Immunopathological Disorders of Pet Animals

Immunopathology is the study of disease conditions resulting from immune reaction. Immunopathological disorders mainly include the hypersensitivity, autoimmune and immunodeficiency disorders. In type-1 hypersensitivity, mast cell degranulation can lead to the release of inflammatory mediators including histamine, proteoglycans, serine proteases, and leukotrienes. Type-2 hypersensitivity is also known as cytotoxic hypersensitivity is rare reaction that is typically caused by IgG and IgM antibodies. In type-3 hypersensitivity, there is formation of antigen-antibody complexes, which gets deposited in various tissues and joints leading to various kinds of disease conditions. Type-4 hypersensitivity is called delayed type because it takes more than 24 hr to develop. There is allergic contact dermatitis, which mainly affects the pets and human beings. In pet animals, glomerulonephritis and systemic lupus erythematosus are the major autoimmune disease. Immunodeficiency disorders are seen in pet animals due to defects in congenital inertness of immune system. Common diseases like canine parvovirus and canine distemper causes immunodeficiency in dogs. Canine atopy is a type I hypersensitivity reaction to inhaled or cutaneously absorbed environmental antigens (allergens) in dogs caused by the moulds, weeds, and pollen grains. Flea allergy dermatitis is a type I hypersensitivity reaction, which is a common skin disease in dogs and cats sensitized to flea bites. Allergic contact dermatitis is type-4 hypersensitivity and most common disease of skin. Lethal acrodermatitis is primary immunodeficiency disorder, generally occurs in adult dogs due to T-cell defect and characterized by hypoplasia of T-cell dependent lymphoid tissues.