Contact sensitization

April 12, 2018 22:30 | Symptoms And Treatment
This is a special form of cell-type reactions. The clinical equivalent is allergic contact eczema( or contact dermatitis).This is the most common, mainly( up to 1/3 of cases) professional, skin disease.

Pathogenesis of .The main studies were carried out on experimental models, in particular, by sensitization of guinea pigs DNCP, picryl chloride, oxazolone, potassium bichromate. The immune response of the organism is obviously controlled by genetic factors, as evidenced by the association of the disease with certain antigens of the HLA system( A3 and B7).According to Polak, the development of the pathological process involves certain stages.

1. Sensitization phase( primary reaction):
a) preparative stage,
b) recognition stage,
c) proliferation and differentiation,
d) propagation stage.

2. Effector phase( secondary reaction).

The phase of sensitization. In the preparative stage, the hapten, penetrated into the dermis through the stratum corneum and the intercellular spaces of the epidermis, is phagocytosed by macrophages. Already in the epidermis, its covalent binding with carrier proteins occurs. From the dermis, the hapten enters the lymph and peripheral blood. The antigen is recognized by T-lymphocytes with the help of appropriate receptors. According to Thomas, antigenic stimulation can be mediated: macrophages are the first to perceive and process the hapten, so they are called stimulant cells. Along with macrophages, Langerhans cells can play this role. In the next stage, specifically stimulated lymphocytes and / or Langerhans cells migrate to the regional lymph nodes where proliferation and differentiation occur in the paracortical thymus-dependent zones. Cell division leads to the formation of immunoblasts with large nuclei and pyroninophilic cytoplasm, which in turn turn into small lymphocytes with the function of memory cells or effectors. From the lymph nodes cells that are sensitized to a specific hapten enter the circulation and are carried throughout the body. In general, the phase of sensitization lasts 5-7 days. Along with memory cells and effectors, the 3rd subpopulation, suppressor cells, was identified.

Effector phase of .If the number of specific effector cells is small, they are not capable of provoking a response like the secondary response. The mechanism of the reaction is enhanced by the production of soluble mediators, primarily lymphokines. They involve other types of peripheral blood cells in an allergic reaction. Obviously, lymphokines are not the only mediators involved in contact sensitization, mediators of mast cells play a role.