Hipersensibilidades (Parte II - Hipersensibilidades dos tipos II, III e IV)

Summary

This educational video covers hypersensitivities, disorders caused by immune responses. It explains the four types of hypersensitivity, including Type 1 (allergic reactions), Type 2 (antibody-mediated disorders like autoimmune hemolytic anemia), Type 3 (immune complex-mediated conditions such as lupus), and Type 4 (T-cell mediated reactions seen in diseases like rheumatoid arthritis and multiple sclerosis). The video delves into the mechanisms, causes, and examples of diseases linked to each type, highlighting how immune responses can become pathological, leading to tissue damage and inflammation. The lesson provides an in-depth look at these immune system malfunctions and their clinical significance.

Takeaways

• 😀 Hypersensitivities are disorders caused by immune responses, and they occur when the immune reaction becomes excessive or harmful.
• 😀 Type 1 hypersensitivity (allergy) is mediated by IgE antibodies and involves mast cells, eosinophils, and Th2 cells.
• 😀 Type 2 hypersensitivity is mediated by antibodies and can result in diseases like autoimmune hemolytic anemia through opsonization and complement activation.
• 😀 The presence of autoantibodies in Type 2 hypersensitivity can lead to tissue damage by attacking surface antigens, receptors, and cells.
• 😀 Type 3 hypersensitivity occurs when immune complexes (antigen-antibody) are deposited in tissues, leading to inflammation and damage, such as in lupus or glomerulonephritis.
• 😀 The location of deposition of immune complexes (like blood vessels or kidneys) influences the clinical manifestations in Type 3 hypersensitivity.
• 😀 Type 4 hypersensitivity is mediated by T lymphocytes (CD4+ and CD8+) and involves inflammation caused by cytokine secretion or direct cytotoxic activity.
• 😀 Type 4 hypersensitivity is also known as delayed-type hypersensitivity (DTH) and is the cause of autoimmune diseases like rheumatoid arthritis, multiple sclerosis, and type 1 diabetes.
• 😀 In diseases like multiple sclerosis, T cells attack myelin in the central nervous system, leading to neurological deficits.
• 😀 Rheumatoid arthritis is characterized by inflammation in joints, where Th17 and Th1 cells recruit immune cells that destroy cartilage and bone.

Q & A

What are hypersensitivities?

Hypersensitivities are disorders caused by immune responses that are excessive or abnormal, leading to harmful or pathological reactions in the body.

How are hypersensitivities classified?

Hypersensitivities are classified into four types based on the type of immune response and the effector mechanism responsible for tissue injury. These types are Type 1, Type 2, Type 3, and Type 4 hypersensitivities.

What characterizes Type 1 hypersensitivity?

Type 1 hypersensitivity, also known as allergies or immediate hypersensitivity, is caused by IgE antibodies and involves mast cells, eosinophils, and their mediators. It is influenced by Th2 cells, which stimulate IgE production and inflammation.

How does Type 2 hypersensitivity lead to disease?

Type 2 hypersensitivity is mediated by antibodies that target antigens on cell surfaces. This can lead to opsonization, inflammation, and tissue damage, as seen in autoimmune diseases like autoimmune hemolytic anemia, where antibodies attack red blood cells.

What are the main mechanisms of tissue damage in Type 2 hypersensitivity?

In Type 2 hypersensitivity, antibodies can cause tissue damage through three main mechanisms: opsonization and cell destruction by phagocytes, inflammation induced by antibody deposition in tissues, and receptor activation or inhibition, such as in Graves' disease and myasthenia gravis.

What is the role of complement in Type 2 hypersensitivity?

In Type 2 hypersensitivity, the complement system is activated by opsonized cells, leading to further inflammation and cell destruction, as seen in autoimmune diseases like hemolytic anemia.

What causes Type 3 hypersensitivity?

Type 3 hypersensitivity is caused by the formation and deposition of immune complexes, which consist of antigens and antibodies (usually IgG). These complexes deposit in tissues like blood vessels, kidneys, and joints, leading to inflammation and tissue damage.

What are the common clinical manifestations of Type 3 hypersensitivity?

Common manifestations of Type 3 hypersensitivity include vasculitis, nephritis, and arthritis. A well-known example is systemic lupus erythematosus (SLE), where immune complexes deposit in various tissues.

How does Type 4 hypersensitivity differ from the others?

Type 4 hypersensitivity is a delayed-type hypersensitivity, mediated by T cells (CD4 and CD8). It involves the activation of T cells and the release of cytokines, leading to inflammation and tissue damage. Unlike the other types, it does not involve antibodies.

What are some examples of diseases caused by Type 4 hypersensitivity?

Type 4 hypersensitivity is implicated in diseases like rheumatoid arthritis, multiple sclerosis, type 1 diabetes, and psoriasis. In these conditions, T cells target and damage specific tissues.