Abstract: This invention relates to methods of preventing or reducing the severity of diabetes. In one embodiment, the method involves administering to the individual a peptide having substantially the sequence of a on-conserved region sequence of a T cell receptor present on the surface of T cells mediating diabetes or a fragment thereof, wherein the peptide or fragment is capable of causing an effect on the immune system to regulate the T cells. In particular, the T cell receptor has the V.beta. regional V.beta.6 or V.beta.14. In another embodiment, the method involves gene therapy. The invention also relates to methods of diagnosing diabetes by determining the presence of diabetes predominant T cell receptors.

Abstract: This invention provides methods for identifying lymphocytes with a mutator phenotype by isolating lymphocytes bearing a selectable marker; identifying among the lymphocytes a population belonging to the same clonally amplified set; and determining whether the population has at least two lymphocytes having, between them, two independent mutations among different alleles at the gene locus of the selectable marker; the presence of which indicates a mutator phenotype. In one embodiment of the invention, the selectable marker is hprt.sup.-.

Abstract: A method for detecting lymphocyte clonal amplification in a mammal by cloning of lymphocytes so as to identify cell lines expressing a mutation at a structural locus and determining the structure of the antigen receptor in the mutated clonal cell lines. Similar rearrangements of the regions of nucleic acid encoding antigen receptor among multiple isolated clones from a single individual indicate an in vivo clonal lymphocyte amplification event.