Module 5: Immune System Flashcards
What are bacteria?
Prokaryotes (free living organisms)
What are viruses?
Non-cellular entities that are parasites of cells
Do viruses have a nucleus?
No
Do viruses have a genome?
Highly variable, in terms of DNA or RNA, single- or double-stranded
Do viruses have ribosomes?
No
Outer structure of viruses?
Envelope (membrane) or nucleocapsid
Replication strategy of viruses?
Rely on host cell for replication
What is a bacteriophage?
Viruses that infect bacteria (lytic or lysogenic)
What does lytic mean?
Capable of destroying/rupturing cell
What does lysogenic mean?
Nucleic material attaches to host’s DNA and remains dormant
What is the matrix/tegument of a virus?
Structure between the envelope and nucleocapsid of herpesvirus particles - stabilisation of viral envelope
What is a icosahedral capsid?
20 sides with 12 corners
What is a nucleocapsid virus?
Genome + capsid
What is a helical capsid?
Continuous helix of capsomers forming a cylindrical nucleocapsid
What is an enveloped virus?
Virus with additional membranous covering over the capsid in some animal viruses - do this by budding off host cell
What is difference between matrix and tegument?
Matrix = for stabilisation off of plasma membrane
Tegument = for stabilisation off of nuclear membrane
What are viral enzymes?
Enzymes contained within nucleocapsids, which aid in viral replication
What is negative RNA?
Single-stranded RNA not recognised by ribosomes; viruses carry this RNA into host cells to turn into positive RNA
What are rod (bacilli) bacteria?
Rod-shaped bacteria
What are spiral bacteria?
Curve-shaped bacteria
What are sphere (cocci) bacteria?
Spherically shaped bacteria
What is the periplasmic space?
Space between outer and inner membrane
What is a lipopolysaccharaide?
Large complex molecule comprised of polysaccharides linked to lipid molecules
Why are pilli/fimbrae important for bacteria?
Allow bacteria to attach to gut wall
How do bacterial flagella stay attached?
Have a flared foot that anchors inside cell
Structure of gram-positive bacterial cell wall?
Peptidoglycan (cell wall), periplasmic space, plasma membrane
Structure of gram-negative bacterial cell wall?
Thin peptidoglycan + outer membrane containing lipopolysaccharide, periplasmic space, plasma membrane
What is a gram stain?
Test to determine if bacteria is gram positive or gram negative
What is a cytopathic effect?
Structural changes in host cells caused by viral invasion
What is shedding?
Release of infectious virus from infected host by any means
What is a reservoir?
A place or organism where microorganisms survive, multiply, and await transfer to a susceptible host
What are virulence factors?
Properties of pathogen that allow it to successfully invade and cause disease in a host
5 transmission pathways?
- Respiratory
- Faecal-oral
- Zoonotic
- Blood-borne
- Sexually transmitted
What is cholera?
Disease that causes fatal diarrhoea and dehydration
What do cholera bacteria look like?
Kidney-shaped bodies with long flagella tail
Transmission type of cholera?
Faecal-oral
How is cholera treated?
Self-limiting disease; can be treated through oral rehydration therapy
What is influenza?
Highly contagious orthomyxovirus
Structure of influenza virus?
Single-stranded, enveloped, negative RNA virus (8 segments of genome)
Transmission type of influenza?
Respiratory (sneezing, coughing, droplets)
What are reservoirs of influenza?
Humans, pigs, birds
How is influenza treated?
Generally self-limiting by an immune response; or, oseltamivir (Tamiflu)
What does tamiflu do?
Inhibits neuraminidase, which is attachment of infected cells
What is antigenic shift?
Process by which two or more different virus strains, or strains of two or more different viruses, combine to form a new subtype having a mixture of the surface antigens of the two or more original strains
What is antigenic drift?
A mechanism for variation in viruses involving accumulation of mutations within the genes that code for antibody-binding sites
What is listeriosis?
Serious infection caused by food contaminated with Listeria monocytogenes
What do listeriosis bacteria look like?
Gram positive, motile, rod-shaped bacteria
What are reservoirs for listeriosis?
Humans, animals, soil, water; however, contamination actually comes from food
What is transmission type of listeriosis?
Eating contaminated foods (often soft cheeses and meats)
How does listeriosis act like a virus, despite being a bacteria?
