CD8⁺ T Cell Phenotype and Function in Childhood and Adult-Onset Connective Tissue Disease

CD8⁺ T cells are cytotoxic lymphocytes that destroy pathogen infected and malignant cells through release of cytolytic molecules and proinflammatory cytokines. Although the role of CD8⁺ T cells in connective tissue diseases (CTDs) has not been explored as thoroughly as that of other immune cells, research focusing on this key component of the immune system has recently gained momentum. Aberrations in cytotoxic cell function may have implications in triggering autoimmunity and may promote tissue damage leading to exacerbation of disease. In this comprehensive review of current literature, we examine the role of CD8⁺ T cells in systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, polymyositis, and dermatomyositis with specific focus on comparing what is known about CD8⁺ T cell peripheral blood phenotypes, CD8⁺ T cell function, and CD8⁺ T cell organ-specific profiles in adult and juvenile forms of these disorders. Although, the precise role of CD8⁺ T cells in the initiation of autoimmunity and disease progression remains to be elucidated, increasing evidence indicates that CD8⁺ T cells are emerging as an attractive target for therapy in CTDs.