Immunology Flashcards
What is the immunesystem
A complex orchestration of molecules, cells, tissues and organs to protect against:
Microbial pathogens including bacteria, viruses, parasites
Tumor cells
What are the two lines of defence
Innate, first line of defence
Adaptive, second line of defence
What is active immunity vs passive immunity
Active: antigens enter body and trigger immune systems, provides long term protection
Passive: antibodies pass from mother to:
Foetus across the placenta,
Infant in breast milk
Provides short term protection
What is the role of a neutrophil
Principle phagocytic cell of innate immunity
Rapidly migrate to infection site, ingest microbes by phagocytosis, release oxygen free radicals, degranulate releasing proteins with microbicidal properties
What is the role of the eosinophils
Important defender against multicellular parasites and have a role in allergy and asthma
What is the role of the basophils
Involved in inflammatory allergic reaction
Release histamine
What is the role of moncytes
Circulate in blood, bean shaped nuclei, precursors of tissue macrophages
Effectors of inflammatory response to microbes
Kills pathogens via phagocytosis, free radical production, myeloperoxidase and inflammatory cytokines
What is the role of macrophages
Derived from blood monocytes
Participate in innate and adaptive immunity
Phagocytosis, microbicidal mechanisms, antigen presentation to other cells
What is the role of the dendritic cells
Process and present antigens on their cell surface to T-lymphocytes to initiate specific immune responses
What is the role of the mast cell
Similarities with basophils, release histamine, close association with allergy and inflammation
What are B-lymphocytes
Produce antibodies
Present antigens to other cells
Can produce long lived memory cells
Need two signals to be activated: antibody/antigen interaction acne other T-cells or inflammatory mediators
What are T-lymphocytes
Plays critical role in development and regulation of cell mediated immunity
Influences the activities of other cells
Able to kill virally infected and tumour cells
Generate long lived memory cells
What are natural killer cells
Generally considered part of the innate immune response
Release cytokines (IFN-y and IL-2) and granzymes and trigger apoptosis in target cell
Kill infected cells which do not express foreign surface antigen
Respond rapidly
Involved in tumour immunosurveillance
Where is the primary lymphoid tissue and what happens there
Bone marrow: b-lymphocytes
Thymus gland: t-lymphocytes
Development and maturation of lymphocytes
Where is the secondary lymphoid tissue and what happens there
Lymph nodes, spleen, tonsils, appendix, adenoids, Peyer’s patches in ileum, bronchial associated lymphoid tissues
Mature lymphocytes encounter antigens/pathogens
What are key components of innate immune system
Mechanical barriers: skin and mucus membrane
Physiological: stomach acid and fever response
Chemical mediators: plasma proteins
Phagocytic leukocytes
Natural killer cells
What are the two types of adaptive immune system
Humoral immunity mediated by antibodies produced by B lymphocytes
Cell-mediated immunity effected by T lymphocytes
How does a vaccination work
Exposure to antigen -> activation -> clone formation -> formulation of plasma cells and memory cells -> Plasma cells secrete antibodies into circulation -> memory cells store information until the next exposure to the same antigen
What are the 5 types of immunoglobin and what are their roles
IgM IgG IgA IgE IgD
What are the roles of IgM
Main antibody of primary response, best at fixing complement, monomer form serves as B cell receptor
What are the roles of IgG
Main blood antibody of secondary responses
Neutralizes toxins
Opsonization
What are the roles of IgA
Secreted into mucus, tears, saliva, colostrum
What are the roles of IgE
Antibody of allergy and anti parasitic activity
What is the role of IgD
B cell receptor
How do antibodies work
Label invading organisms to be destroyed by other parts of immune system, this is opsonisation
What is the major histocompatibility complex
Inherited
T cells only recognise antigens as complexes with MHC molecules
Peptides are presented on the surface of of antigen presenting cells in association with the MHC
