Connective tissue diseases (or systemic autoimmune diseases), such as rheumatoid arthritis or systemic lupus erythematosus, are characterized by B cell hyperactivity and production of various autoantibodies. T cells help B cell activation in the germinal center by enhancing somatic hypermutation and generation of high affinity pathogenic autoantibodies. Previously helper T cells were divided into Th-1 and Th-2 cells. Recently, Th-17 cells and regulatory T cells have been identified as distinct T cell lineages and their roles in inflammation or immune regulation are under intensive investigation. In this review, we discuss the contribution of each T cell subset to autoantibody production and systemic autoimmune diseases.