Citrullinated peptide presentation by DCs and macrophages is constitutive, whereas B cells present modified peptides only with autophagy induced by serum starvation or BCR ligation.
Abs against citrullinated proteins are present in patients with rheumatoid arthritis. In this study, we describe a unique cohort of T cells that selectively responded to citrullinated variants of two epitopes of hen egg-white lysozyme, a major and a minor one, bound to the MHC molecule, I-Ak. In addition, we show that when given an intact, unmodified lysozyme protein, dendritic cells and peritoneal macrophages presented citrullinated peptides and stimulated modification-specific T cells. Thus, presentation of citrullinated-peptide-MHC complex is a feature of immune responses to protein Ags.
This is the first study to characterize the environmental conditions which contribute to the presence and proliferation of environmental mycobacteria in a major freshwater river. Over 20 different species of environmental mycobacteria were isolated, including the pathogenic M. avium and M. kansasii. Species of the rapidly growing M. fortuitum complex were the most commonly isolated mycobacteria, and one-third of all isolates were not identified at the species level, even by 16S sequencing. PCR restriction analysis of the hsp65 gene was more accurate and rapid than biochemical tests and as accurate as yet less expensive than 16S sequencing, showing great promise as a new tool for species identification of environmentally isolated mycobacteria. Total environmental mycobacteria counts positively correlated with coliform and Escherichia coli counts and negatively correlated with chemical toxicity and water temperature. Environmental mycobacteria can survive in the alkaline conditions of the river despite previous reports that especially acidic conditions favor their presence. A representative river isolate (M. fortuitum) survived better than E. coli O157:H7 at pHs below 7 and above 8 in nutrient broth. The river strain also retained viability at 8 ppm of free chlorine, while E. coli was eliminated at 2 ppm and above. Thus, in vitro studies support environmental observations that a variety of extreme conditions favor the hardy environmental mycobacteria.
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