Invades gut cells by having sipper-like interactions with surface proteins that causes endocytosis; then produces proteins that dissolve capsule and bacteria proliferates; excess bacterium have actin filaments that help then invade neighbouring cells
What is whooping cough caused by?
Bacteria called bordetella pertussis
Structure of bordetella pertussis?
Gram negative, non-motile, coccobacillus
Reservoirs of whooping cough?
Humans - particularly asymptomatic adults
Transmission of whooping cought?
Aerosols and direct contact
Catarrhal stage of whooping cough?
Lasts 2 weeks, may be mistaken as a cold; culture will be positive during this stage
Paroxysmal stage of whooping cough?
2 to 4 weeks, intense coughing and characteristic whooping cough upon inhalation; fatal in infants
Convalescent phase of whooping cough?
After 4 weeks; paroxysms decline and confers lasting immunity, though pneumonia, otitis media may occur after
How does whooping cough invade the cell?
Rides in the mucus and attaches to ciliated cells and proliferates; then releases toxins which destroy the cilia leading to a buildup of mucus
What are antibiotics?
Drugs that kill or prevent the growth of bacteria (not viruses) without killing healthy body cells
What is caused by a lack of surveillance from the immune system?
Cancer
What is caused by a lack of proper control of the immune system?
Autoimmune disease and allergies
What is caused by a weak/ineffective immune response?
Infectious disease
2 immune systems?
- Non-specific, innate
- Specific, adaptive
What is the innate immune system?
Rapid response that does not distinguish one invader from another
What is the adaptive immune system?
Does differentiate invaders; has a memory and adapts
What lines of defence are innate immunity?
- 1st external: skin, mucous membranes, secretions
- 2nd internal: phagocytic cells, antimicrobial proteins, inflammatory response, NK cells
What lines of defence are adaptive?
- 3rd: humoral (antibodies) and cell-mediated response
Where are leukocytes synthesised?
Bone marrow, through leukopoiesis
What is a common lymphoid progenitor?
Cells created by HSCs; gives rise to B cell and T cell precursors
What is a myeloid progenitor?
Gives rise to most non-specific, innate immune defence cells
3 types of granulocytes?
Neutrophils, eosinophils, basophils
What is haematopoiesis?
Blood cell formation
What immune cells are found in the blood? (5)
- NK cells
- T cells
- B cells
- Monocytes
- Basophils
What immune cells are found in the tissues?
Macrophages and mast cells
2 types of T cells?
Helper T cells and cytotoxic T cells
What are lymphocytes?
Type of WBC that attack foreign matter and act as source of viral defence
Role of neutrophils?
Drawn to site of infection; phagocytose bacteria
Role of eosinophils?
Lead body’s counterattack against parasitic worms, lessen severity of allergies by phagocytising immune complexes
Role of basophils?
Promote inflammatory response
What are monocytes?
Immature macrophages
2 anatomical barriers of immune system?
Skin and mucous membrane
Most superficial layer of skin?
Made of dead, keratinised cells, with little-to-no nutrition and a low pH; also replaces itself every 10-14 days
How does the mucous membrane act as a barrier?
Mucous traps bacteria; moved by ciliated cells to be removed
What are 3 physiological barriers of immune system?
Temperature, pH, chemical mediators
How does temperature act as a barrier?
Body’s natural temperature is not favourable for most pathogens
How does inflammation act as a barrier?
Inflammatory response is caused by leaking fluid of damaged cells/tissue, which causes an influx of phagocytic cells
What is the complement system?
Cascade of reactions; occur in response to stimuli which indicate foreign material
What is an alveolar macrophage?
Dust cell that does phagocytosis and has lots of lysosomes to cleave the ingested material; first line of defence against invading respiratory pathogens
2 main types of phagocytic cells?
- Neutrophils
- Macrophages
What are dendritic cells?
Spiny-looking cells with functions similar to macrophages, but instead of killing pathogen, they sample and report to T cells
What is a phagolysosome?
Structure resulting from fusion of phagosome and lysosome
Role of NK cells?
Convince infected cells to undergo apoptosis; kill intracellular pathogens
3 major events of an inflammatory response?
Vasodilation, increased capillary permeability, influx of phagocytic cells
What do histamines do?
Dilate blood cells
What is opsonisation?
Coating of a pathogen with antibodies to promote and enhance phagocytosis
First responder leukocytes of an inflammatory response?
Neutrophils
Secondary responder leukocytes of an inflammatory response?
Monocytes, which will then mature into macrophages
What is extravasiation?
