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in biology, the body’s acquisition of a specific increased sensitivity to heterologous substances, or allergens. Sensitization may be produced by bacterial and viral antigens and toxins, by chemical substances (including many medicinal agents), and by industrial poisons.
The sensitizing properties of various allergens not only depend on the quantity of the substance introduced but also on the substance’s qualitative features and the physical state of the antigens. Thus, a state of autosensitization most often develops against the body’s damaged proteins as a result of the formation of an allergen against one of the constituents of the tissues that have produced the allergen. Horse serum globulins and erythrocytes are more anaphylactogenic than albumins and hemoglobin. The repeated action of allergens on a sensitized body may cause such anaphylactic allergic reactions as Arthus reaction, which involves the development of an immediate local inflammatory edema, and serum sickness.
The period between the initial entry of an allergen into the body and the development of increased sensitivity to the allergen (this condition is called an allergy) is defined as the sensitization period. The sensitization period may last for a few days, several months, or even years. The initial stages in the development of allergic reactions resemble in many ways the development of immunity and are accompanied by the fixation of allergens in the cells of the reticuloendothelial system, the plasmatization of lymphoid cells, and the elaboration of antibodies in lymphoid cells. Cellular sensitivity increases in the body, and specific antibodies accumulate that are capable of uniting only with the allergen that caused their formation.
Sensitization is similar to immunity in that it may be active or passive. Both phenomena may develop simultaneously. The general principles of the origin and development of sensitization have been studied using active sensitization to allergenic serum as an example. Unlike immunization, sensitization is produced by minimal amounts of a sensitizing heterologous serum or some other heterologous protein and by chemical substances with low molecular weights, including medicines. Animals are sensitized in order to study certain disorders that correspond to human diseases associated with sensitization. Active sensitization is produced by an allergen dose that is significantly larger than the minimal dose; the dose varies for different animals, depending on the means and pathways of sensitization in the animal. Thus, guinea pigs are injected sub-cutaneously once or twice with 0.01 milliliters (ml) of horse serum or solutions of other protein allergens, rabbits are given 5–6 subcutaneous injections with 1–2 or 3–5 ml of horse serum, and dogs are given 0.2–0.5 ml/kg of horse serum once or twice. The subcutaneous method of sensitization is sometimes combined with intravenous treatment: the serum is injected subcutane-ously the first time and intravenously the second. Cats, African polecats, wolves, bears, and foxes may be sensitized in the same way. Monkeys are sensitized by repeated intravenous injections of small quantities of egg albumin.
Passive sensitization develops when a healthy animal is injected with the serum of an actively sensitized animal; 5–10 ml of the serum is used for guinea pigs and 15–20 ml for rabbits. Sensitization can be transmitted to another individual, for example, by transfusion, and can be eliminated or reduced by de-sensitization.
REFERENCESAdo, A. D. Obshchaia allergologiia. Moscow, 1970.
Immunological Diseases, 2nd ed., vols. 1–2. Boston, 1971.
V. A. ADO