Module 2 Flashcards
Branches of the immune system
What are the 2 branches of the immune system?
Innate and Adaptive
What are the 4 components of Innate Immunity?
- Immune Barriers
- Inflammation
- Pattern-Recognition
- Phagocytosis
What are the 3 types of immune barriers of the innate immune system?
- Physical
- Cellular
- Soluble
What are the physical barriers of the innate immune system?
Every structure located at the interface between the inside and the outside of the body
Eg: Skin, cilia, and bodily secretions
Prison Break Analogy: Physical Barrier of innate immune system
Prison walls and the prison cell which are the first obstacles that a prisoner needs to break through in order to escape
What are the cellular barriers of the innate immune system?
Made of the various cells which play a role in the innate immune response (covered in module 01) eg: Neutrophils, macrophages, dendritic cells and NKCs
Prison Break Analogy: cellular Barrier of innate immune system
Prison guards, their role is to monitor the prison and make sure that everything is in order
What are the soluble barriers of the innate immune system?
Made of macromolecules which contribute to the mediation of an innate immune response
eg: Complement and cytokines
Prison Break Analogy: Soluble Barrier of innate immune system
Communication system inside the prison which includes radios and cameras
What are the 2 categories components of the physical barrier of the innate immune system?
- Physical
- Chemical
What are the physical components of the physical barrier of the innate immune system?
(1) Skin
(2) Mucous membranes; cover cavities of the body (respiratory, GI, Urinary, reproductive) they contain specialized structures such as cilia and produce mucous
What are cilia?
Hairlike vibrating structures that can trap particles, preventing them from reaching vulnerable areas of the mucous membranes
What is mucous?
Viscous substance secreted by mucous membranes
How do cilia and mucous add protection from pathogens?
Microorganisms get caught in sticky mucus which prevent them from reaching the lungs. Then the cilia of the respiratory tract sweep these organisms up and out of the body through coughing or sneezing
What are the chemical components of the physical barrier of the innate immune system?
Mucous membranes secrete chemical component to attach and kill bacteria
- tears and Saliva contain lysozyme
- Gastric acid destroy most bacteria and toxins that enter the stomach
What are the four major cell types of the cellular barrier of the innate immune system?
(1) Neutrophils
(2) Macrophages
(3) Dendritic Cells
(4) Natural Killer Cells
Describe Neutrophils and its role in the innate immune system (5 characteristics)
(1) Most common leukocyte found in blood of mammals
(2) Phagocytes that patrol the body to find, engulf, and destroy pathogens
(3) Circulate in the blood (12hrs) before entering tissues by diapedesis
(4) Recruited to a site of infection by resident macrophages that have encountered pathogens
(5) Lifespan of 1 to 3 days after entering the tissues
What is diapedesis?
Process by which blood cells, such as neutrophils, move from blood to tissues by passing through intact vessel walls. This process, also called extravasation.
Describe Macrophages and its role in the innate immune system (4 characteristics)
(1) Phagocytes that patrol the body to find, engulf, and destroy pathogens
(2) can either take up residence in a specific tissue, or move freely/patrol throughout a larger area of tissues
(3) Contribute to tissue repair and present antigens to other immune cells such as T-cells
(4) Become activated after phagocytosing pathogens or in response to cytokine signalling
Describe Dendritic Cells and its role in the innate immune system (4 characteristics)
(1) Phagocytes that are often in contact with the external environment (specifically Langerhans DC)
(2) Engulf foreign antigens that have evaded the initial barriers of the innate immune system
(3) Present antigens on their cell surface through peptide: MHC complexes, which can be recognized by helper T-cells
(4) Major link between the innate and adaptive immune systems
Describe Natural Killer Cells and its role in the innate immune system (3 characteristics)
(1) Recognize abnormal cells lacking antigen specific receptors
(2) Destroy abnormal cells of the body, which include tumorous and virus-infected cells
(3) Bind to cell surface of target cells and release chemical causing pores to form in the cell membrane, leading to their lysis
What are the 2 major categories of macromolecules that make up the soluble barriers?
Complement System
Cytokine
What is the Complement System?
Made up of over 30 soluble proteins
Where is the Complement System?
Circulate in the blood, normally in an inactive form
When is the Complement System activated?
Directly activated in the presence of extracellular pathogens
Indirectly activated by pathogen-bound antibody
What happens when the Complement System activated? (2)
Leads to the formation of the “Membrane Attack Complex” (MAC)
Enhances, or complements, the efficiency of other immune functions, such as inflammation and phagocytosis
What is the Membrane Attack Complex?
