Histocompatibility antigens are directly involved in immune function. Immune development and communication are some of the process in which class I histocompatibility antigens (H-2) take part. An animal lacking these antigens has never been isolated. The goals of this project are: 1) the mutation of the beta-2 macroglobulin (beta-2M) gene by homologous recombination in mouse embryonal stem (ES) cells, 2) the introduction of the beta-2M mutant Es cell into a mouse embryo and the breeding of a chimera, 3) the selection for a mouse line lacking beta-2M, and 4) the study of the immune function of a mouse lacking beta-2M, a protein required for class I H-2 antigen expression. The technology for disrupting genes in mice is currently being developed; therefore, a major portion of the effort described in this proposal is directed towards applying this methodology. If the approach is successful, it will provide two functions 1) the establishment of a useful procedure that can be applied to the characterization of other genes, and 2) the development of a useful reagent - mice deficient in class I H-2 antigen expression. These mice should provide answers about the function of these molecules in the immune network and determine if class I antigens have a role outside the immune system. I am third-year fellow in the Hematology Division at the Brigham and Women's Hospital. My training has included laboratory experience in protein biochemistry before medical school. Since then, my experience has been in clinical training. I have spent the past year working in an environment that is ideal for developing expertise in the techniques of molecule biology. The Department of Genetics has the equipment necessary for mouse embryo manipulation, tissue culture, and recombinant DNA technology. A biopolymers lab is available for the synthesis of peptides and oligonucleotides. The guidance I have received has helped me to design approaches for undertaking this proposal. Our division also sponsors a journal club, lab meetings, and several lecture series, and my colleagues provide an exciting and stimulating environment for research.