Respiratory tract immunity

Toxicants can injnre one or more specific organs in the body, which include the liver, kidney, respiratory tract, immune system, skin, nervons system, eye, reproductive, and cardiovascnlar systems. The nature of such toxicants and their effects are briefly discussed in the following sections ... 

Defensins are a group of antimicrobial and cytotoxic peptides made by immune cells. There are seven defensins in humans, six alpha-defensins and one beta-defensin, which are involved in the innate immune defense at the surface of epithelia from the respiratory tract, the intestinal tract or the urinary tract. 

Vitamin C status is supposed to play a role in immune function and to influence the progression of some chronic degenerative diseases like atherosclerosis, cancer, cataracts, and osteoporosis. The role of vitamin C in immune function, especially during common cold and upper respiratory tract infection, is the subject of lively debate. The exact mechanisms of action have not yet been fully elucidated, but the results of several trials point to a reduced duration and intensity of infections in subjects consuming high amounts of vitamin C (200-1000 mg/d). However, the incidence of common cold was not influenced significantly (24). 

This is an acute, non-invasive infectious disease associated with the upper respiratory tract (Chapter 4). The incubation period is fiom 2 to 5 days although the disease remains communicable for up to 4 weeks. A low molecular weight toxin is produced which affects myocardium, nervous and adrenal tissues. Death results in 3-5% of infected children. Diphtheria immunization protects by stimulating the production of an antitoxin. This antitoxin will protect against the disease but not against infection of the respiratory... 

The adamantane moiety is of medicinal chemical interest because of its inertness, compactness relative to lipid solubilizing character, and symmetry. Considerable interest, therefore, was engendered by the finding that amantadine (78) was active for the chemoprophylaxis of influenza A in man. There are not many useful chemotherapeutic agents available for the treatment of communicable viral infections, so this finding led to considerable molecular manipulation. The recent abrupt end of the National Influenza Immunization program of 1976 prompted a new look at the nonvaccine means for prophylaxis or treatment of respiratory tract infections due to influenza A, especially in that the well-known antigenic shift or drift of the virus obviates usefulness of the vaccine but not amantadine. 

A number of cells, including cytotoxic T lymphocytes, NK cells, and mononuclear phagocytic cells, are endowed with cytotoxic abilities and thus mediate important immunosurveillance mechanisms against neoplastic cells and viral infections. In immune-compromised hosts, a correlation has been observed between low NK cell activity and morbidity [22-25] or the incidence and severity of upper respiratory tract infections [24],... 

Mechanisms underlying non-IgE mediated food allergy include immune complex formation and activation of lymphocytes. As with IgE-mediated responses, manifestations can be in the skin, gut, or respiratory tract however, these reactions take several hours to days to develop [65],... 

Respiratory hypersensitivity is an adverse reaction in the respiratory tract driven by immune mechanisms such as IgE antibody mediated allergic responses. Other less well understood mechanisms that have an immune component are also involved in respiratory hypersensitivity. OA is one outcome of respiratory hypersensitivity. Respiratory hypersensitivity and OA to proteins are primarily mediated by IgE antibody with subsequent inflammatory cell infiltrates. This same mechanism is responsible for OA to specific LMW chemicals such as the acid anhydrides and platinum salts. However, the role for IgE mediated responses in OA to other LMW chemicals such as the isocyanates and plicatic acid is poorly defined and other mechanisms may be responsible. 

There was an increased incidence of a mycoplasma respiratory tract infection in rats exposed to 260 ppm hexachloroethane for 6 weeks but not in rats exposed to lower doses or in other species. This could indicate compromised immune function or a weakened mucosal barrier along the respiratory epithelium. There were no studies identified that evaluated a wide range of immunological parameters. Therefore, there are no reliable LOAELs or NOAELs for this end point. Increases in spleen weights are not classified as LOAELs since they were not accompanied by histopathological changes. 

An increased incidence in mycoplasma infections in rats exposed to 260 ppm hexachloroethane for 6 weeks suggests that hexachloroethane might weaken resistance to infection (Weeks et al. 1979). This could be the result of either a change in the quantity or consistency of the respiratory tract mucus or a systemic weakening of the immune system. The data are inadequate to formulate any hypothesis regarding the mechanism for diminished host resistance or to postulate whether hexachloroethane in the environment might lower the resistance of humans to respiratory infections. 

Stumbles PA, Thomas JA, Pimm CL, Lee PT, Venaille TJ, Proksch S, Holt PG Resting respiratory tract dendritic cells preferentially stimulate T-helper cell type 2 (Th2) responses and require obligatory cytokine signals for induction of Thl immunity. J Exp Med 1998 188 2019-2031. 

In the context of allergies, sensitization is the process by which a person becomes, over time, increasingly allergic to a substance (sensitizer) through repeated exposure to that substance. Allergies are inappropriate or exaggerated reactions of the immune system to substances that, in the majority of people, cause no symptoms. Symptoms of the allergic diseases may be caused by exposure of the skin, the respiratory tract, or of the stomach and intestines to a protein or a chemical substance. 

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