Allows immune cells to discriminate between normal antigens and foreign ones
What are MHC class I molecules
Present on almost every cell in the body
Present endogenous antigens that are synthesised in the cytoplasm on the surface
Displayed to cytotoxic T cell lymphocytes (CD8+)
If foreign the cell is killed otherwise it is spared
What are MHC class II molecules
Only present on specialised antigen-presenting immune cells: macrophages, dendritic cells and B cells
Present exogenous antigens that originate extracellularly from foreign bodies
This is recognised by helper T cell lymphocyte (CD4+)
The binding stimulates development of antibody-producing B cells against the antigen
What are the types of immune system disorders
Autoimmunity
Hypersensitivity reactions
Immunodeficiencies
What is the function of the complement cascade
Membrane attack complex produced to stab at invading pathogens
Produce anaphylatoxins
Prime pathogens for phagocytosis by macrophages and neutrophils (opsonisation)
What are the three types of complement activation pathways
Classical
Lectin or mannose-binding
Alternative
What is the classical pathway
Activated by antigen-antibody complexes
Complement factors are serine proteases
Limited proteolysis
What is the Lectin or mannose-binding pathway
Involves mannose-binding lectin which binds sugars (mannose) found on the surface of pathogens but not on mammalian cells
MBL binds with MASP 1 and 2 which activate C2 and C4, rest of pathway is as it was in classical
What pathogens trigger the mannose-binding pathway
Yeast such as Candida albicans
Viruses such as HIV and inluenza A
Bacteria including Salmonella and Streptococci
Parasites such as Leishmania
What is the alternative pathway
Involves auto-activation of C3 to C3a and C3b which occurs constantly at a very low rate
Upon contact with bacteria auto-activated C3b binds factor B and properdin which rapidly activates more C3 and activates C5
What are the anaphylatoxins
C3a, C4a and C5a
By-products of C3-5 during complement activation
Trigger degranulation of endothelial cells, mast cells and phagocytes
Cause smooth muscle contraction and enhance vascular permeability
C3a and C5a also act as chemoattractants; they attract and activate neutrophils
What is opsonisation by C3b
C3b renders bacteria more susceptible to phagocytosis
C3b is cleaved to iC3b on the bacterial surface
The macrophage cell membrane contains receptors for iC3b, facilitating phagocytosis of the bacteria by the macrophage
What are the roles of the hyperactive macrophages
Become hyperactive when stimulated by IFN-y and lipopolysaccharide (LPS) produced by gram-negative bacteria
Hyperactive macrophages stop proliferating, become larger and increase they rate of phagocytosis
Hyperactive macrophages produce cytokines: tumour necrosis factor (TNF) which can kill tumour cells and virus-infected cells, and interleukin-1 (IL-1)
What are the three stages of macrophage activation
Resting
Primed
Hyperactive
What is produced as a result of B-cell maturation
B-cell matures into plasma cell which allows for production of large quantities of antibody
What cells can present antigens to T-cells
Monocytes
Macrophages
B cells
Dendritic cells
What are the three types of T-cells
Helper: Activate B cells, activate phagocytes and help other T cells
Killer: cytotoxic T lymphocytes, effective at attacking viruses
Regulatory: not fully understood, regulate against self destruction
What are the CD3 CD4 and CD5 molecules
CD3 is associated with T cell receptor to make the CD3/TCR complex
CD4: helper
CD8: cytotoxic
What is MHC and its two types
Glycoprotein present on cell surfaces that help differentiate self from non-self
Plays crucial role in T cell activation
MHC II (helper) MHC I (cytotoxic/ killer cells)
What are the Th1 and Th2 cytokine roles
Th1: activate cell mediated immunity
Th2 are responsible for antibody production
What is autoimmune disease
Occurs when self tolerance against a body antigen is broken
What are examples of autoimmune conditions
Organ specific: Thyroid disease Type 1 diabetes Pernicious anaemia Some skin conditions
Non-organ specific:
Systemic lupus erythematosus (SLE)
What is anergy
T- cells become temporarily unresponsive to all signals due to lack of co-activation
