6 topics with concise breakdowns: definitions, key facts, and class questions.
Immunopathological conditions are dangerous malfunctions of the immune system in which its protective potential turns against the body's own tissues. In this chapter, we analyze the mechanisms of hypersensitivity and the pathogenesis of autoimmune diseases at the cellular and molecular levels.
The section covers cytotoxic (type II), immune complex (type III), and cell-mediated (type IV) allergic reactions, as well as the fundamental principles of allergy treatment and prevention. A separate block is devoted to diseases of immune autoaggression: you will learn to clearly differentiate between their immune-dependent and immune-independent forms.
In seminars and exams, instructors most frequently require a detailed breakdown of the pathogenesis of tissue damage in type II and III reactions, as well as an explanation of the mechanisms triggering immune-independent autoaggression (e.g., in the disruption of blood-tissue barriers). Pay special attention to these topics—they form the clinical foundation essential for understanding internal medicine.
What is the main difference between type II allergy and a normal immune response?
Normally, cytotoxic reactions destroy foreign cells (bacteria, grafts). In type II allergy, antibodies attack the body's own cells, and the damage is massive and generalized in nature.
Which immunoglobulins are involved in type III reactions?
Precipitating antibodies of the IgG and IgM classes play the main role. Their key feature is the ability to form a precipitate upon contact with a soluble antigen.
Are antibodies involved in type IV reactions?
No, this is the key feature of delayed-type hypersensitivity. The reaction is entirely cell-mediated—by specific T-lymphocytes and macrophages.
Which drugs are foundational in the treatment of delayed-type allergies?
In delayed-type allergic reactions, corticosteroids and immunomodulators are used first and foremost. They allow effective control over the development of the immunopathological process.
What are "forbidden clones" in pathophysiology?
These are populations of mutated T- and B-lymphocytes, as well as antigen-presenting cells, that have lost the ability to distinguish "self" from "non-self". They mistakenly recognize normal body tissues as hostile antigens and begin attacking them.
Why are immune-independent diseases called antigen-dependent?
Because they develop independently of dysfunctions within the immune surveillance system itself. The primary cause is the emergence of a triggering antigen—a modified self-antigen, a "sequestered" barrier antigen, or a foreign antigen mimicking it.
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