Structure made of activated complement proteins which have the ability to destroy extracellular pathogens by creating holes in their cell membrane, which leads to lysis and cell death. As a side effect of this process, MAC can also damage host cells
What are the 3 major pathways that can activate the complement system?
Classical
Alternative
Lectin
What are the 3 major functions of the Complement System?
Inflammation
Phagocytosis
Membrane Attack Complex
Describe the inflammation process of the Complement System
- Attraction of various immune cells to the site of infections through the release of chemotactic molecules
- Activated complement proteins bind to complement receptors on immune cells (eg Mast cells and basophils) inducing the release of chemotactic molecules
What are chemotactic molecules?
Inducing the movement of cells toward the site where the substances are originally released
Ex: Histamines and Cytokines
Describe the role of the Complement System in phagocytosis
Activated complement proteins, predominanttely C3b, opsonize pathogens thereby targeting them for destruction by phagocytes
What is “opsonize”?
Making a foreign particle more susceptible to phagocytosis by binding to the antigen and marking it for ingestion
What would be the result of a complement deficiency?
Reduced lysis of microbes and less inflammation. Would result in reduced bacterial clearance and therefore longer periods of infection
What are cytokines?
Small proteins secrete by various immune cells in response to a number of different stimuli.
They are chemical mediators that play a key role in cell-to-cell communication
Large variety exists and each have a strong affinity for a specific type of cytokine receptor
What is the major role of cytokine signalling ?
regulate immune processes, such as immune responses, inflammation, and hematopoiesis
Compare and Contrast; Autocrine, Paracrine, Endocrine
Autocrine: Sending and receiving cells is the same
Paracrine: Sending and receiving cells are near each other (neighbouring)
Endocrine: Sending and receiving cells are distant from each other
Does the majority of cytokines have an autocrine, paracrine or endocrine effect?
Majority act locally, so autocrine and paracrine
Give 4 essential characteristics of cytokines
(1) Have paracrine and auticrine effects
(2) They have high specificity and affinity to their receptor
(3) They alter gene expression
(4) They can be pro-inflammatory or anti-inflammatory
Prison Break analogy: cytokines
Prison communications systems, appropriate orders need to be senf to a specific person or to a specific location. If you want the information to be correctly communicated, you need to use the correct radio channel and you need to specific to whom you are talking to
What are the 2 main groups of cytokines?
Pro-inflammatory
Anti-inflammatory
Describe pro-inflammatory cytokines
Made by most immune cells. When secreted these cytokines will induce an inflammatory response within the body
Describe anti-inflammatory cytokines
Made by several immune cells and work to limit the inflammatory response within the body. They inhibit pro-inflammatory cytokines production and activating immune cells that promote healing
What happens if you have a deficiency in anti-inflammatory cytokines?
Pro-inflammatory surplus will lead to complications such as tissue damage due to an excessive inflammatory state
What happens if you have a deficiency in pro-inflammatory cytokines?
Anti-inflammatory surplus will result in a lack of an immune response to a pathogen which can result in spreading of the pathogen
What is inflammation?
Series of biological reactions in response to the invasion of harmful infections agent into the body.
Occurs as a localized tissue response to injury or invasion
Has both local and systemic effect within the body
How can inflammation be characterized?
By any of these 5 physical responses:
- Redness
- Heat
- Pain
- Swelling
- loss of function
What are components of the inflammation process?
- Alteration of blood flow to the injured area
- Influx of phagocytic and other immune cells
- Removal of foreign antigens
- Healing of damaged tissue
What is the main purpose of inflammation?
Body’s attempt at self protection by removing harmful stimuli, including damaged cells, irritants, or pathogens
It localizes and eliminates the invading pathogen, in an effort to stop it from spreading, and to remove damaged tissue
What are the major events of Inflammation? (5)
(1) Breach of the physical barrier
(2) Vasodilation: Increase in blood vessels diameter. Induced by vasoactive and chemotactic factors
(3) Permeabilization of the capillaries facilitates entrance of fluids in tissues. Induced by vasoactive and chemotactic factors +Vasoconstriction of vessels carrying blood away from area
(4) Extravasation: Cells move from the blood to the tissues/site of infection by chemotaxis
(5) Phagocytosis: Phagocytic immune cells (eg: neutrophils and macrophages) engulf the pathogens
What are the first cell to arrived to the site of infection?
Neutrophils