Abstract <p>This review summarizes recent progress in the engineering of monoclonal antibodies directed to a variable fragment of the T-cell receptor with a given mode of action on the targeted subset of T lymphocytes. Since the unique T-cell subsets are responsible for the development and outcome of many socially significant diseases, the ability of monoclonal antibodies to deplete or expand pathogenetically important T-cell families is of a great interest in clinical practice. The review also discusses the role of the unique T-cell families in the pathogenesis of a number of autoimmune and infectious diseases, which provides the prerequisites for the creation of highly effective targeted drugs on the basis of monoclonal antibodies to a variable fragment of the T-cell receptor.</p>