SOCS1 prevents potentially skin-reactive cytotoxic t lymphocytes from gaining the ability to cause inflammatory lesions

Abstract

Suppressor of cytokine signaling 1 (SOCS1) is a critical regulator of T lymphocyte homeostasis. SOCS1-deficient mice accumulate CD8+ T cells, which display a memory-like phenotype and proliferate strongly to IL-15. Socs1 -/- mice develop inflammatory skin lesions, however, the underlying mechanisms are not well understood. In order to investigate the role of SOCS1 in regulating CD8+ T cells potentially reactive to tissue antigens (Ags) of the skin, we generated Socs1 -/- mice expressing MHC-I-restricted Pmel-1 transgenic TCR specific to the melanoma-derived gp100 Ag, which is also expressed by normal melanocytes. Socs1 -/- Pmel-1 cells express increased levels of memory markers CD44, Ly6C, CD122, and CD62L, and show downregulation of TCR and upregulation of CD5, suggesting in vivo TCR stimulation. However, stimulation of Socs1 -/- Pmel-1 cells with gp100-derived peptide induced only marginal proliferation in vitro despite eliciting strong effector functions, which was associated with elevated Blimp-1 induction. Following adoptive transfer to Rag1 -/- mice, Socs1 -/- Pmel-1 cells underwent lymphopenia-induced proliferation and caused severe skin pathology characterized by inflammatory lesions in ears, muzzle, extremities, and eyes. These findings underscore the importance of SOCS1 in regulating potentially skin-reactive cytotoxic T lymphocytes, which could get activated under conditions that promote Ag-nonspecific, cytokine-driven proliferation. © 2013 The Society for Investigative Dermatology.