Antibody polypeptides that specifically bind a novel epitope of human CD40 are provided. The antibody polypeptides do not exhibit CD40 agonist activity. The antibody polypeptides are useful in the treatment of diseases involving CD40 activation, such as autoimmune diseases. The antibody polypeptides may be domain antibodies (dAbs) comprising a single V L or V H domain. The half-life of the antibody polypeptides may be increased by modifying the antibody polypeptides to be dual specific reagents that can also bind human serum albumin (HSA).
