Type IV Hypersensitivity |T- Cell mediated Hypersensitivity |Mechanism | Examples
Summary
TLDRThis tutorial delves into type four hypersensitivity reactions, focusing on cell-mediated immunity. It explains how CD4+ T cells produce cytokines leading to chronic inflammation. The video outlines the pathogenesis of delayed-type hypersensitivity, highlighting T helper 1 and T helper 17 responses. It also covers clinical examples like tuberculin reactions and contact dermatitis, and discusses T cell-mediated cytotoxicity in diseases like type 1 diabetes and rheumatoid arthritis. The tutorial encourages active learning through practice tests on Visia, an engaging platform for medical knowledge.
Takeaways
- 🧬 Type Four Hypersensitivity, also known as cell-mediated hypersensitivity, is primarily caused by inflammation resulting from cytotoxic T cells.
- 🔬 CD4 positive T cells produce cytokines that lead to chronic inflammation, often in response to environmental or self-antigens.
- 🌟 Delayed Type Hypersensitivity (DTH) is a prototype of T-cell mediated inflammation, detectable within 24 to 48 hours post-antigen exposure.
- 🔍 T helper 1 (Th1) and T helper 17 (Th17) cells are key contributors to DTH, with Th1 promoting macrophage activation and Th17 recruiting neutrophils.
- 🛡 The pathogenesis of DTH involves the activation of CD4 positive T cells, differentiation into effector T cells, and resulting inflammation and tissue injury.
- 🔄 Upon re-exposure to an antigen, memory T cells, which are long-lived, respond quickly to prevent further inflammation.
- 💉 Clinical examples of CD4 positive T cell-mediated inflammation include tuberculin reactions and contact dermatitis.
- 🛑 In persistent antigen scenarios, such as with Mycobacterium tuberculosis, T helper one cells can lead to granuloma formation, a hallmark of granulomatous inflammation.
- 🚨 CD8 positive cytotoxic T lymphocytes kill antigen-expressing target cells through apoptosis, a key mechanism in cell-mediated immunity.
- 🏥 Diseases mediated by T cell cytotoxicity include type 1 diabetes, graft rejection, and responses against viruses and tumor cells.
- 📚 The script concludes with a summary of type four hypersensitivity, its mechanisms, and examples, encouraging active learning through practice tests and feedback on the Visia platform.
Q & A
What is type four hypersensitivity?
-Type four hypersensitivity, also known as cell-mediated hypersensitivity, is primarily caused by inflammation resulting from cytotoxic T cells, which are produced by CD4 positive T cells.
What are the main cells involved in type four hypersensitivity reactions?
-The main cells involved in type four hypersensitivity reactions are CD4 positive T cells, which produce cytokines leading to inflammation.
What type of inflammation is typically associated with type four hypersensitivity?
-Type four hypersensitivity is most often associated with chronic inflammation.
Which T helper cells contribute to delayed type hypersensitivity?
-T helper 1 (Th1) and T helper 17 (Th17) cells contribute to delayed type hypersensitivity.
What is the role of interferon gamma in T helper 1 cells?
-Interferon gamma, produced by T helper 1 cells, promotes further helper cell development and activates other immune cells, such as macrophages.
How do T helper 17 cells respond to extracellular pathogens?
-T helper 17 cells produce interleukin-17 and other cytokines and chemokines, which recruit more neutrophils and monocytes to promote inflammation against extracellular pathogens.
What happens to effector T cells after the inflammation is cleared?
-After the inflammation is cleared, effector T cells transform into memory T cells, which are long-lived and respond quickly to the same antigen if encountered again.
What are the clinical examples of CD4 positive T cell-mediated inflammatory reactions?
-Clinical examples of CD4 positive T cell-mediated inflammatory reactions include tuberculin reaction and contact dermatitis.
What is the difference between T helper 1 and T helper 17 in terms of the pathogens they target?
-T helper 1 cells target intracellular pathogens, such as some bacteria and viruses, while T helper 17 cells handle extracellular bacteria and fungi.
How do activated CD8 positive cytotoxic T lymphocytes kill target cells?
-Activated CD8 positive cytotoxic T lymphocytes kill target cells by inducing apoptosis, either through the Fas ligand and Fas receptor interaction or by forming a perforin and granzyme complex.
What are some diseases associated with T cell-mediated cytotoxicity?
-Diseases associated with T cell-mediated cytotoxicity include type 1 diabetes, graft rejection, reactions against various viruses, and destruction of some tumor cells.
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