Distinct roles of helper T-cell subsets in a systemic autoimmune disease.

Imbalance of T-helper cell (Th) differentiation and subsequent cytokine dysregulation is implicated in inflammatory and autoimmune diseases. In particular, 2 cytokines produced by different Th cell populations, interferon-gamma (IFN-gamma) and interleukin-17 (IL-17), have been shown to play a critical role in autoimmunity. We have examined the roles of these cytokines in a mouse model of systemic autoimmunity resulting from the deletion of IL-2 in which autoimmune hemolytic anemia (AIHA) is a prominent feature. We demonstrate that, in IL-2-knockout (KO) BALB/c mice, elimination of the Th1 cytokine, IFN-gamma, delays the development of AIHA. Further, CD4(+) T cells from IL-2/IFN-gamma-KO mice produce elevated levels of IL-17 compared with wild-type (WT) and IL-2-KO, and these mice eventually develop intestinal inflammation. In contrast, elimination of the Th17 cytokine, IL-17, from IL-2-KO mice fails to suppress early acute AIHA development. These results suggest that in a systemic autoimmune disease with multiple manifestations, Th1 cells drive the early autoantibody response and IL-17-producing cells may be responsible for the more chronic tissue inflammation.

The initial phase of an immune response functions to activate regulatory T cells.

An early reaction of CD4(+) T lymphocytes to Ag is the production of cytokines, notably IL-2. To detect cytokine-dependent responses, naive Ag-specific T cells were stimulated in vivo and the presence of phosphorylated STAT5 molecules was used to identify the cell populations responding to IL-2. Within hours of T cell priming, IL-2-dependent STAT5 phosphorylation occurred primarily in Foxp3(+) regulatory T cells. In contrast, the Ag-specific T cells received STAT5 signals only after repeated Ag exposure or memory differentiation. Regulatory T cells receiving IL-2 signals proliferated and developed enhanced suppressive activity. These results indicate that one of the earliest events in a T cell response is the activation of endogenous regulatory cells, potentially to prevent autoimmunity.

Rheumatologic symptoms in oncologic patients on PD-1 inhibitors.

OBJECTIVE: Immune checkpoint inhibitors are effective cancer therapies that have been associated with immune-related adverse events (irAEs). Recent reports of irAEs describe symptoms resembling classic rheumatologic syndromes, most notably associated with cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) inhibitor blockade. Though cases have been described, there are fewer reports of rheumatologic disease associated with programmed cell death protein-1 (PD-1) inhibitors. Here, we describe a series of four patients presenting to the Brigham and Women's Hospital (BWH) Arthritis Center with de novo polymyalgia rheumatica (PMR)-type conditions and/or peripheral synovitis after treatment with PD-1/PD-Ligand 1 (PD-L1) pathway inhibitors. METHODS: Patients with metastatic renal cell carcinoma (RCC) who were treated with PD-1/PD-L1 pathway inhibitors and subsequently developed complaints of new joint pain were referred to the BWH Arthritis Center as part of routine care and identified retrospectively. The electronic medical record was reviewed for cancer history and treatment, rheumatologic symptoms, physical exam, laboratory testing, and clinical course. RESULTS: All four patients developed irAEs consistent with a PMR-type syndrome and/or peripheral synovitis. Symptoms persisted despite discontinuation of the PD-1/PD-L1 pathway inhibitors; however, three of the patients responded well to oral glucocorticoids alone while one patient required the addition of oral methotrexate. All patients had an eventual decline in inflammatory markers. CONCLUSION: These cases highlight the need for both oncologists and rheumatologists to recognize the development of rheumatologic disease during treatment with immune checkpoint blockade. Further investigation is needed to optimize the management of irAEs, particularly considering the increasing use of checkpoint inhibitors to treat malignancies.