Introduction to Immunology Flashcards
What is clinical immunology?
The study of the function of the human immune system
What does an effective immune response involve? (general)
Recognition.
Specificity.
Response.
Memory.
What are the 4 classes of pathogens ? (+examples)
Viruses
e.g. SARS-CoV-2, influenza, poliovirus, HIV
Bacteria
e.g. Staphylococcus aureus, Mycobacterium tuberculosis, Vibrio cholerae
Fungi
e.g. Candida albicans, Tinea corporis, Cryptococcus neoformans
Parasites
e.g. Trypanosoma, Leishmania, roundworms, tapeworms
How are pathogens recognised as non-self?
Due to posession of antigens
Macromolecules that are structurally different to those of human host
PAMPS
= pathogen associated molecular patterns
What are the (6) categories that make up the immune system?
Cells
= B , T, neutrophils, macrophages, ILCs, DCs
Molecules
= antibodies, complement proteins, cytokines, cell surface receptors
Primary lymphoid organs
= bone marrow, thymus
Secondary lymphoid organs
= lymph nodes, spleen
Peripheral Tissues
Systems
= circulatory, lymphaticsc
What are some cells that contribute to the immune system? (+ their roles)
Phagocytes
e.g. neutrophils, macrophages
= recognise, engluf and destroy microbes by phagocytosis
B cells
= differentiate into antibody-secreting plasma cells
T cells
= differentiate into cytotoxic T cells to kill virus infected host cells
= differentiate into helper T cells to assist B cell differentiation
Dendritic cells
= immune surveillance and activation
= collect and present foreign antigens to activate adaptive immune system
What are the types of Immune Responses?
Innate
= rapid first line of defence
Adaptive (acquired)
= specific, effective , memory
Humoral
Cell-mediated
Give an overview of the humoral and cell-mediated branches of the immune system?
What is the purpose of recognition molecules? (+ examples)
For the immune system to recognise pathogens
e.g. cell surface receptors, antibodies
How can recognition molecules be encoded? (+examples)
Encoded by normal genes inherited from parents (germ line)
= e.g. receptors of the innate immune response
Encoded by genes created during life by random DNA rearrangements
= e.g. B and T cell receptors and antibodies of the adaptive immune response
How does recognition operate?
Via signalling pathways
e.g. lymphocyte signalling
What (3) classes does innate immunity involve?
Physical Barriers (e.g. skin)
Chemical Barriers (e.g secretions)
Immune responses
What is an inflammatory response? (INNATE)
When immune cells, molecules and fluid are attracted to the site of infection
What do complement components do? (INNATE)
Bind to the surface of microbes
= causing their lysis
What do cell surface receptors recognise? (+where are they found)?
Found on cells like macrophages, natural killer (NK) cells
Recognise specific molecules on microbe surface
= PAMPs
Known as PRRs = pattern recognition receptors
What does binding of PAMPs trigger?
PAMPs bind to PRRs
= triggers response such as phagocytosis (macrophages) or killing (NK cells)
What does adaptive immunity rely on?
Recognition by cell surface receptors, B and T cell receptors
Randomly generated by DNA rearrangements during B and T cell development
What is clonal selection?
The binding of antigen to an individual B or T cell cell that then stimulates proliferation of that cell producing a population with identical antigen specificity.
What do only a small minority of BCR and TCRs do?
Bind to their specific antigens and go on to participate in immune responses.
Despite a huge diversity of BCR and TCRs being continuously produced.
What does activation of naive T cells result in?
The production of a range of different effector and memory T cells
(depending on the nature of the stimulating antigen)
Why do memory B / T cells persist after infection has subsided?
For a quicker / more effective adaptive response upon re-exposure to the same pathogen.
= underpins effectiveness of VACCINES
Summarise Properties of Innate vs Adaptive Immunity
Properties:
Speed
Specificity
Diversity
Memory
Self / Non-self discrimination
Major cell types
What is hematopoisesis?
How cells of the immune system are produced and develop.
