Type III allergy

2 Mechanisms of Cell-Mediated Delayed Hypersensitivity Reactions (Th1) 

Which factors are critical in selecting and developing a T-lymphocyte-dependent response  

Why does a Th2-dependent response switch into aThl-dependent response, instead of regression or consolidation of symptoms  

T lymphocytes are called the conductors of the immunological orchestra. Twenty years ago Th and Ts lymphocytes were described, and then based on the released cytokines within the Th type, Thl was determined, which releases IFNy and a lym-photoxin, and Th2, which releases IL 4, IL 5, IL 10, and IL 13. Soon it became evident that there was a third subpopulation of lymphocytes—Thl7—involved in infectious immunity and autoimmunological processes. T lymphocytes need to be presented with an antigen in order to activate their functions. Therefore, it seems that the character and volume of stimulation are determined by the type and dose of an antigen, the mode of presentation in terms of costimulatory molecules, and finally the concentration and content of cytokines contained in stroma, as well as the stage in mechanism processes. 

Dendritic cells (DCs) are responsible for the recognition and presentation of antigens it was believed that there were two types of these cells, which underwent differentiation in the development from CD34 cells in bone marrow. They included dendritic lymphoidal and dendritic cells stemming from monocytes. The former ones were supposed to be responsible for activating Th2 lymphocytes and the latter ones, for stimulating Thl. This categorization was widely discussed. It was proved that, 

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In type III or immunocomplex-mediated allergy, IgG antibodies form complexes with antigen. At low exposures, the body is able to remove diese complexes, but if there is a severe exposure, immunocomplexes release a variety of proinflammatory cytokines. The involvement of this mechanism is clearest in serum sickness. This mechanism is also considered to be most important in the development of extrinsic allergic alveolitis (hypersensitivity pneumonitis, especially... 

C. Type III Drug Allergy Type III hypersensitivity is a complex type of drug allergy reaction that involves complement-fixing IgM or IgG antib ies and—possibly—IgE antibodies. Drug-induced serum sickness and vasculitis are examples of type III reactions Stevens-Johnson syndrome (associated with sulfonamide therapy) may also result from type III mechanisms. 

Chakir J, Shannon J, Molet S, Fukakusa M, Elias J, Laviolette M, Boulet LP, Hamid Q. Airway remodeling-associated mediators in moderate to severe asthma effect of steroids on TGF-beta, IL-11, IL-17, and type I and type III collagen expression. J Allergy Clin Immunol 2003 111 1293-1298. 

In Frullania, twenty-five taxa have been investigated chemically (27,34). Fourteen species contained allergy-inducing sesquiterpene lactones such as (322, 338, 339, 345, 349). Eighteen species bibenzyl derivatives (595—598, 600—608). The major constituents are sesquiterpene lactones and bibenzyls, which may be valuable chemosystematic markers of Frullania species. Frullania species are divided into five chemotypes, a sesquiterpene lactone-bibenzyl type (Type I), a sesquiterpene lactone-type (Type II), a bibenzyl-type (Type III), a monoterpene-type (Type IV) and a cyclocolorenone (38)-type (Type V). Except for the cyclocolenone-type, there is no chemical affinity between the Frullaniaceae and the Porellaceae. 

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