Browsing by Subject "Major Histocompatibility Complex"

Now showing 1 - 3 of 3
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    Common genetic variation and the control of HIV-1 in humans.
    (PLoS Genet, 2009-12) Fellay, Jacques; Ge, Dongliang; Shianna, Kevin V; Colombo, Sara; Ledergerber, Bruno; Cirulli, Elizabeth T; Urban, Thomas J; Zhang, Kunlin; Gumbs, Curtis E; Smith, Jason P; Castagna, Antonella; Cozzi-Lepri, Alessandro; De Luca, Andrea; Easterbrook, Philippa; Günthard, Huldrych F; Mallal, Simon; Mussini, Cristina; Dalmau, Judith; Martinez-Picado, Javier; Miro, José M; Obel, Niels; Wolinsky, Steven M; Martinson, Jeremy J; Detels, Roger; Margolick, Joseph B; Jacobson, Lisa P; Descombes, Patrick; Antonarakis, Stylianos E; Beckmann, Jacques S; O'Brien, Stephen J; Letvin, Norman L; McMichael, Andrew J; Haynes, Barton F; Carrington, Mary; Feng, Sheng; Telenti, Amalio; Goldstein, David B; NIAID Center for HIV/AIDS Vaccine Immunology (CHAVI)
    To extend the understanding of host genetic determinants of HIV-1 control, we performed a genome-wide association study in a cohort of 2,554 infected Caucasian subjects. The study was powered to detect common genetic variants explaining down to 1.3% of the variability in viral load at set point. We provide overwhelming confirmation of three associations previously reported in a genome-wide study and show further independent effects of both common and rare variants in the Major Histocompatibility Complex region (MHC). We also examined the polymorphisms reported in previous candidate gene studies and fail to support a role for any variant outside of the MHC or the chemokine receptor cluster on chromosome 3. In addition, we evaluated functional variants, copy-number polymorphisms, epistatic interactions, and biological pathways. This study thus represents a comprehensive assessment of common human genetic variation in HIV-1 control in Caucasians.
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    Intercellular Protein Transfer from Thymocytes to Thymic Epithelial Cells.
    (PLoS One, 2016) Wang, Hong-Xia; Qiu, Yu-Rong; Zhong, Xiao-Ping
    Promiscuous expression of tissue restricted antigens (TRAs) in medullary thymic epithelial cells (mTECs) is crucial for negative selection of self-reactive T cells to establish central tolerance. Intercellular transfer of self-peptide-MHC complexes from mTECs to thymic dendritic cells (DCs) allows DCs to acquire TRAs, which in turn contributes to negative selection and regulatory T cell generation. However, mTECs are unlikely to express all TRAs, such as immunoglobulins generated only in B cells after somatic recombination, hyper-mutation, or class-switches. We report here that both mTECs and cortical TECs can efficiently acquire not only cell surface but also intracellular proteins from thymocytes. This reveals a previously unappreciated intercellular sharing of molecules from thymocytes to TECs, which may broaden the TRA inventory in mTECs for establishing a full spectrum of central tolerance.
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    Strong Selection at MHC in Mexicans since Admixture.
    (PLoS genetics, 2016-02-10) Zhou, Quan; Zhao, Liang; Guan, Yongtao
    Mexicans are a recent admixture of Amerindians, Europeans, and Africans. We performed local ancestry analysis of Mexican samples from two genome-wide association studies obtained from dbGaP, and discovered that at the MHC region Mexicans have excessive African ancestral alleles compared to the rest of the genome, which is the hallmark of recent selection for admixed samples. The estimated selection coefficients are 0.05 and 0.07 for two datasets, which put our finding among the strongest known selections observed in humans, namely, lactase selection in northern Europeans and sickle-cell trait in Africans. Using inaccurate Amerindian training samples was a major concern for the credibility of previously reported selection signals in Latinos. Taking advantage of the flexibility of our statistical model, we devised a model fitting technique that can learn Amerindian ancestral haplotype from the admixed samples, which allows us to infer local ancestries for Mexicans using only European and African training samples. The strong selection signal at the MHC remains without Amerindian training samples. Finally, we note that medical history studies suggest such a strong selection at MHC is plausible in Mexicans.