1) The crystal structure of a murine T-cell receptor alpha-chain variable domain has been determined and refinement is in progress. 2) Single-chain Fv fragments of anti-tumor antibodies, linked to human Fc, have been engineered to form multivalent and multispecific molecules. 3) Small crystals have been obtained for the Fab of a polyreactive murine antibody. 4) Small crystals have been obtained for the Fab of a second human autoantibody that binds to thyroid peroxidase. 5) Sequence analysis is being performed to help in the understanding of the structural basis for the affinity maturation of antibodies.