In alternative embodiments, provided are compositions, including e.g., isolated, synthetic or recombinant peptides or polypeptides, for: expanding regulatory T cells (Treg) populations； or, for treating, ameliorating, preventing or reversing a vascular inflammation, and Kawasaki disease (KD) or a pediatric acute vasculitis of the coronary arteries, including vascular coronary abnormalities and the same or similar types of acute or chronic vascular inflammatory abnormalities, and methods for making and using them. In one embodiment, provided are immunotherapies for promoting expansion of natural, regulatory T cells to establish, or re-establish, vascular homeostasis； or, for treating, reversing, preventing or ameliorating: a disease or condition associated with an autoimmune disease or condition； an immune-mediated vascular disorder； a disease or condition that is currently treated with intravenous immunoglobulin (IVIG) therapy； a vascular coronary abnormality； an acute or a chronic vasculitis； an autoimmune inflammatory vasculitis； a T cell mediated pediatric vasculitis； Kawasaki disease (KD) or a pediatric acute vasculitis of the coronary arteries； atherosclerosis； rheumatoid arthritis or Juvenile Idiopathic Arthritis； an autoimmune disease or condition； or, a neoplastic hematological disorder such as a lymphoma (e.g., a T cell lymphoma) or a leukemia.
