Mast cells functional consequences

IL-10 causes the inhibition of general proinflammatory cytokine synthesis, APC function, and cell-mediated immunity and induces the terminal differentiation of B cells into plasmacytes, which results in production of antibodies. Consequently, it has important effects on T and B lymphocytes, NK cells, monocytes and/or macrophages, and mast cells. It is characterized by a paradoxical duality of function (negative and/or positive Box 22-5). 

The most important functional abnormality in asthma is increased resistance to airflow. This is the basis of most striking clinical manifestation of asthma, including breathlessness and wheezing. The mechanisms of increased airflow resistance include (1) decreased physical dimensions of the airways as a consequence of bronchoconstriction, (2) luminal narrowing due to airway wall edema, and (3) luminal obstruction resulting from h)q)ersecretion of mucus (McFadden, 1998). Those changes induced by the various inflammatory mediators released by mast cells as part of hypersensitivity reactions are reversible. Another functional abnormality... 

In 1996 the exosome was discovered to have an immunological function and consequent study of the immunological role of exosomes has been extensive (Raposo et al., 1996). Exosomes have been shown to take part in both T-cell activation (Sprent, 2005) and in tolerance development (Karlsson et al., 2001). It has been shown that exosomes released from mast cells have the capacity to activate T cells and endothelial cells, and in addition to induce DC maturation. Thus, there is now extensive evidence that exosomes can mediate communication between cells over a distance. Furthermore, exosomes primed with specific tumor antigens are under clinical trials for cancer treatment. 

One question that has never been properly answered is What is the biological function of CVF in cobra venom Cobra venom factor in purified form can be considered nontoxic. When introduced into the bloodstream of an animal, complement activation with consumption of complement component occurs (41). Intravascular complement activation may have some side effects, such as sequestration of neutrophils to the lungs with subsequent injury to lung tissue (42). However, unless massive amounts of CVF are administered i.v., the consequences of intravascular complement activation by CVF are insignificant compared with the toxic effects of the other venom components, particularly the neurotoxins and membrane toxins. It appears, therefore, that local complement activation at the site of venom injection into the prey animal may be the beneficial effect of CVF for the cobra. Local complement activation by CVF will release the anaphylatoxins C3a and C5a which, in turn, will cause the degranulation of mast cells and basophils, with subsequent increase of the vascular permeability. The increased vascular permeability locally at the site of venom... 

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