1) Crystals of TSST-1 of S. aureus, the major toxin in Toxic Shock Syndrome, have been obtained. 2) Crystals of the Fab of CC49, a murine monoclonal antibody against solid adenocarcinomas, have been obtained. 3) A possible procedure for the 'humanization' of xenogeneic antibodies has been developed as an alternative to CDR-grafting. 4) A model of the Fc of human IgE, that incorporates the recently deduced inter epsilon chain disulfide linkage, has been built. 5) The preferred reading frames in the expression of the D regions of immunoglobulin heavy chains and of the T-cell receptor beta-chains have been analyzed and correlated with possible structural constraints.