Immunology Flashcards
What are the organs of the immune system?
Thymus- located behind breastbone, T-cells mature
Bone Marrow- Create WBCS
Lymph Nodes- produce and store cells which fight infection and disease
Spleen- Contains WBCS
What is the lymphatic system?
Links key organs
Purpose of lymphatic system
-transport clean fluids back to blood
-drain excess fluid
-removes debris from cells of body
-transport fats from digestive system
What is the difference between innate immunity and adaptive immunity?
Innnate immunity is the first line of (non specific) defence whilst adaptive immunity is specific and acquired
What are the three components of innate immunity?
-epithelium (physical barrier)
-innate cell subsets & complement
-Chemokines/cytokines
What is the difference between chemokines and cytokines?
Chemokine-signalling molecule
Cytokine-Cell activation/proliferation
What are the 2 cell types in adaptive immunity?
B cells
T cells
What is adaptive immunity?
Provides neurological memory to fight infections again, 4-6 days
What is inflammation?
Inflammatory reaction is aimed at eliminating inciting cause eg foreign agent
What are examples of foreign agents?
-Invading microorganisms
-particulate material ( dentures, dust)
-altered self cells
What are stages of an inflammatory response?
Initiation, response to harmful agent
Progression, containment of harmful agents
Amplification, modulation of immune response
Resolution, healing
Eg of acute inflammation and severe inflammation?
Gingivitis and Periodontitis
What is innate immunity?
The first line of defence against pathogens
What are commensal organisms?
Organisms which don’t cause disease
When does the innate immune response occur?
Between 1-4 days
What is non-specific immune system driven by?
Innate
How is the innate immune system effective?
Regular contact with the potential pathogens which are destroyed within minutes or hours, rarely causing disease
How does epithelium present innate immunity?
Produces antimicrobial peptides
Produces cytokines/chemokines
How does innate cell subsets present innate immunity?
Phagocytic cells
Antigen presenting cells
What compounds do epithelium in the oral cavity produce?
Antimicrobial peptides
Immunoglobins
Lactoferrin
Lysosome
Cystatins
What is the function of antimicrobial peptide?
To kill microbes (binding to cell wall, attaching to surface and disrupt membrane) and modulate the immune system.
What is an example of an antimicrobial peptide?
B-defensins
Human neutrophil peptides
Cathelicidins
Psoriasin proteins
What is the function of the secretory immunoglobin?
Form a protective layer in saliva, preventing pathogens from attaching to epithelium
What is lactoferrin?
Glycoprotein that transports iron ions
but has antimicrobial activity. Present in saliva and
produced by neutrophils.
What is lysozyme?
Present in saliva and produced by
macrophages/neutrophils. Targets cell walls of
bacteria.
What is cystatins?
Anti-protease activity and supports remineralization of the teeth
How do host cells recognise microbes?
Cells involved in immune responses have receptors for components of microorganisms ANTIGENS
What is the main receptor that recognises microbes and where are they present?
Toll-like receptors
They are present on the surface plasma membrane or inside the cell.
Toll-like receptors present on cell membrane will recognise what?
Bacteria and fungal pathogens
Toll-like receptors present inside cell will recognise what?
Viruses
What are other types of receptors other than toll-like?
– Dectin and glucan receptors – Fungal recognition
– NOD-like receptors – Bacterial recognition
– Protease-activated receptors (PARs) - Microbial and allergen recognition
What are cytokines?
Signalling molecules that orchestrate immune responses.
What are the different functions of cytokines?
-Autocrine – alter behavior of cell
from which they were secreted
e.g., self-regulating
* Paracrine – alter behavior of
neighboring cells
* Endocrine – enter circulation and
alter behavior of distant cells
What are chemokines?
They tell cells where to go
What are chemotaxis?
Chemotaxis is the movement of a cell in a direction
corresponding to a gradient of increasing or decreasing
concentration of a particular substance (e.g., chemokines).
What is the main morphological change associated with dental caries?
Tooth decay
Where do all myeloid and lymphoid cells originate from?
In the bone marrow from a hematopoietic stem cell
Where do T cells mature?
Thymus
Innate immunity is the first line of which type of defence?
Non specific and effective
Adaptive immunity is the first line of which type of defence?
Specific and long lived
What is an example of a disease failing to resolve itself?
Chronic inflammation
What defence cell circulates in the blood and are precursors for macrophages?
Monocytes
When mast cells degranulate what do they release?
Histamine
What do neutrophils produce in order to encapsulate microbial cells?
NETS
What is the main role of dendritic cells?
Antigen presentation
Where is the site of dendritic cell- T cell interaction?
Lymph nodes
What is responsible for driving T cell differentiation?
MHC Proteins
What is the main role of B cells?
Production of antibodies
Epithelial cells, endothelial cells and fibroblasts are examples of what type of immune cell?
Non- professional immune cells
What is the name of the antibody produced at the epithelial surface and found in saliva?
Secretory Immunoglobin
B defensins and cathelicidins are examples of what?
Antimicrobial Peptides
The components of microbial cells that elicit an immune response are called?
Antigens
Dectin and glucan receptors are examples of PAMP’s which recognise what?
Components of fungus
Cytokines which alter the behaviour of neighbouring cells can be described as?
Paracrine cytokines
What are chemokines primarily responsible for?
Recruitment
Why is cytokine/chemokine balance essential?
For optimal effectiveness
What do neutrophil granules contain?
Degradative enzymes and microbial substances
What do neutrophils attract to sites of inflammation?
IL-8
What are cell adhesion molecules?
