Immunology Flashcards
What is immunolgy?
The study of an organism’s defense system
What is the immune system composed of?
Organs (spleen)
Cells (T-cells)
Molecules (antibodies)
What are 4 microbes?
Viruses
bacteria
Fungi
Protozoa
What are the 5 organs of the immune system?
Tonsils
Thymus
Spleen
Bone marrow
Lymph nodes
What is a primary lymphoid organ?
Production of white blood cells
What is a secondary lymphoid organ?
Sites where immune responses are initiated
Describe the spleen in terms of the secondary lymphoid organs
Site of initiation for immune responses against blood-borne diseases
Describe bone marrow in terms of the primary lymphoid organs
Source of stem cells that develop into innate and adaptive immune responses
Describe the thymus in terms of primary lymphoid organs
School for T cells to learn not to react to the wrong cells
Describe the lymph nodes in terms of secondary lymphoid organs
Located along lymphatic vessels
Drains lymph fluid and filters from blood and tissues
Site of initiation of immune Reponses
What is the epidermis comprised of?
Dead cells, keratin, and phagocytic immune cells
What is the dermis comprised of?
Thick layer of connective tissue, collagen, blood vessels
What layer of the skin are the dendritic cells located?
Dermis
What is the purpose of a lysozyme?
Breaks down bacterial cells walls on the skin
Describe the skin’s chemical defense system
Pores which secrete:
- Lysozymes
- Sebum (low pH)
- Salt (hypertonic)
Where are the mucosal membranes?
Ocular (eye)
Respiratory (throat/lungs)
Oral (stomach)
Urogenital/rectal
What is a mucosal membrane?
Live layer of mucus producing cells
Describe the process of the mucociliary escalator
Dust and other particles get stuck on the mucus. Cilia move the mucus up the pharynx.
What are the chemical defenses of the mucosal surfaces?
Stomach
Gall Bladder
Intestine
Mucus
Defensins
Lysozymes
What is the function of the stomach as a chemical defense of mucosal surfaces?
Low pH
What is the function of the gall bladder as a chemical defense of mucosal surfaces?
Bile
What is the function of the intestine as a chemical defense of mucosal surfaces?
Digestive enzymes
What is the function of the lysozymes as a chemical defense of mucosal surfaces?
Tears, urine
Which has more layers, skin or the mucous membranes?
Skin
Are the cells of the mucous membranes loosely packed?
No
Is sebum present in mucous membranes?
No
Is cilia present in skin?
No
What are the two surface barriers of the immune system?
Skin and mucous membranes
What is the difference between innate and adaptive immunity?
Innate immunity is rapid, and because it is already in place, has limited specificities and no specific memory.
Adaptive immunity is variable, and is highly specific, it can ‘learn’ and therefore has a long-term memory
What parts of the immune system are part of the innate immunity?
Surface barriers
Internal defences
What are the internal defences?
Phagocytes
Natural Killer Cells
Inflammation
Antimicrobial properties
Fever
What parts of the immune system are part of the adaptive immunity?
Humoral Immunity
Cellular Immunity
What are the humoral immunities?
B cells
What are the cellular immunities?
T cells
What is blood composed of?
Plasma and Cells
What is plasma composed of?
Proteins
Other solutes
Water
What are the formed elements of blood?
Platelets
White blood cells
Red blood cells
What are the two types of blood cells derived from hematopoietic stem cells?
Myeloid
Lymphoid
Red blood cells are what kind of cell?
Myeloid
B and T cells are examples of what kind of cell?
Lymphoid
White blood cells
Granulocytes, monocytes, dendritic cells, and platelets are all types of what cell?
Myeloid
White blood cells (except platelets)
What is the purpose of a granulocyte in the blood?
Circulate in the blood and can move into tissue during inflammation
What is the function of a neutrophil
Highly phagocytic, numbers increase with infection
What is the purpose of granulocytes in tissue?
Mast cells
Line mucosal surfaces
Releases granules that attract white blood cells to areas of tissue damage
Are fast acting
What is the purpose of monocytes?
When they are present in the blood, they have low phagocytosis
When they enter tissues, they become highly phagotic macrophages
What is the purpose of a macrophage?
They are either sessile or migratory
- Phagocytosis
- Release of chemical messages
- Share info about microbes to T cells
What is the purpose of a dendritic cell in immune responses?
Links Innate and adaptive immune responses.
Phagocytic
Trigger adaptive immune responses
How do the cells of the immune system move around the body?
Carried in the blood and lymph, allowing them to leave and enter tissues.
Lymph in tissues collects and drains into lymph nodes
What is a PAMP?
Pathogen-associated molecular patterns.
Building blocks
What are the common building blocks of viruses?
Nucleic acids: ssRNA and dsDNA
What are the common building blocks of a bacteria cell wall?
Lipopolysaccharides (LPS)
Endotoxins
Lipoteichoic acid
What are the common building blocks of a bacteria flagellum?
Flagellin
What are the common building blocks of Bacterium nucleic acid?
Unmethylated CpG DNA
Describe pattern recognition receptors in a phagocytic cell
Receptors can either be on the outside or inside of a cell.
