IMMUNE SENESCENCE AUTOIMMUNITY AND AGING

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There is substantial evidence that the aging immune system undergoes a variety of changes in both T cell and B cell function. Characteristically, senescent immunity in the elderly show both aberrant responses to common non-self antigens as well as production of a number of anti-self autoantibodies, even among those individuals without overt autoimmune disease. These apparent changes in immunoglobulin production are no doubt multi-factorial, but studies into the immunoglobulin repertoire of B cells giving rise to them will answer several fundamental questions about that repertoire and its changes with age. Although a great deal has been learned about the organization and rearrangement of the immunoglobulin heavy chain variable region (VH) gene, the expression of individual genes has until now been difficult to analyze. We have studied the VH genes of two human anti-DNA antibodies and shown that oligonucleotide probes from the most variable part of the gene, the complementarity determining regions (CDR), detect a very limited number of genes and that combined information from two CDRs identify individual, single genes in both germline and expression studies. Preliminary studies have shown that some VH genes may be overexpressed as compared to others. The group of overexpressed genes was seen to be highly related(greater than 98% homology) to each other in both CDR and framework regions. We propose to expand these findings and apply these methods of study of V gene expression in answer to some of the following questions: (1) Does the immune repertoire differ in the older, senescent immune system as compared to that in a young individual, or even between older individuals with and without overt autoimmune disease? (2) Is the frequency of expression of individual VH genes correlated with the frequency of rearrangement in bone marrow or does selection plays a dominant role in the expressed repertoire of the three types of individuals under study? (3) What is the mechanism of overexpression of certain VH genes: is it due to a (large) family of closely-related germline genes or to preferential expression of a single germline gene.(4) Test whether 'natural' non-pathogenic autoantibodies in the elderly are encoded by highly conserved, frequently-expressed V genes while autoantibodies from older individuals with overt autoimmune disease are encoded by less well conserved or less frequently expressed V genes.