Methods of identifying a subject having an autoimmune disease, such as Type 1 diabetes, as likely to respond to treatment with a tumor necrosis factor-alpha (TNF-α) receptor II activator, involving measuring CD8 protein density on the surface of autoreactive CD8+ T cells and identifying the subject as likely to respond to the treatment if the CD8 protein density is reduced relative to a reference CD8+ T cell. For Type 1 diabetes, the method may involve measuring C-peptide levels in an in vitro biological sample from the subject, identifying the subject as likely to respond to the treatment if the C-peptide levels are detectable, and identifying the subject as unlikely to respond to the treatment if the C-peptide levels are substantially undetectable. The invention also features pharmaceutical compositions of one or more TNFR2 activators for therapeutic use.
