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?
.
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.
Steps of Phagocytosis
Recognition: Phagocytes recognise and bind to the pathogen.
Pseudopod Formation: The phagocyte extends its membrane to form pseudopods around the pathogen.
Ingestion: The pathogen is engulfed, forming a phagosome.
Phagosome and Lysosome Fusion
After ingestion, the phagosome fuses with a lysosome to form a phagolysosome, where the pathogen is exposed to digestive enzymes.
Digestion in Phagocytosis
Within the phagolysosome, enzymes and reactive oxygen species digest and destroy the engulfed pathogen.
What happens to the Waste in Phagocytosis
Indigestible materials and waste products are expelled from the phagocyte by exocytosis after digestion.
Antigen Presentation in Phagocytosis
After digestion, phagocytes present antigens from the pathogen on their surface to activate T-cells, linking innate and adaptive immunity.
What are Leukocytes?
Leukocytes, or white blood cells, are crucial components of the immune system involved in defending the body against infections and foreign substances.
Role of Neutrophils
Phagocytise and kill bacteria
Mediate inflammation
First responders to sites of infection
Function of Eosinophils
Release chemicals to kill parasites
Phagocytize certain parasites
Participate in allergic responses
What are Monocytes?
Develop into macrophages when they migrate into tissues
Play a role in phagocytosis and immune response
Role of Macrophages
Phagocytize microbes
Mediate inflammation
Present antigens to T cells to activate adaptive immunity
Function of Basophils
Enter tissues at the site of injury
Secrete anticoagulant factor, heparin
Involved in inflammatory responses
What are Natural Killer Cells?
Attack cancerous and virus-infected cells
Play a role in both innate and adaptive immunity
Role of Dendritic Cells
Similar to macrophages
Act as a bridge between innate and adaptive immunity by presenting antigens
Function of Mast Cells
Secrete histamine during inflammatory responses
Participate in allergic responses
What triggers Inflammation?
Infection and injured cells release chemicals that stimulate inflammation.
Purpose of Inflammation
The primary purposes of inflammation are to:
Prevent the spread of infection.
Heal damaged tissue following pathogen clearance.
Key Cells Involved in Inflammation
Key cells in inflammation include:
Phagocytes: Neutrophils, macrophages, dendritic cells, and mast cells.
How are Phagocytes Activated?
At the onset of infection, phagocytes are activated by Pattern Recognition Receptors (PRRs) that recognize a wide range of molecules shared by pathogens.
What are Pathogen-Associated Molecular Patterns (PAMPs)?
PAMPs are broad molecular patterns recognized by PRRs, indicating the presence of pathogens and triggering the innate immune response.
Characteristics of Inflammation
Inflammation is characterised by:
Redness (rubor)
Heat (calor)
Swelling (tumor)
Pain (dolor)
What happens upon recognition of PAMPs?
Upon recognition of PAMPs, inflammatory mediators such as cytokines and chemokines are released by immune cells.
Role of Cytokines in Inflammation
Cytokines mediate the inflammatory response and can induce fever to help fight infection.
What are Chemical Factors in Inflammation?
Chemical factors involved in inflammation include:
Histamine
Bradykinin
Serotonin
Leukotrienes
Prostaglandins
How do Chemical Factors Affect Blood Vessels?
These chemical factors cause vasodilation of blood vessels, increasing blood flow and permeability to attract neutrophils and beneficial proteins to the injury site.
What is the Role of Neutrophils in Inflammation?
Neutrophils are attracted to the site of infection to clear pathogens and subsequently summon additional leukocytes, including lymphocytes important for adaptive immunity.
What is the overall purpose of inflammatory mediators?
nflammatory mediators help coordinate the immune response by facilitating communication between cells, promoting blood flow, and ensuring that immune cells are recruited to sites of infection or injury.
What happens when an injury introduces bacteria beneath the skin?
Bacteria entering beneath the skin trigger mast cells to secrete histamine, while endothelial cells secrete nitric oxide.
What effect does histamine have during inflammation?
Histamine causes capillaries to dilate and become leaky, allowing fluid and immune cells to exit the capillaries and enter the site of the wound.