Recruitment of neutrophils to exit blood near site of infection
What are cytokines?
Chemical messengers produced in response to a stimulus, which enhance inflammatory response
What is rolling?
Macrophages attaching and detaching from endothelial lining through blood cells
What is an antigen?
A toxin or other foreign substance that induces an adaptive immune response in the body, especially the production of antibodies
What are the epitopes/the antigenic determinants?
Certain regions of an antigen molecule that antibodies attach to to stimulate immune responses
2 types of adaptive immunity?
Humoral and cell-mediated
What is humoral immunity?
Humoral immunity is the aspect of immunity that results in antibody production (extracellular)
What is cell-mediated immunity?
Immune response that does not involve antibodies, but rather, involves the activation of cells like phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen (intracellular)
2 main types of lymphocytes?
B cell, T cell
Where do T cells mature?
Thymus
Where do B cells mature?
Bone marrow
What is a naive lymphocyte?
Mature B or T cell that has not yet encountered an antigen
What are the secondary lymphoid organs?
Spleen and lymph nodes
Role of lymph nodes?
Filter substances that travel through the lymphatic fluid, and contain lymphocytes
What is an effecter B cell?
Plasma cell
What are the effecter T cells?
Cytotoxic T cell (CD8+),
Helper T cell (CD4+)
What are antigen receptors?
Molecules capable of recognising specific antigens
What happens to a lymphocyte when the antigen binds to the receptors?
Division and differentiation
Why is it important that lymphocytes are circulated readily through the body?
Because they can only recognise one antigen type, so they should be exposed to as much area as possible
What is clonal selection?
Process which immature B and T cells undergo, in secondary lymphoid organs, so only certain types are permitted to mature to fight a specific antigen
What is clonal expansion?
Increase in the number of cells by mitotic cell division alongside clonal selection
What are memory B cells? Role?
Long-lived cells that do not secrete antibodies but will respond to antigens upon a second exposure
What is the role of immunoglobulin (Ig)?
Soluble B-cell receptor (BCR) secretion
How does an immunological memory develop?
- Naive lymphocyte will encounter an antigen for the first time
- Primary immune response kicks in 5-10 days and is short lived
- Weeks to years later, the response will be more rapid (3-5 days) and long lived (secondary immune response)
What is IgM?
First antibody formed by B cells during the immune response; confined to intravascular space due to large size
What is IgG?
Second antibody formed by B cells during the immune response; can move into extravascular space (the first responder in the case of a secondary immune response)
Where do antibodies come from?
Plasma cells (secretion)
Structure of an antibody?
Y shaped molecule, two heavy chains and two light chains, with two identical binding sites
How does the antigen bind to an antibody?
Non-covalent (reversible) binding, many factors involved such as hydrophilic/phobic
Why is an IgG response more effective than an IgM response?
Because IgG has a higher affinity
What is IgA?
Secretory antibody (mucosal antibody)
What is IgE?
Produced for parasitic infections and allergic reactions
Functions of antibodies?
Opsonisation, neutralisation, agglutination, complement system activation
What are cytokines?
Intercellular messengers; proteins that act on receptors to make the immune system work
What are the 3 modes of cytokine action?
Autocrine, paracrine (main), endocrine
What are MHC molecules?
Major histocompatibility complex molecules, also called HLA (human leukocyte antigens); hold little pieces of antigen so that the T cell can interact with the antigen
What is antigen processing?
The degradation of proteins into peptides that can bind MHC molecules for presentation to T cells
What T cell recognises MHC class I?
CD8
What T cell recognises MHC class II?
CD4
What is the costimulatory molecule?
A molecule along with cytokines and dendritic cells that activates i.e. reports to the T cell
How are B cells activated?
By cell-to-cell contact with Helper T-cells, and by direct contact with a pathogen (MCH II / CD4)
How are macrophages activated?
Interaction with T helper cells turns the macrophage into overdrive (MCH II / CD4)
What is the difference between a T cytotoxic cell and an NK cell?
Cytotoxic cells only recognise and kill MHC class I antigen class cells whereas NK cells are generalised
What is MHC class I?
- Produced in all nucleated cells
- Present endogenous (intracellular) antigens
What is MHC class II?
- Produced by all antigen-presenting cells (APCs) like dendritic cells or macrophages
- Present exogenous (extracellular) antigens
How do Helper T cells clear infection?
Produce cytokines
