The role of CD4+ T cells in tumor and chronic viral immune responses

Immunotherapies are mainly aimed to promote a CD8+ T cell response rather than a CD4+ T cell response as cytotoxic T lymphocytes (CTLs) can directly kill target cells. Recently, CD4+ T cells have received more attention due to their diverse roles in tumors and chronic viral infections. In antitumor and antichronic viral responses, CD4+ T cells relay help signals through dendritic cells to indirectly regulate CD8+ T cell response, interact with B cells or macrophages to indirectly modulate humoral immunity or macrophage polarization, and inhibit tumor blood vessel formation. Additionally, CD4+ T cells can also exhibit direct cytotoxicity toward target cells. However, regulatory T cells exhibit immunosuppression and CD4+ T cells become exhausted, which promote tumor progression and chronic viral persistence. Finally, we also outline immunotherapies based on CD4+ T cells, including adoptive cell transfer, vaccines, and immune checkpoint blockade. Overall, this review summarizes diverse roles of CD4+ T cells in the antitumor or protumor and chronic viral responses, and also highlights the immunotherapies based on CD4+ T cells, giving a better understanding of their roles in tumors and chronic viral infections.

Essential role of CD4+ T cells for the activation of group 2 innate lymphoid cells during respiratory syncytial virus infection in mice

Aim: To investigate whether and how CD4⁺ T cells contribute to ILC2 activation during respiratory syncytial virus (RSV) infection. Methods: The methods of flow cytometry, quantitative PCR and ELISA were used in the present study. Results: Depletion of CD4⁺ T cells diminished the numbers of lung ILC2s as well as their ability to produce type 2 cytokines. CD4⁺ T cell-mediated ILC2 activation is related to IL-2. The main cellular source of IL-2 was CD4⁺ T cells. Depletion of CD4⁺ T cells decreased IL-2 levels in the lungs of RSV-infected mice. IL-2 can directly stimulate ILC2 proliferation and promote ILC2s to produce cytokines. Treatment of mice with neutralizing anti-IL-2 monoclonal antibodies diminished ILC2 activation. Conclusion: These results suggest that CD4⁺ T cells contribute to RSV-induced ILC2 activation partly via producing IL-2.

T-cell transcriptomics from peripheral blood highlights differences between polymyositis and dermatomyositis patients

BACKGROUND

Polymyositis (PM) and dermatomyositis (DM) are two distinct subgroups of idiopathic inflammatory myopathies, a chronic inflammatory disorder clinically characterized by muscle weakness and inflammatory cell infiltrates in muscle tissue. In PM, a major component of inflammatory cell infiltrates is CD8+ T cells, whereas in DM, CD4+ T cells, plasmacytoid dendritic cells, and B cells predominate. In this study, with the aim to differentiate involvement of CD4+ and CD8+ T-cell subpopulations in myositis subgroups, we investigated transcriptomic profiles of T cells from peripheral blood of patients with myositis.

METHODS

Total RNA was extracted from CD4+ T cells (PM = 8 and DM = 7) and CD8+ T cells (PM = 4 and DM = 5) that were isolated from peripheral blood mononuclear cells via positive selection using microbeads. Sequencing libraries were generated using the Illumina TruSeq Stranded Total RNA Kit and sequenced on an Illumina HiSeq 2500 platform, yielding about 50 million paired-end reads per sample. Differential gene expression analyses were conducted using DESeq2.

RESULTS

In CD4+ T cells, only two genes, ANKRD55 and S100B, were expressed significantly higher in patients with PM than in patients with DM (false discovery rate [FDR] < 0.05, model adjusted for age, sex, HLA-DRB1*03 status, and RNA integrity number [RIN]). On the contrary, in CD8+ T cells, 176 genes were differentially expressed in patients with PM compared with patients with DM. Of these, 44 genes were expressed significantly higher in CD8+ T cells from patients with PM, and 132 genes were expressed significantly higher in CD8+ T cells from patients with DM (FDR < 0.05, model adjusted for age, sex, and RIN). Gene Ontology analysis showed that genes differentially expressed in CD8+ T cells are involved in lymphocyte migration and regulation of T-cell differentiation.

CONCLUSIONS

Our data strongly suggest that CD8+ T cells represent a major divergence between PM and DM patients compared with CD4+ T cells. These alterations in the gene expression in T cells from PM and DM patients might advocate for distinct immune mechanisms in these subphenotypes of myositis.

Enhanced Th1 and Th17 responses in peripheral blood in active non-segmental vitiligo

Accumulating studies have indicated that vitiligo, especially non-segmental vitiligo (NSV), is one kind of autoimmune diseases and CD4⁺ T cells play important roles in the pathogenesis. However, there have been very limited data on the detailed changes of each of the CD4⁺ T cell subsets in periphery in active NSV. To clarify this issue, we collected the peripheral blood mononuclear cells (PBMCs) from 30 patients with active NSV and 30 age- and sex-matched healthy controls. The percentages of circulating Th1, Th2, Th17 and Tregs were evaluated using flow cytometry and the expressions of their specific transcription factors T-bet, GATA3, RORγt and FOXP3 at mRNA level and protein levels were qualified by qPCR and flow cytometry, respectively. Meanwhile, the expression levels of IFN-γ, IL-4, TGF-β, and IL-17A in serum were measured. We found that in patients with NSV, the percentages and absolute numbers of circulating Th1 and Th17 were both significantly higher than those of healthy controls, while the percentages of Th2 and Tregs and absolute numbers showed no significant difference compared to healthy controls. Moreover, the ratios of Th1/Tregs and Th17/Tregs in circulation were both statistically elevated in active NSV. Similar results were got in qualification of their corresponding transcription factors at mRNA level and protein levels. Compared with healthy controls, the expression level of IL-17A was significantly increased in serum of patients with NSV, while the productions of IFN-γ, IL-4, TGF-β had no significant change. These data suggested that in circulating CD4⁺ T cell subsets, Th1 and Th17 played the major role in cellular immunity in the progression of vitiligo. The immune lever in circulation was inclined to effector CD4⁺ T cells not suppressor CD4⁺ T cells that may result in the loss of self-tolerance to melanocytes.