15 concise topics with breakdowns: definitions, key facts, and class questions.
This section covers the morphological manifestations of immune system disorders. We will analyze the basics: how the mechanisms of innate, adaptive, and cellular immunity work, as well as the role of natural killer cells and the causes of breakdown in immunological tolerance.
The primary focus is placed on clinical morphology. You will study the tissue manifestations of hypersensitivity reactions (types I, II, and III), mechanisms of transplant rejection, and the nature of autoimmune diseases. Special attention is given to primary immunodeficiencies and HIV infection, the pathogenesis of which systematically destroys the body's protective barriers.
During practical classes and exams, the morphology of hypersensitivity reactions and gross and microscopic specimens in HIV infection are tested most stringently. Additionally, amyloidosis (systemic and localized) becomes a classic "stumbling block" for students—make sure to understand its pathogenesis, specific histological stains (Congo red), and types of amyloid.
What happens if innate immunity fails to cope with an infection?
If the first line of defense (macrophages and granulocytes) is breached, the body triggers a specific (adaptive) immune response aimed at destroying the specific pathogen.
What is immunological tolerance?
This is a state of stable specific unresponsiveness of the immune system to the body's own tissues. When this mechanism is impaired, an autoimmune response develops.
How do cytotoxic T lymphocytes kill infected cells?
They destroy target cells through direct cell-to-cell contact. CTLs (CD8+) recognize endogenous peptides in the complex with MHC class I and induce antigen-specific cell lysis.
Which lymphocyte population do natural killer cells belong to?
Natural killer (NK) cells are classified as an independent, third lymphocyte population that functions alongside the more well-known first and second populations—T and B cells.
What happens if the body loses the ability to distinguish "self" from "non-self"?
Impairment of this crucial recognition ability underlies the development of autoimmune diseases, in which immunity begins to destroy its own tissues.
Can mast cell degranulation occur without the involvement of an allergen?
Yes, activation can be caused by complement anaphylatoxins (C3a, C5a), interleukin-8, physical factors (cold, heat, solar radiation), and certain drugs, such as morphine or codeine.
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