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Antigenic variation can result from gene conversion, [1] site-specific DNA inversions, [2] hypermutation, [3] or recombination of sequence cassettes. [4] The result is that even a clonal population of pathogens expresses a heterogeneous phenotype. [5] Many of the proteins known to show antigenic or phase variation are related to virulence. [6]
(A) An early schizont with cluster of knobs at the center. Scale bar = 1 μm. Inset is the same image under light microscope. (B) A young trophozoite with knobs. Scale bar = 1 μm. (C) A close up of the cell membrane showing individual knobs. Scale bar = 200 nm. (D) A close up of a single knob. Scale bar = 75 nm. [1]
IgG3 is an efficient activator of pro-inflammatory responses by triggering the classical complement pathway. [10] It has the shortest half-life compared to the other IgG subclasses [11] and is frequently present together with IgG1 in response to protein antigens after viral infections. [12]
The human immune system relies on a plethora of cell-cell signaling pathways to transmit information about a cell's health and microenvironment. Many of these pathways are mediated by soluble ligands, cytokines, that fit like a lock-and-key into adjacent cell surface receptors.
Class switching occurs after activation of a mature B cell via its membrane-bound antibody molecule (or B cell receptor) to generate the different classes of antibody, all with the same variable domains as the original antibody generated in the immature B cell during the process of V(D)J recombination, but possessing distinct constant domains in their heavy chains.
As a consequence, external soluble antigens are targeted into the MHC class I cross-presentation pathway instead of the MHC Class II pathway. [citation needed] However, there is still uncertainty in regard to a mechanistic pathway for cross presentation within an antigen presenting cell. Currently, there are two main pathways proposed ...
This process involves two distinct pathways for processing of antigens from an organism's own (self) proteins or intracellular pathogens (e.g. viruses), or from phagocytosed pathogens (e.g. bacteria); subsequent presentation of these antigens on class I or class II major histocompatibility complex (MHC) molecules is dependent on which pathway ...
1) A hematopoietic stem cell undergoes differentiation and genetic rearrangement to produce 2) immature lymphocytes with many different antigen receptors. Those that bind to 3) antigens from the body's own tissues are destroyed, while the rest mature into 4) inactive lymphocytes. Most of these never encounter a matching