Hypersensitivity and Autoimmunity

Flashcards covering key concepts related to hypersensitivity and autoimmunity, including definitions, types of reactions, mechanisms, and treatments.

What is hypersensitivity?

An abnormal or pathologic immune reaction caused by an immune response to repeated exposure to an antigen.

What are the four types of hypersensitivity reactions?

Type I, Type II, Type III, and Type IV hypersensitivity.

What is Type I hypersensitivity?

Also known as immediate or anaphylactic hypersensitivity, it is mediated by IgE and characterized by a rapid allergic response.

What role do mast cells and basophils play in Type I hypersensitivity?

Mast cells are the principal effectors, releasing mediators like histamine that enhance the allergic response.

What is a major clinical manifestation of Type I hypersensitivity?

Anaphylaxis, which is a severe systemic allergic reaction.

What is IgE?

An immunoglobulin primarily involved in Type I hypersensitivity and synthesized in the lymphoid tissues of the respiratory and gastrointestinal tracts.

What are the main effects of histamine released from mast cells during an allergic reaction?

Bronchoconstriction, increased vascular permeability, mucus secretion, and vasodilation.

How is Type II hypersensitivity characterized?

Also known as cytotoxic reactions, it involves IgG and IgM antibodies that react with antigens on cell surfaces.

What types of disorders are associated with Type II hypersensitivity?

Drug-induced hemolytic anemia, transfusion reactions, and autoimmune hemolytic anemia.

What is the difference between Type III and Type II hypersensitivity?

Type III involves soluble antigens forming immune complexes that can deposit in tissues, causing damage, while Type II involves antibodies reacting with surface antigens.

What is systemic lupus erythematosus (SLE)?

An autoimmune disease where the immune system attacks healthy tissues, leading to multiple organ involvement.

What is the role of T cells in Type IV hypersensitivity?

Sensitized T cells, particularly Th1 cells, mediate the response, which develops hours to days after exposure.

What is the primary mechanism of immunological tolerance?

It is the failure to mount an immune response to self-antigens, crucial for preventing autoimmune diseases.

What factors can trigger autoimmune diseases?

Genetic predisposition, environmental factors, gender, infections, and hormonal changes.

What is a common treatment strategy for autoimmune diseases?

Use of immunosuppressant drugs, anti-inflammatory medications, and symptom management approaches.

What are autoantibodies?

Antibodies that attack the body's own cells, tissues, or organs, leading to autoimmune disorders.

Define peripheral tolerance.

The lack of self-responsiveness of mature lymphocytes in the periphery to specific antigens.