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Studies of the sites and mechanisms for the diversification and development of the B cell repertoire in cattle
Studies were undertaken to examine immunoglobulin repertoire diversification in cattle. Diversification was examined in a number of organs from late first trimester bovine fetuses and from the ileal Peyer’s patch (IPP) follicles of young calves. To investigate the diversification in IPP follicles, individual IPP follicles were isolated by microdissection and diversification of the lambda variable region was examined by RT-PCR and subsequent cloning and sequencing. When intrafollicular sequences from a 4 week old calf were determined and compared, two major groups could be delineated. An examination of these groups revealed clear genealogical relationships that implicated both gene conversion and untemplated somatic hypermutation as the mechanisms responsible for diversification of VX within the IPP follicles. Diversification of Vλ was also examined in early (95–110 gestational day) fetal organs. The organs examined included fetal spleen, blood, liver, thymus, ileum and bone marrow. Sequences obtained from the various organs revealed that while Vλ sequences were highly diversified in spleen, very little VλX diversification was seen in the blood, liver, ileum or bone marrow. The sequences obtained from spleen indicated that both gene conversion and untemplated somatic hypermutation could be taking place in fetal spleen. Evidence for diversification in fetal spleen was also obtained by examining expression of recombination activating genes (RAG). An examination of fetal tissues for the expression of RAG-1 found that RAG-1 transcripts were present only in fetal thymus, bone marrow and spleen. The presence of both RAG-1 transcripts and a highly diversified population of Vλ sequences implicates the fetal spleen as an organ where both Vλ rearrangement and diversification might take place in cattle.
Veterinary services|Cellular biology|Immunology|Genetics
Lucier, Mark R, "Studies of the sites and mechanisms for the diversification and development of the B cell repertoire in cattle" (1999). Doctoral Dissertations Available from Proquest. AAI9920626.