Recognizing Invaders

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Immunology

Summary

The innate immune system is designed to fight against pathogens without any previous training. It achieves this by recognizing specific molecular structures that are common to microbes and damaged cells. Pathogen-associated molecular patterns (PAMPs) are typically found on pathogens such as bacteria and viral nucleic acids. Damage-associated molecular proteins (DAMPs) are common patterns found on the surface of injured or dead host cells. Pattern recognition receptors are receptors on cells of the immune system that can recognize PAMPs and DAMPs. Examples of pattern recognition receptors include: Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors, and RIG-I-like receptors. Once a receptor identifies a PAMP or DAMP, a signal pathway is triggered that activates transcription factors in order to express inflammatory and antiviral cytokine genes. These cytokines act as mediators of the immune system and facilitate the recruitment and activation of various cells to enact an immune response.

Lesson Outline

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FAQs

How do Helper T cells function within the immune system?

Helper T cells (TH cells), play a crucial role in the immune response. They do not interact directly with pathogens but operate as mediators within the immune system. After being activated by antigen-presenting cells (APCs), they release cytokines, substances that signal other immune cells to take action. The type of Helper T cell and the cytokines they produce determine the response provoked in other immune cells such as Killer T cells, Macrophages, and Eosinophils.

What is the function of type one Helper T cells (TH1) and how are they related to Interferon Gamma?

Type one Helper T cells (TH1) produce Interferon-gamma, a potent cytokine that is especially effective in combating certain viral and bacterial infections. Under the influence of Interferon Gamma and other cytokines like IL-12, TH1 cells predominantly activate macrophages, which are essential in the immune system's first line of defense. They also play a role in inflammatory reactions, contributing to different autoimmune diseases.

What roles do Type Two Helper T cells (TH2) play in the immune system, especially concerning allergic reactions?

Type Two T Helper cells (TH2) are responsible for the immune system's response to certain parasitic infestations. They produce specific cytokines, notably IL-4 and IL-5, which stimulate the action of mast cells, basophils, and eosinophils √ë cells that are central players in allergic reactions. Overactive TH2 response is often seen in allergy and asthma patients.

What is TH17 and why is it important in the context of autoimmune diseases and chronic inflammatory conditions?

TH17 cells represent a distinct lineage of Helper T cells that produce a specific set of cytokines, including IL-17 and IL-22. These influence the action of neutrophils and other inflammatory cells. Overactivity or dysfunction of TH17 cells has been implicated in several chronic inflammatory and autoimmune conditions, including psoriasis and rheumatoid arthritis.

How does the balance between different types of Helper T cells affect the immune response?

The balance between TH1, TH2, and TH17 cell types is critical for a properly functioning immune system. Certain diseases can result from an imbalance in this system. For instance, an overactive TH1 response may contribute to autoimmune diseases while an overactive TH2 response may lead to allergic reactions. A nuanced understanding of these systems can help in the development of targeted therapies for immune-related conditions.

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