What is the role of neutrophils in the inflammatory response?
Neutrophils exit the capillaries to reach the wound site, where they engulf and destroy bacteria, helping to control the infection.
What happens to capillaries after the infection is controlled?
After neutrophils and macrophages have cleared the infection, the capillaries return to normal function as the inflammatory response subsides.
What is the overall process of the inflammatory response after an injury?
. Injury introduces bacteria.
2. Mast cells secrete histamine; endothelial cells secrete nitric oxide.
3. Capillaries dilate and become leaky.
4. Fluid and neutrophils exit capillaries into the wound.
5. Neutrophils and macrophages clear the infection.
6. Capillaries normalize after infection contr
What is Interferon?
Interferon is a cytokine that inhibits viral replication inside host cells and is not specific to any particular virus.
What role does Interferon play in the immune response?
interferon helps protect neighboring cells from viral infection by inhibiting their replication, thus limiting the spread of the virus
What is the Complement System?
The complement system is a group of proteins that can kill microbes without the need for phagocytosis
How does the Complement System kill microbes?
It uses the membrane attack complex (MAC) to create channels in the microbial plasma membrane, leading to the lysis and bursting of microbes
What are the key functions of Antimicrobial Proteins?
Antimicrobial proteins like interferon and complement:
Inhibit viral replication (Interferon).
Directly kill microbes (Complement).
Enhance the effectiveness of the immune response.
What happens to pathogens that evade the immune system?
Pathogens, such as viruses, can manage to infect host cells despite the immune response.
What do infected host cells produce in response to infection?
Infected host cells produce “distress” ligands that signal to the immune system that they are compromised.
How do Natural Killer (NK) cells respond to infected host cells?
NK cells recognize the distress ligands produced by infected cells and can then target and destroy these compromised cells
What is an additional role of Natural Killer (NK) cells?
NK cells are also important in cancer surveillance, identifying and eliminating cancerous cells that display abnormal characteristics.
What is the significance of NK cells in the immune response?
NK cells provide a critical line of defense against viral infections and tumors by recognizing and killing infected or malignant cells.
What is the definition of Adaptive Immunity?
Adaptive immunity creates immunological memory for long-term protection and provides specific immunity to each pathogen encountered.
How long does it take for the adaptive immune system to become established?
The adaptive immune system takes days or even weeks to become fully established after encountering a pathogen.
What is a key feature of the adaptive immune response?
A key feature of the adaptive immune response is its ability to develop specificity for each pathogen it encounters.
Why is immunological memory important in the adaptive immune system?
Immunological memory allows the immune system to respond more rapidly and effectively upon subsequent exposures to the same pathogen.
What are the two main types of responses in the adaptive immune system
The two main types of responses in the adaptive immune system are humoral immunity (involving antibodies) and cell-mediated immunity (involving T cells).
What are the two main types of immune systems?
The two main types of immune systems are the Innate Immune System and the Adaptive Immune System.
How does the Innate Immune System respond to pathogens?
The Innate Immune System provides a non-specific and immediate response to pathogens, using barriers and phagocytic cells.
How does the Adaptive Immune System respond to pathogens?
The Adaptive Immune System offers a specific response to pathogens, taking days to weeks to develop, and creates immunological memory.
What is the nature of recognition in the Innate Immune System?
The Innate Immune System recognizes pathogens through inherited mechanisms and general patterns (e.g., PAMPs).
What is the nature of recognition in the Adaptive Immune System?
The Adaptive Immune System involves random generation of recognition, allowing for diversity in responses to specific pathogens.
What types of cells are primarily involved in the Innate Immune System?
The Innate Immune System primarily involves phagocytes (e.g., neutrophils, macrophages) and natural killer (NK) cells
What types of cells are primarily involved in the Adaptive Immune System?
The Adaptive Immune System primarily involves B cells (producing antibodies) and T cells (cell-mediated response).
What is a key advantage of the Adaptive Immune System?
A key advantage of the Adaptive Immune System is its ability to develop immunological memory, providing long-term protection against previously encountered pathogens.
What is a key feature of the Innate Immune System?
A key feature of the Innate Immune System is its immediate response to pathogens without prior exposure.
