Search results
Results from the WOW.Com Content Network
Type III hypersensitivity, in the Gell and Coombs classification of allergic reactions, occurs when there is accumulation of immune complexes (antigen-antibody complexes) that have not been adequately cleared by innate immune cells, giving rise to an inflammatory response and attraction of leukocytes.
Since antigen levels are usually low, contact in blood circulation would be unlikely. Therefore, T cells need a region where they can go to sample foreign antigens that have entered the body. When an APC, such as a dendritic cell, binds a foreign antigen, it becomes activated and moves into the lymph nodes (sites for antigen sampling by T cells ...
An illustration that shows how antigens induce the immune system response by interacting with an antibody that matches the molecular structure of an antigen. In immunology, an antigen (Ag) is a molecule, moiety, foreign particulate matter, or an allergen, such as pollen, that can bind to a specific antibody or T-cell receptor. [1]
If the individual has circulating antibody either from passive immunity or because of prior encounter with the antigen, an Arthus reaction may occur. Typical of most mechanisms of the type III hypersensitivity , Arthus manifests as local vasculitis due to deposition of IgG-based immune complexes in dermal blood vessels.
There are three compartments involved in this antigen presentation pathway: early endosomes, late endosomes or endolysosomes, and lysosomes, where antigens are hydrolized by lysosome-associated enzymes (acid-dependent hydrolases, glycosidases, proteases, lipases). This process is favored by gradual reduction of the pH.
For example, they are important as antigen presenters to T cells. In humans, dysfunctional macrophages cause severe diseases such as chronic granulomatous disease that result in frequent infections. Beyond increasing inflammation and stimulating the immune system, macrophages also play an important anti-inflammatory role and can decrease immune ...
In contrast, the B cell antigen-specific receptor is an antibody molecule on the B cell surface and recognizes native (unprocessed) antigen without any need for antigen processing. Such antigens may be large molecules found on the surfaces of pathogens, but can also be small haptens (such as penicillin) attached to carrier molecule. [60]
Henoch–Schönlein purpura (HSP) is a systemic vasculitis caused by deposits of IgA and complement component 3 (C3) in small blood vessels. HSP occurs usually in small children and involves the skin and connective tissues, scrotum, joints, gastrointestinal tract and kidneys.