A pharmaceutical composition includes a physiologically active conjugate including a Thymosin alpha 1 (TA1) peptide conjugated to a material which increases half-life of the TA1 peptide in serum of a patient when the conjugate is administered to a patient. The material may be a substantially non-antigenic polymer. In a method of the invention, the substantially non-antigenic polymer is conjugated to a TA1 peptide. Compositions according to the invention are administered to patients in need of immune stimulation.
