD), (C) Total CD38+CD8+ T cells percentage (n = 16 SS and 25 HD) and on differentiation subset (n = 17 SS and 19 HD). The data are shown as median and interquartil. ^*p ≤ 0.05, ^**p ≤ 0.01, ^***p ≤ 0.001.

Figure 2. Decreased expression of CD26+ on CD8+ T cells of Sézary patients

CD8+ T cells from peripheral blood of SS patients and healthy donors were assessed for CD26+ expression by flow cytometry. PBMC were stimulated by PMA and Ionomycin or TLR 7/8 agonist (CL097). (A) Total CD26+ CD8+ T cells percentage, CD26 MFI and memory differentiation of CD8+CD26+ T cells (n = 15 SS and 19 HD), (B) CD38 and CD127 (n = 15 SS and 19 HD) expression on CD8+CD26+ and CD8+CD26- T cells, (C) CD69 and PD-1 expression, and TNF production on CD8+ T cells (n = 9 SS and 10 HD). The data are shown as median and interquartil. ^*p ≤ 0.05, ^**p ≤ 0.01, ^***p ≤ 0.001 when compared between groups and ^# p ≤ 0.05, ^##p ≤ 0.01 when compared with the same group.

Figure 3. Impaired response to IL-7 of CD8+ T cells from Sézary patients

IL-7-signaling on CD8+ T cells from PBMC of SS patients and healthy donors was evaluated for STAT5 phosphorylation, Bcl-2 and CD95/Fas expression and TNF and IFNγ production by flow cytometry. Serum soluble CD127 (IL-7Rα), CD38 and IL-7 were evaluated by ELISA and flow cytometry, respectively (n = 15 SS and 28 HD). (A) serum IL-7, (B) serum sCD127/IL-7Rα and sCD38, (C) STAT5p (n = 6 SS and 7 HD), (D) Bcl-2 expression (n = 5 SS and 7 HD) and (E) CD95/Fas expression, TNF and IFNγ production induced by PMA and Ionomycin stimulation with previously IL-7 priming (n = 6 SS and 7 HD). The data are shown as median and interquartil. ^*p ≤ 0.05, ^**p ≤ 0.01, ^***p ≤ 0.001 when compared between groups and ^#≤ 0.05 when compared with the same group.