Cells which control interactions between immune cells and endothelial cells
What are the three main families of cell adhesion molecules?
Selectins
Integrins
Immunoglobin superfamily
What is the importance of cell adhesion molecules?
Immune trafficking
What is the primary function of neutrophils?
Engulf and destroy evading pathogens
What is chromatin?
Clump of nucleic acids
What does activation of NETs stimulate neutrophils to do?
Release proteins and some genetic material (chromatin) to form extra cellular fibril matrix
What do M1 and M2 macrophages do?
M1 -proinflammatory cytokines
M2- Inflammatory cytokines
What is the primary function of macrophages?
Phagocytosis and presentation of antigen to adaptive immune cells
What are the two types of antigen presenting cell?
-Non-professional (Epithelial cells/fibroblasts/endothelial cells)
-Professional (Macrophages and dendritic cells)
What are granules and what may they contain?
Vesicles containing preformed mediators; eg
Proteinases
Antimicrobials
What is essential for the link between innate and adaptive immune system?
Phagocytosis and antigen presentation
What are the 4 enzymatic cascade systems of plasma?
Complement
Kinins
Coagulation factors
Fibrinolytic system
What is ‘complement’?
Collection of soluble proteins present in circulation of plasma which drives inflammation or opsonisation
What is oponisation?
Coating of pathogens by antibodies or complement proteins
What are the 3 pathways of ‘complement’?
(1)Classical pathway – antibody attached to microbe
(2) Alternative pathway – microbial cell wall
(3) Mannose binding lectin pathway (MBL) – carbohydrates on pathogen surface
What are the functions of analphylatoxins?
Contraction of smooth muscle
Capillary leakage
What enzymes are involved in the 3 pathways of ‘complement’?
C3 and C5 Convertase
What are analphylatoxins?
Glycoproteins such as complement components C3, C4 and C5 (and their fragments) that drive immune responses
Produced by mast cells
What immune responses to anaphylatoxins drive?
-Promote immune cell recruitment
-Increase adhesion of cells to vessel walls
-Induces granulation
-Promotes cytokine production
-Induces antigen presentation
-Regulate adaptive immune responses
What is the function of T cells?
Drive cell-mediated immunity
What is the function of B cells?
Produce antibodies and drive humoral immunity
What is meant by humoral?
Anything produced by cells i.e. antibodies
What are the three main receptors involved in adaptive immunity?
-t cell receptors (TCR)
-B cell receptor (Immunoglobulins[Ig])
-Major histocompatibility complex (MHC proteins)
Where are T cells derived from and where do they mature?
Bone marrow and thymus
What do all T cells start as?
Naïve T cells
What does the variable region of t cell receptors contain?
Antigen binding site
What are the genes rearranged by in T cell receptors?
Somatic recombination
What is somatic recombination driven by?
RAG (Recombinase) enzymes
Why is thymic education important?
To stop T cells responding to peptides in own body
Where are the T cell receptors arranged?
Thymus
What is positive selection of the T cell?
No recognition= apoptosis (cell destroyed)
What is negative T cell selection?
Recognition of self antigen= apoptosis
What do T cells interact with in the thymus?
Thymic cortical epithelial cells
Explain the three signals required to activate T cells
.
Function of TH1 cells?
Support macrophage function, by making lots of interferon-gamma
Main function of TH2 cells?
Produces lots of interleukin-4, 5 and 6 which instruct B cells to produced antibodies
Main function of TH17 cells?
Produce interleukin 17 and 22 which enhances clearance of extracellular bacteria and fungi
Function of T follicular helper cells?
Work with B cells for antibody production
What is the main function of Treg cells?
Release inhibitory cytokines ( interleukin 10)
Inhibit T cell activation and dendritic cell activation
What are CD8+ cells driven by?
MHC 1 molecule, found on all cell types
What enzymes do cytotoxic T cells produce?
Granzyme and perforin
What is the function of perforin?
Facilitate granzyme entry into infected cell, once in cell causes apoptosis
What are the five different type of immunoglobins produced by B cells?
IgG
IgE
IgD
IgM
IgA
Functions of the five classes of immunoglobins!!!!
How many subsets does IgG have?
4
What is the difference between T cell and B cell receptor structure?
T cell have alpha and beta chains
B cell receptors have heavy and light chains
Where do B cells develop?
Bone marrow
What do the heavy chains involve in B cell receptors?
Rearrangement of Variable (V), Diversity (D) and Joining (J) genes
What do the light chains involve in B cell receptors?
Rearrangement of Variable (V) and Joining (J) genes
What is the main immature B cell receptor?
IgM
What immunoglobins do mature B cells express on the surface?
IgM and IgD
Where do B cells undergo negative selection?
Bone marrow
What will happen to self reacting B cells?
Macrophages engulf any self-reacting B cells
What are the three main functions of antibodies?
Neutralization
Opsonization
Initiation of complement
What is opsonisation?
The coating of pathogens by antibodies or complement proteins
-phagocytosis
-Antibody dependant cellular cytotoxicity (ADCC)
-Mast cell degranulation
What are the 2 B cell receptors?
IgD and IgM
Until when are B cells still known as naive?
Until they come in contact with an antigen
What two ways can B cells be activated?
Involving T cells- Thymus-dependant antigens
Thymus-independent antigens
What does the activation of naïve B cells result in?
The rise of plasma cells
What are plasma cells?
Antibody factories
What is the first cells produced when a naïve B cell reacts with an antigen?
IgM
What is the affinity for an antigen?
The strength of a binding to an antigen
What is meant by the avidity of an antibody?
Ability of antibodies to form complexes
