Compositions and methods useful in modulating the innate and adaptive immune systems in a subject, including activation of natural killer (NK) cells and/or CD8+ cytotoxic T lymphocytes. The method typically comprises: administering to the subject a composition comprising a therapeutic peptide or a multivalent structured polypeptide comprising multiple copies of the therapeutic peptide described herein in an amount sufficient to increase activity of NK cells and/or CD8+ cytotoxic T lymphocytes in the subject. Preferred therapeutic compositions comprise a carrier at least one agent selected from the group consisting of: an anti-inflammatory agent, a cytotoxic T cell proliferation agent, or a NK cell proliferation agent and a therapeutic peptide or a multivalent structured polypeptides of the invention. In certain embodiments, the composition further comprises an immunoglobulin admixed therewith in an amount sufficient to enhance passive immunoprotection in the subject. In other embodiments, the compositions are administered in a therapeutically effective amount to a subject in need thereof to treat rheumatoid arthritis.
