<P> Most T cell receptors are composed of an alpha chain and a beta chain . The T cell receptor genes are similar to immunoglobulin genes in that they too contain multiple V, D and J gene segments in their beta chains (and V and J gene segments in their alpha chains) that are rearranged during the development of the lymphocyte to provide that cell with a unique antigen receptor . The T cell receptor in this sense is the topological equivalent to an antigen - binding fragment of the antibody, both being part of the immunoglobulin superfamily . </P> <P> Failure of the cell to create a successful product that does not self - react leads to apoptosis . Autoimmunity is prevented by eliminating lymphocytes that self - react in the thymus by testing them against an array of self antigens expressed through the function of Aire . The immunoglobulin lambda light chain locus contains protein - coding genes that can be lost with its rearrangement . This is based on a physiological mechanism and is not pathogenetic for leukemias or lymphomas . </P> <P> In the developing B cell, the first recombination event to occur is between one D and one J gene segment of the heavy chain locus . Any DNA between these two gene segments is deleted . This D-J recombination is followed by the joining of one V gene segment, from a region upstream of the newly formed DJ complex, forming a rearranged VDJ gene segment . All other gene segments between V and D segments are now deleted from the cell's genome . Primary transcript (unspliced RNA) is generated containing the VDJ region of the heavy chain and both the constant mu and delta chains (C and C). (i.e. the primary transcript contains the segments: V-D-J-C - C). The primary RNA is processed to add a polyadenylated (poly - A) tail after the C chain and to remove sequence between the VDJ segment and this constant gene segment . Translation of this mRNA leads to the production of the Ig M heavy chain protein . </P> <P> The kappa (κ) and lambda (λ) chains of the immunoglobulin light chain loci rearrange in a very similar way, except that the light chains lack a D segment . In other words, the first step of recombination for the light chains involves the joining of the V and J chains to give a VJ complex before the addition of the constant chain gene during primary transcription . Translation of the spliced mRNA for either the kappa or lambda chains results in formation of the Ig κ or Ig λ light chain protein . The immunoglobulin lambda light chain locus contains protein - coding genes that can be lost with its rearrangement . This is based on a physiological mechanism and is not pathogenetic for leukemias or lymphomas . However, the rearrangement of several lambda variable subgenes can activate expression of an overlapping miRNA gene, which has consequences for gene expression regulation . </P>

Who discovered the somatic recombination of immunological receptor genes