No abstract

During the assembly of immunoglobulin and T cell receptor variable region genes from variable (V), diversity (D), and joining (J) segments, the germline-encoded repertoire is further diversified by processes that include the template-independent addition of nucleotides (N regions) at gene segment junctions. Terminal deoxynucleotidyl transferase (TdT)-deficient lymphocytes had no N regions in their variable region genes, which shows that TdT is responsible for N region addition. In addition, certain variable region genes appeared at increased frequency in TdT-deficient thymocytes, which indicates that N region addition also influences repertoire development by alleviating sequence-specific constraints imposed on the joining of particular V, D, and J segments.

We describe a system to evaluate the function of lymphocyte-specific and generafly expressed genes in the differentiation and/or function of lymphocytes. RAG-2 (recombination-activating gene 2)-deficient mice have no mature B and T lymphocytes due to the inability to initiate VDJ recombination. Blastocysts from RAG-2-deficient mice generate animals with no mature B and T cells foOlowing implantation into foster mothers. However, i 'ection of normal ES