On the outside, they work to recognise bacterium and viruses on the cell membrane.
Within the cell, the phagolysosomes break down the bacteria and viruses into nucleic acids to recognise them.
All information is then sent to the nucleus of the cell
What is the purpose of fever/pyrexia?
Inhibits bacterial replication
Some features of the immune system work better at higher temperatures
What is the first step of the inflammatory response?
Chemical signals are released from resident cells to attract more cells to the injury site
What is the process of neutrophils in an inflammatory response?
Enter blood from bone marrow and cling to the capillary wall. They are then attracted to the site of the injury by the chemical trail.
What do the chemical signals from resident cells do during the inflammatory response?
Dilate blood vessels and make capillaries leakier, allowing neutrophils to get out.
True or false:
Myeloid cells are NOT phagocytic?
False
Describe the 5 stages of phagocytosis
Phagocyte recognises pathogen by adhering to it
Phagocytes form around the pathogen and forms a pseudopod, engulfing the particle and forming a phagosome.
Lysosomes fuse with the phagocytic cell.
Toxic compounds in the lysosome break down the pathogens.
Exocytosis sometimes removes the indigestable parts.
What happens when a lysosome and phagosome join?
A phagolysosome is formed because phagosomes do not have the right environment to break down and kill the pathogen or debris
Describe the killing and digestion of phagocytosed microbes
There is a low pH
Reactive hydrogen and nitric oxide intermediates
Enzymes
What are the 3 enzymes that break down pathogens in phagolysosomes?
Proteases
Lipases
Nucleases
Describe what happens during the complement cascade
A series of proteins that act in a sequence, allowing pathogens to be labelled and broken down
What are the 3 stages of the complement cascade?
Label pathogens
Recruit phagocytes
Destroy pathogens
Describe the process of opsonisation in the complement cascade
Pathogens are labelled so that they can bind to phagocytic cells and be uptaken during phagocytosis. This can either be through an antibody or a complement fragment of C3b.
Describe the process of chemotaxis during the complement cascade
Complement proteins are mediators and cause other phagocytes are recruited by sending out chemical signals, attracting them to the area of the injury. This is a process driven by C3a and C5a.
Describe the process of lysis during the complement cascade
Pathogens are destroyed through a membrane attack. Pores are formed in bacterial cells which results in their death, this is driven by C9.
What are the 3 complement pathways?
Classical
Alternative
Lectin
Describe the classical complement pathway
Antibody first binds to the pathogen and then to the complement
Describe the alternative complement pathway
Pathogen binds the complement to the pathogen component
Describe the lectin complement pathway
Carbohydrate component of microbes binds to the complement
What do all 3 complement pathways lead to?
C3 convertase amplification.
What 3 processes are the outcome of the development of C3 convertase
Label, destroy, recruitment.
What is the purpose of C3b?
Opsonisation
What process is driven by C9?
Lysis
What are C3a and C5a the drivers of?
Chemotaxis
What is the purpose of mast cells during recruitment?
C3a and C5a degranulate mast cells and the granules act as inflammatory mediators which attract more phagocytes to the area of the injury.
What are the 3 major cell communication methods?
-Cytokines or chemokines binding to receptors on membrane
-Cell surface receptors binding to surface-bound ligands
-Antigen presented to cell surface receptors
What are the 3 main methods of immune cell communication?
Cell membrane binding
Receptors and ligands
Antigen-presenting
Describe the process of chemical binding messengers
PAMP sends signals to the nucleus which can start or stop protein synthesis.
This is done by chemokine and cytokine
What is the purpose of cytokine?
Cytokine sends signals to the nucleus via transmembrane receptors
What is the purpose of chemokine?
Sends signals to the nucleus via transmembrane receptors and can also change how a cell moves.
What is an antigen?
Anything that is recognized by the immune system
Describe the process of activated dendritic cells communicating with T cells
Dendritic cells can make cytokines that bind with receptors on T cells
The surface bound receptors then join to ligands and present antigen to surface bound receptors
What do receptors connect to?
Ligands
What is an example of innate and adaptive immune responses interacting?
Activation of T cells by dendritic cells
What is a MHC?
Major histocompatibility complex
What is a TCR?
T-cell receptor
What are the 2 typed of MHC?
MHC-I presents intracellular antigen
MHC-II presents extracellular antigen
What MHC type is expressed on all nucleated cells?
MHC-I
What MHC type is expressed only on antigen presenting cells
MHC-II
What MHC type presents intracellular information?
MHC-I
What type of molecule is an interleukin?
Cytokine
What types of molecules stimulate cell migration?
Chemokines
Are chemo/cytokines produced by innate or adaptive immune responses?
Both
What do interleukins and interferons do?
Control the growth and activity of immune cells
How can T cells help B cells?
Making cytokine that bind to receptors on B cell membranes
Have surface bound receptors that bind to B cell ligands
What does the communication of T cells to B cells do?
Helps the B cell to make antibodies
What blood cells are involved primarily in immunity?
White blood cells (leukocytes)
What do dendritic cells do when they come across antigen/
Phagocytose the bacteria and then present parts to the spleen and lymph nodes.
