Type IV Hypersensitivity |T- Cell mediated Hypersensitivity |Mechanism | Examples

ilovepathology
9 Apr 202412:46

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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الوسوم ذات الصلة
Immune SystemHypersensitivityType IVInflammationCytokinesT-CellsPathologyEducationalHealthcareMedical LearningInflammatory Diseases
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