Further refinement has been continued on McPC603 Fab, a murine phosphocholine specific myeloma protein. The structure of the murine galactan-specific J539Fab has been solved and refinement has been commenced. Attempts are underway to crystallize various histocompatibility antigens as well as a number of hybridoma immunoglobulin Fab fragments specific for lysozyme, myoglobin and certain oligosaccharides.