What do dendritic cells do with peptides?
They break down the bacteria into peptides and present them via MHC to T cells
What do CD4 T cells do?
Help B cells make antibody
What do CD8 T cells do?
BEcome cytotoxic and kill virus infected cells
What is the purpose of antigen uptake in the innate immune response?
Clearance of pathogen
What is the purpose of antigen uptake in the adaptive immune response?
Presentation to T cells
What kind of immunity do invertebrates have?
Innate immunity
What kind of immunity do vertebrates have?
Innate and adaptive
How are endogenous antigens processed?
Antigens degraded into peptides in the cytoplasm by the proteasome, transported to the ER and loaded onto MHC-I
How are exogenous antigens processed?
Degraded in the phagolysosome
Loaded onto the MHC-II using the phagolysosome
How are antigenic proteins degraded into peptides?
Using a proteasome or an acidic phagolysosome
What are T cells and how do they arise?
Lymphocytes that develop in the bone marrow and fully develop in the thymus
What is the purpose of a T cell in adaptive immunity?
Recognise MHC and peptide complexes
True or false, proteins are all different in T cells
False, but they have different receptors
What are thymocytes?
Immature T-cells
What do thymocytes do in the thymus?
Rearrange the variable parts of their TCR genes and then get selected for
What are T cells that have not been activated by MHC called?
Naive
What are activated T cells called?
Effector T cells
What is the purpose of a CD4 helper cell? (3)
Recognises MHC-II/peptide
Helps CD8 T cell become cytotoxic
Helps B cell make antibody
What is the purpose of the Cd8 T cell? (2)
Recognise MHC-I/peptide
Develops into a cytotoxic T cell and becomes a killing machine
How do memory T cells work?
Memory CD4 or CD8 sit inside the body for long periods of time
What is the purpose of memory T-cells?
Become effector cells much quicker than naive T cells
What are the 4 main functions of B cells?
Lymphocytes that develop in bone marrow
Express unique antigen receptors
Plasma cells are activated B cells
Memory B cells provide memory
What can B cells differentiate into?
PLasma cells
Draw a diagram of a B cell receptor
(B cells and antibody)
How many BCR are on 1 B cell?
Around 100,000
What is BCR?
B cell receptor that binds antigen and activates B cell
What is BCR anchored by?
Transmembrane domain and secreted by antibodies
What are the 3 functions of antibody?
Neutralisation
Opsonisation
Complement activation
Describe neutralisation
Effective neutralises toxins and stops them from latching onto our cells
Describe opsinisation
To make tasty to phagocytes
What is complement activation in terms of antibody?
Antibody complements through the classical pathway
What are the yellow structures on a globular protein called?
Epitopes
What is the purpose of an epitope?
Footprints where antibodies can bind
What is native antigen?
The antigen does not need to be processed to a peptide
What are the 5 classes of immunoglobulin?
IgG
IgA
IgM
IgE
IgD
What is the distribution of IgG?
Abundant
What is the and distribution of IgA?
Present in secretions
Monomeric in blood
What is the function of IgG?
Opsinises/neutralises
Crosses placenta
Targets virus/bacteria
What is the function of IgA?
Defense of mucous membranes
Confers passive immunity
Targets virus/bacteria
What is passive immunity?
PAssing immunity on to infants via nursing
What class of immunoglobulin has passive immunity?
IgA
What is the distribution of IgM?
First class expressed after initial exposure
Expressed in B cells
What is the function of IgM?
Activated complement
Targets extracellular bacteria
Acts as BCR
What is the distribution of IgE?
Present in low concentrations
What is the function og IgE?
Immunity to multicellular parasites
Allergic reactions
What is the distribution of IgD?
Expressed on naive B cells
What is the function of IgD?
Acts with IgM
How long does the primary immune response take?
7-14 days
How much antibody is produced during the primary immune response?
Relatively low
What does the secondary immune response rely on?
B cells
How fast is the secondary immune response?
2-3 days
What is the main immunoglobulin produced in the secondary immune response?
IgG, switching to IgA and IgE
What is the main immunoglobulin in the primary immune response?
IgM
What is SCID?
Severe combined immunodeficiency
How is SCID caused?
X-linked disease, patients lack functioning T and B cells
How does HIV impact CD4 cells?
Kills them which means that the cells cannot provide help for antibody
How does measles impact the immune system
Can erase immune system memory
What is autoimmune disease mediated by?
Adaptive immune response
What is immune tolerance?
Thymus deletes autoreactive T cells
What can failures in immune tolerance called?
Autoimmunity
How is arthritis caused?
When autoreactive T and B cells attack self antigens in the joints
How is type I diabetes caused by the immune system?
Beta-cells attacked, meaning that insulin cannot be produced
What is the effector response to an allergic reaction?
Allergen detected, T cells activate B cells which secrete IgE. The IgE binds to mast cells (FcR) causing degranulation and release of histamines
What are the order of events in changes of anti-body structure?
Rearranged in bone marrow, and then constant region is switched during immune response (see errors in immunity)
What order is the immunoglobulin class switch?
IgM/D - IgG - IgA - IgE