Irradiation of fibroblasts from these SCID pigs and normal controls showed that the genetic defect is in the group of genes involved in DNA damage repair. Quantitative real-time PCR (qRT-PCR) and flow cytometry assays confirmed that the SCID pigs lack B and T cells, but do have NK cells we also demonstrate T cell maturation defects in the thymus. In this study, to our knowledge we present the first report of the characterization of the genetic lesions that cause the SCID phenotype in this pig population. ( 22) reported minimal circulating B and T cells but normal amounts of NK cells in a preliminary analysis of these SCID pigs. In subsequent work, we ( 21) demonstrated that these immunodeficient pigs failed to reject human cancer cells, and Ewen et al. Necropsy of four piglets that died abnormally early in a viral challenge study showed that they lacked functional adaptive immune systems. Recently, our group ( 19) reported, to our knowledge, the first identification of a naturally occurring form of SCID in a line of purebred Yorkshire pigs that had been selected for increased feed efficiency at Iowa State University ( 20). Recently, transgenic methods have been used to create SCID pigs, including mutations in the X-linked IL2RG gene ( 15, 16) and mutations in RAG1 or in both RAG1 and RAG2 ( 17, 18). The identified mutations and associated genetic tests can be used to address both of these issues.Īnatomical, genetic, and immunological similarities underpin the usefulness of swine as a large animal model for humans ( 13, 14). The SCID pig can be an important biomedical model, but these mutations would be undesirable in commercial pig populations. The work presented in the present study reveals two mutations in the Artemis gene that cause T −B −NK + SCID in pigs. Rescue of SCID fibroblast radiosensitivity by human Artemis protein demonstrated that the identified Artemis mutations are the direct cause of this cellular phenotype. Genetic and molecular analyses showed that two mutations were present in the Artemis gene, which in the homozygous or compound heterozygous state cause the immunodeficient phenotype. Fibroblasts from these pigs were more sensitive to ionizing radiation than non-SCID piglets, eliminating the RAG1 and RAG2 genes. Flow cytometry analysis of thymocytes showed an increased frequency of immature T cells in SCID pigs. In this study, we present evidence for two spontaneous mutations as the molecular basis for this SCID phenotype. Piglets from a line of Yorkshire pigs at Iowa State University were shown to be affected by T −B −NK + SCID, representing, to our knowledge, the first example of naturally occurring SCID in pigs. SCID disorders are split into groups based on their presence and/or functionality of B, T, and NK cells. Mutations in >30 genes are known to result in impairment of the adaptive immune system, causing a group of disorders collectively known as SCID.
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