Chemokines, chemokine receptors and CD4+CD25+ regulatory T cells

Anti-CCL22 increases regulatory T cells in CD4+ T cells of rheumatoid arthritis patients via STAT5 pathway

Abnormality in the number and function of CD4⁺CD25⁺FOXP3⁺ regulatory T cells (Tregs) in peripheral blood has been linked to the initiation and progression of rheumatoid arthritis (RA). Effect of chemokine CCL22 on the number of Tregs in CD4⁺ T cells and the underlying mechanism were investigated. Downregulation of peripheral Tregs were observed while upregulation of serum chemokine CCL22 in RA patients. Tregs count and the expression of FOXP3 (Tregs function-related maker) and phosphorylated-signal transducer and activator of transcription 5 (p-STAT5) in CD4⁺ T cells from RA patients were increased while C-C chemokine receptor 4 (CCR4) was decreased by anti-CCL22 antibody, however, recombinant CCL22 resulted in the opposite effects in CD4⁺ T cells from the healthy control. STAT5 inhibitor significantly reversed the effects of anti-CCL22 antibody. Similarly, sinomenine, an anti-arthritis drug, which decreased CCL22 and CCR4, showed the same trends as the above events, and was reversed by recombinant CCL22 or STAT5 inhibitor. Collectively, anti-CCL22 induced the number of Tregs via STAT5 pathway, leading to expansion of Tregs and subsequently to control of the autoimmune reaction in RA patients. Our study provides s novel strategy for RA treatment.

Dysfunctional and Proinflammatory Regulatory T-Lymphocytes Are Essential for Adverse Cardiac Remodeling in Ischemic Cardiomyopathy

BACKGROUND

Heart failure (HF) is a state of inappropriately sustained inflammation, suggesting the loss of normal immunosuppressive mechanisms. Regulatory T-lymphocytes (Tregs) are considered key suppressors of immune responses; however, their role in HF is unknown. We hypothesized that Tregs are dysfunctional in ischemic cardiomyopathy and HF, and they promote immune activation and left ventricular (LV) remodeling.

METHODS

Adult male wild-type C57BL/6 mice, Foxp3-diphtheria toxin receptor transgenic mice, and tumor necrosis factor (TNF) α receptor-1 (TNFR1)^-/- mice underwent nonreperfused myocardial infarction to induce HF or sham operation. LV remodeling was assessed by echocardiography as well as histological and molecular phenotyping. Alterations in Treg profile and function were examined by flow cytometry, immunostaining, and in vitro cell assays.

RESULTS

Compared with wild-type sham mice, CD4⁺Foxp3⁺ Tregs in wild-type HF mice robustly expanded in the heart, circulation, spleen, and lymph nodes in a phasic manner after myocardial infarction, beyond the early phase of wound healing, and exhibited proinflammatory T helper 1-type features with interferon-γ, TNFα, and TNFR1 expression, loss of immunomodulatory capacity, heightened proliferation, and potentiated antiangiogenic and profibrotic properties. Selective Treg ablation in Foxp3-diphtheria toxin receptor mice with ischemic cardiomyopathy reversed LV remodeling and dysfunction, alleviating hypertrophy and fibrosis, while suppressing circulating CD4⁺ T cells and systemic inflammation and enhancing tissue neovascularization. Tregs reconstituted after ablation exhibited restoration of immunosuppressive capacity and normalized TNFR1 expression. Treg dysfunction was also tightly coupled to Treg-endothelial cell contact- and TNFR1-dependent inhibition of angiogenesis and the mobilization and tissue infiltration of CD34⁺Flk1⁺ circulating angiogenic cells in a C-C chemokine ligand 5/C-C chemokine receptor 5-dependent manner. Anti-CD25-mediated Treg depletion in wild-type mice imparted similar benefits on LV remodeling, circulating angiogenic cells, and tissue neovascularization.

CONCLUSIONS

Proinflammatory and antiangiogenic Tregs play an essential pathogenetic role in chronic ischemic HF to promote immune activation and pathological LV remodeling. The restoration of normal Treg function may be a viable approach to therapeutic immunomodulation in this disease.

Replenishing Regulatory T Cells to Halt Depigmentation in Vitiligo

Vitiligo is a cutaneous autoimmune disease, especially devastating to patients with darker skin tones because of the contrast between unaffected and lesional skin. We studied immune cells infiltrating vitiligo skin and found very few regulatory T cells (Tregs). Vitiligo was not associated with a reduced frequency or function of circulating Tregs. To manipulate Treg function, we used mouse models expressing melanocyte-reactive TCRs, following changes in pelage color. We also isolated splenocytes to measure Treg function and evaluated cutaneous Treg abundance. Even small numbers of Tregs transferred into depigmenting mice could effectively interfere with depigmentation. The same holds true for treatment with rapamycin, readily translatable for use in human patients; such treatment may be well tolerated. Because vitiligo skin is relatively devoid of cells that produce the chemokine CCL22, whereas circulating Tregs express normal levels of its receptor CCR4, we overexpressed Ccl22 in the skin of vitiligo-prone mice to assess the resulting levels of depigmentation. Markedly reduced depigmentation was accompanied by Treg infiltration to the skin. With several options available to support a healthy balance between Tregs and effector T cells, the next challenge will be to render such treatment antigen specific and avoid general immunosuppression.