CD4 and type 1 diabetes mellitus: Other experimental T cell immunotherapies include abatacept (cytotoxic T-lymphocyte associated protein 4 [CTLA4]-Ig), which limits T cell activation by blocking CD28 interaction with costimulatory molecules and preserves C-peptide levels in individuals with recent-onset type 1 diabetes [27], and anti-thymocyte globulin (ATG) [28, 29], which increases the ratio of CD4+ regulatory T cells (Treg) to CD4+ conventional T cells (Tconv) and promotes CD4+ T cell exhaustion.