immune system functions Flashcards
immune system function
an important system that protects us from infection through various lines of defence
Pathogenic organisms
Organisms that cause disease by breaching tissues and causing damage or illness.
Commensal organisms
Organisms that live in a host without causing harm, often providing beneficial effects.
Viruses
Microscopic pathogens that consist of genetic material (DNA or RNA) surrounded by a protein coat. They require a host cell to replicate.
Bacteria
Single-celled microorganisms that can be pathogenic or beneficial. Some cause disease, while others play important roles in processes like digestion.
Parasites
Organisms that live on or inside a host, often causing harm. They include protozoa, helminths (worms), and ectoparasites like lice.
Microbiome
The community of microorganisms (bacteria, fungi, viruses) living in symbiotic relationship within our bodies, providing benefits like digestion and immune regulation.
Microorganisms that cause disease when they breach tissue barriers, leading to damage and illness. Examples include certain bacteria, viruses, fungi, and parasites.
Microorganisms that cause disease when they breach tissue barriers, leading to damage and illness. Examples include certain bacteria, viruses, fungi, and parasites.
Immune System Complexity
The immune system consists of different molecular and cellular processes that interact together to protect the body from pathogens.
Innate Immunity
Non-specific mechanisms that are innate to the host organism. Provides an immediate but generalized defense against infections and pathogens.
Adaptive Immunity
Specific mechanisms that adapt to particular pathogens. Also known as acquired immunity, it develops after exposure to a pathogen and offers long-term protection.
How does Innate Immunity work?
It responds to invaders using general mechanisms like phagocytes and inflammation without requiring previous exposure to the pathogen.
How does Adaptive Immunity work?
It targets specific pathogens after recognizing them through specialized receptors. This process creates memory cells for faster and stronger responses upon re-exposure.
Recognition in the Innate Immune System
Inherited defense mechanisms.
Phagocytes recognize common microbial motifs (PAMPs).
Provides non-specific, immediate defense against pathogens.
Recognition in the Adaptive Immune System
Uses random generation of receptors for pathogen recognition.
Generates a diverse set of immune cells, allowing the immune system to target specific parts of pathogens.
Provides specific, long-term immunity.
Innate vs Adaptive Immune System Recognition
Innate Immunity: Recognises broad, common features shared by many pathogens (e.g., PAMPs).
Adaptive Immunity: Recognises specific parts of pathogens through specialized receptors, enabling targeted responses.
Characteristics of Innate Immunity
Nonspecific and inherited.
Protects against foreign cells or substances without recognizing their specific identity.
Provides immediate defense without the need for prior exposure to invaders.
Does Innate Immunity require prior exposure?
No, innate immunity does not require prior exposure to pathogens. It recognises general, conserved properties that mark invaders as foreign.
How does Innate Immunity recognise invaders?
Innate immunity recognises general and conserved properties (such as PAMPs) that are shared by many pathogens, marking them as foreign.
Innate Immune Responses
Fast cellular responses (within minutes) involving phagocytosis and inflammatory processes.
Recognises invaders and recruits different immune cells to the site of infection.
Importance of Receptors in Innate Immunity
Receptors help in recognising invaders.
They recruit immune cells and produce proteins that aid in pathogen destruction.
Antimicrobial Proteins in Innate Immunity
Interferon: Inhibits viral replication inside host cells.
Complement: Helps kill microbes by forming pores in their membranes (MAC attack complex).
Components of Innate Immunity
Includes both humoral (antibodies, complement proteins) and cellular (phagocytes, neutrophils) responses.
Functions of the Innate Immune .
Phagocytosis – Engulfing and destroying pathogens.
Inflammatory processes – Recruit immune cells and initiate healing.
Antimicrobial protein activation – Production of interferons and complement to combat pathogens.
What is Phagocytosis?
Phagocytes (e.g., neutrophils, macrophages) engulf and destroy pathogens by digesting them inside the cell.
What is the role of Inflammatory Processes in Innate Immunity?
Inflammation recruits immune cells to the infection site, increases blood flow, and facilitates tissue repair.
What are Antimicrobial Proteins?
nterferons: Inhibit viral replication.
Complement proteins: Form pores in pathogen membranes, leading to their destruction.
What is Phagocytosis?
Phagocytosis is the process where phagocytes engulf and destroy particles (like pathogens) by endocytosis.
Main Types of Phagocytes
The main phagocytes include:
Neutrophils
Monocytes
Macrophages
Mast cells
Dendritic cells
These are also known as professional phagocytes.
How do Phagocytes reach the infection
Phagocytes move to the site of infection using chemotaxis, a process guided by chemical signals released by pathogens or damaged cells.
Professional Phagocytes
Professional phagocytes are specialised cells such as neutrophils, macrophages, and dendritic cells that excel at engulfing and destroying pathogens.
What are Resident Phagocytes?
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Resident phagocytes (sentinels) are found in most tissues and serve as the first line of defense against infections.
Role of Neutrophils in Phagocytosis
Neutrophils, a type of white blood cell, are the first responders to infection. They are recruited within minutes and play a key role in inflammation.
Role of Macrophages in Phagocytosis
Macrophages, found in tissues, arrive shortly after neutrophils. They are highly phagocytic and help clear pathogens and debris.
What is the Function of Mast Cells?
Mast cells, located in tissues, release histamine during allergic reactions and inflammation, contributing to immune responses.
Role of Dendritic Cells in Immunity
Dendritic cells act as a bridge between innate and adaptive immunity. They play an important role in the late stages of adaptive immune response by presenting antigens to T-cells.