Disclosed herein is a T-helper cell (“TH-GM” cell) that is regulated by IL-7/STAT5 and which secrete GM-CSF/IL-3. Also disclosed are methods and compositions for modulating TH-GM function for the treatment of, e.g., inflammatory disorders. Diagnostic and prognostic methods for specifically identifying TH-GM-mediated inflammatory disorders (e.g., rheumatoid arthritis), as distinct from and/or in addition to non-TH-GM-mediated (e.g., TNF-α-mediated) inflammatory disorders, are also provided.