The studies on the development of the B cell lineage will be extended to the markers Lyb3, Lyb4 and Lyb6. The main technique to be used will be the induction assay, which will be applied in conjunction with immunoselection procedures and which will allow us to determine the surface phenotype of each inducible cell. The information gained from such experiments will be used to construct a sequence of lymphocyte developmental stages. By application of the technique developed by Kohler and Milstein, a number of hybridomas with specificity to Ia antigens, subregions AB, E and C have been developed. We will develop further monoclonal antibodies to Lyb2 and Lyb5. Abundance of antibody of assured specificity will allow us to develop new techniques to study the induction phenomenon. We plan to directly fluoresceinate anti-Ia antibodies and monitor induction in the fluorescence activated cell sorter.