An antigen-presenting cell APC is an immune cell that detects, engulfs, and informs the adaptive immune response about an infection. When a pathogen is detected, these APCs will phagocytose the pathogen and digest it to form many different fragments of the antigen.
Antigen fragments will then be transported to the surface of the APC, where they will serve as an indicator to other immune cells. Dendritic cells are immune cells that process antigen material; they are present in the skin Langerhans cells and the lining of the nose, lungs, stomach, and intestines. Sometimes a dendritic cell presents on the surface of other cells to induce an immune response, thus functioning as an antigen-presenting cell.
Macrophages also function as APCs. Before activation and differentiation, B cells can also function as APCs. The key role of segmented filamentous bacteria in the coordinated maturation of gut helper T cell responses.
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J Immunol Methods. Mice lacking T and B lymphocytes develop transient colitis and crypt hyperplasia yet suffer impaired bacterial clearance during Citrobacter rodentium infection.
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Clin Cancer Res. Dendritic cell-based cancer immunotherapy for colorectal cancer. Waldmann TA. The shared and contrasting roles of IL2 and IL15 in the life and death of normal and neoplastic lymphocytes: implications for cancer therapy. Cancer Immunol Res. Without peptides, these molecules are stabilised by chaperone proteins : calreticulin, Erp57, protein disulfide isomerase PDI and tapasin. Tapasin interacts with the transport protein TAP transporter associated with antigen presentation which translocates peptides from the cytoplasm into the ER.
Prior to entering the ER, peptides are derived from the degradation of proteins, which can be of viral- or self origin. Degradation of proteins is mediated by cytosolic- and nuclear proteasomes, and the resulting peptides are translocated into the ER by means of TAP.
This process allows viral peptides to be presented very quickly — for example, influenza virus can be recognised by T cells approximately 1.
In some cases, peptides fail to associate with MHC class I and they have to be returned to the cytosol for degradation.
There are different proteasomes that generate peptides for MHC class-I presentation: 26S proteasome , which is expressed by most cells; the immunoproteasome, which is expressed by many immune cells; and the thymic-specific proteasome expressed by thymic epithelial cells. On the surface of a single cell, MHC class I molecules provide a readout of the expression level of up to 10, proteins. Research 18 October Open Access. Ko-Han Lee et al. They demonstrate that MHCfovea is capable of detecting meaningful hyper-motifs and allele signatures, making it a useful resource for the community.
Reviews 11 October Chong et al. Research 05 October Open Access. The maintenance of T resident memory T RM cells within pulmonary tissues is incompletely understood. Here the authors show that antigen presentation by lung epithelial cells maintains function and phenotype of pulmonary T RM cells within specific locational niches.
Research Highlights 17 September A new study explores the links between diet and colorectal cancer risk by showing that changes to the intestinal microbiome in mice fed a high-fat diet result in attenuated MHC class II expression by intestinal stem cells and hence impaired immune surveillance of tumour initiation.
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