Where do the cells originate + progress?
From the hematopoetic stem cells in the bone marrow.
progress through various differentiation pathways, making choices + become progressively committed to becoming a particular type of immune cell
Where does differentiation begin + where is it completed?
Begins in the bone marrow.
Can be completed in bone marrow or matured in the secondary lymphoid tissues / peripheral tissues.
What is the thymus? What happens there?
It is a specialised immune organ.
This is where T cells mature before dispersal elsewhere.
What are the primary lymphoid organs?
Bone marrow.
Thymus.
What happens in the bone marrow?
B lymphocytes develop in contact with the stromal cells of bone marrow.
What do stromal cells facilitate?
HSC proliferation.
Direct migration.
Stimulate differentiation.
What happens in the Thymus?
T cells develop initially in the bone marrow BUT then migrate to the thymus to achieve full maturity.
What does the microenvironment of the thymic cortex and medulla do?
Directs stepwise changes in thymocytes.
What does TCR affinity of binding with MHC-peptides do?
Drives positive and negative selection.
What are the secondary lymphoid organs?
What happens there?
Lymph nodes.
Spleen.
Where B cells and T cells encounter antigen , become activated , expand in numbers and differentiate into effector cells.
What are lymph nodes? (+cells involved)
Highly organised bean-shaped structures packed with B cells, T cells, macrophages and dendritic cells.
What do lymphatics do?
They bring antigens from tissues to the lymph nodes.
What does the spleen do?
Performs a similar function as the lymph nodes against blood-borne pathogens.
= first line of defense against bloodborne pathogens
What is the MALT - mucosa-associated lymphoid tissue?
A large, dispersed and important lymphoid tissue sited to protect vulnerable mucosal surfaces: gut, lungs, nasal passages.
What is the structure / function relationship of Lymph nodes?
B / T cell activity is seperated into distinct MICROENVIRONMENTS
= B - cortex
= T - paracortex
Medulla
= contains macrophages and dendritic cells
Antigens
= enter via afferent vessel
Naive lymphocytes
= enter via HEV (high endothelial venule)
= lymphocytes exit via efferent vessel
What is the structure / function relationship of the spleen?
RBCs
= compartmentalised in the red pulp
WBCs
= segregated in the white pulp
Marginal zone
= specialised region of macrophages and B cells that borders the white pulp
What is the structure of antibodies?
Heavy Chain
= effector activity
Light Chain
= antigen binding
Hinge
What are some examples of antibody types?
IgG (1-4)
IgD
IgE
IgA
IgM
What is the CD (cluster of differentiation) system in B cell receptors?
Unified nomenclature for describing immune-associated surface molecules
What do T cells need to be able bind an antigen?
Antigen must be presented by an APC - antigen presenting cell
e.g. macrophage, dendritic cell
How does APC present antigen? What are the 2 classes, what do they require?
via a MHC - major histocompatibility
MHC Class I
= requires CD8 co-receptor
MHC Class II
= requires CD4 co-receptor
What are cytokines?
Small protein messengers.
Used to send signals between immune cells and generate response by signal transduction
E.g. IL-1, TNF-alpha
What characteristics do cytokines show? What can they initiate?
Redundancy.
Pleiotropy.
Synergy.
Antagonism.
= can initiate downstream signalling cascades.
What are cytokines essential for? What can they cause in their target cells?
The proper function of the immune system.
= can cause differentiation, proliferation or apoptosis in their target cells.
What are chemokines?
Similar to cytokines.
BUT = cause movement of target towards source of the chemokine
e.g. CCL1, CXCL2
What are the 3 types of immune dysfunction? (+examples)
Overactive
= e.g. asthma, allergies, immunopathology
Misdirected
= e.g. autoimmune diseases
Unresponsiveness
= e.g. immunodeficiencies
Give examples of immunological changes?
Malignant Cancer
= cancer not recognised as it is ‘self’
Organ Transplantation
= transplanted organ identified as foreign , ‘non-self’, will be rejected.
