The present invention relates to methods for the prevention and/or treatment of cardiovascular and allergic diseases and disorders, methods for inhibiting the growth of, or reducing the volume of, a solid tumor, as well as methods for preventing progression to AIDS in an HIV-infected human, by administering a peptide derived from T cell receptors, or a derivative thereof. The present invention also relates to peptides derived from T-cell receptors, and derivatives thereof, which are useful in such methods.