Innate + Adaptive Immunity Flashcards
What are the (4) roles of the immune system?
- Immunity to infection
- Inflammatory processes
- Removal of senescent cells
- Defence against neoplasia e.g. cancer
What is the medical relevance of Immunology?
Immune disorders
Immunology tests
Immunotherapies
Immunoprophylaxis
What general immune disorders are there?
Immunodeficiency - primary (birth) + secondary (later in life)
Hypersensitivity (allergy, anaphylaxis)
Autoimmunity - failure to distinguish self from non-self
What general immunology tests are available?
- Serology - antibody detection after infection
- Cellular response to infection e.g. tuberculin skin test, interferon gamma release assay)
- Diagnosis of hypersensitivity + AI
- Cross matching + tissue typing
What general immunotherapies are available?
- Immunodeficiency - transfusion of ABs from extracted blood
- Hypersensitivity - de sensitisation via slow gradual exposure
- Anti TNF drugs for autoimmunity
- Infection (IFN for chronic HCV infection)
- Cancer e.g. IL-2 for melanoma + renal cancer
- Transplantation
What method(s) of immunoprophylaxis exist?
Vaccination against infections + some cancers
Define the term ‘Antigen’
Any substance capable of inducing a specific immune response i.e. targets of immune system
What are ‘self-antigens’?
Molecules usually tolerated/ignored by own immune system
What can differentiate antigens from host molecules?
Pathogen-associated molecular patterns (PAMPs)
What components can the immune system be divided into?
Innate + Adaptive
Antigens with PAMPs mostly targeted by innate mechanisms, other antigens targeted by adaptive
List the components/differences of innate + adaptive immune system
Innate:
- primary line of defence
- immediate response
- no clonal selection (same response every time)
- no immunological memory
- no antigen presentation
- recognises certain threats
- complement
- first point of innate epithelial barriers
- natural killer cells for if antigens are inside cells e.g. virus
Adaptive:
- secondary line of defence
- delayed response
- recognises all threats
- antigen presentation
- clonal selection (clones of cells that best tackled Ags)
- immunological memory (quicker, specific response in future)
- only 1 receptor on each B lymphocyte specific for Ag
Which immune cells are involved in innate immunity?
Epithelial barriers Neutrophils, eosinophils, basophils (Phagocytes) Dendritic cells NK cells Complement
Which immune cells are involved in adaptive immunity?
B lymphocytes - plasma + memory cells T lymphocytes - cytotoxic, memory, helper, suppressor Antibodies Effector T cells Monocytes + Macrophages (phagocytes)
What is the difference between monocytes and macrophages?
No difference! Same cell just different name depending on where they appear. Monocytes = within cells, Macrophages = outside cells
What role do eosinophils have?
Associated with parasitic infections + allergic responses - filled with granules that release histamine + other mediators
What role do basophils and mast cells have?
Inflammatory + hypersensitivity responses
What are mucosa associated lymphoid tissue?
MALT = adenoids + tonsils
What is the role of the thymus?
Site for T lymphocyte maturation before birth
What is found in bronchus associated lymphoid tissues?
Macrophages (sit in airways waiting for antigens)
What are some of the components of the Lymphatic System?
Adenoids, tonsils, L+R subclavian vein, lymph nodes, BALT, kupffer cells, spleen, Peyer’s patches, appendix, bone marrow, lymphatics
What humoral factors exist?
Acute Phase proteins
Complement
Antibodies
Cytokines
What are acute phase proteins? What is their role?
α, β, γ-globulins e.g. CRP
Innate humoral immunity, primitive poorly effective responses
What is the complement cascade? What is its role?
β-globulins
Innate humoral immunity, 2 stages of pathway (classical + alternative).
When triggered they will form channel (membrane attack complex) which punches holes in foreign cells
What are antibodies? What is their role?
γ-globulins
Adaptive humoral immunity
First produced = IgM followed by IgG (IgA, IgE, IgD + some sub-types made in different situations)
What are cytokines? What is their role?
Many proteins, control immune system
Examples = interleukins, TNF, interferons, CSFs
Up regulate immune system, chemotaxis, viral resistance
Describe/draw the basic unit of antibody structure
Y shaped structure with a heavy and light chain. Light chain on tails of Y, with an antigen binding site on both ends of the Y.
Darker zones = functional component, same for every AB
Lighter zones = specific component
What are the 5 different classes of antibodies?
IgM - 1st produced, 5 subunits IgG IgA IgD IgE
Most infectious agents are prevented from entering the body by…
Barrier Immunity
What are the different types of barriers to infection?
- Physical - skin, mucus, respiratory cilia, commensal organisms
- Biochemical - skin sebaceous secretions, lysozyme in tears, spermine in sperm, gastric acidity
What are the common sites of infectious agents access?
Enter via mucosal surface of: nasopharynx respiratory tract alimentary tract (GIT) genito-urinary tract
What is phagocytosis?
Recognition + engulfment of microbes which are then killed by the release of toxic chemicals into the enclosed vacuole
What 2 different cell types are involved in phagocytosis?
Polymorphonuclear (PMN) leukocytes = neutrophils, eosinophils, basophils
Mononuclear phagocyte system (MPS) = monocytes + macrophages
What are the stages of phagocytosis?
- Chemotaxis + adherence of microbe to phagocyte
- Ingestion of microbe by phagocyte
- Formation of phagosome
- Fusion of phagosome with lysosome containing digestive enzymes to form phagolysosome
- Digestion of ingested microbe by enzymes
- Formation of residual body containing indigestible material
- Discharge of waste materials
What are NK cells?
Natural Killer cells = lymphocytes that perform both direct + antibody-dependent cell cytotoxicity (innate immunity), all express CD56 on surface.
Detect MHC Class I changes through lack of stimulation of inhibitor receptors leading to activation
What is normally expressed on healthy human cells (except RBCs)?
MHC Class I molecules - these are lost in infected/malignant cells
Why is CRP a useful marker in clinical practice?
C reactive protein = an acute phase protein in blood that binds to surface molecules of bacteria + fungi but not viruses and has some inhibitory effects + promotes complement binding.
Useful marker therefore of bacterial infection.
What is MHC? What is the difference between MHC Class I and II molecules?
MHC = major histocompatibility complex (same as human leukocyte antigen (HLA) system)
MHC Class I found on all human cells except RBCs - presents host, viral or neoplastic antigens to Tc lymphocytes
MHC Class II found only on antigen presenting cells - presents ingested microbial Ags to Th lymphocytes (interaction with B lymphocytes to produce ABs)
What is the interaction of MHC and T cell receptors called?
MHC restriction
How is tolerance to self-Ag achieved?
Essential and seems to rely on pre-natal exposure + continuous/large-scale re-exposure to own Ags
What are stimulating and inhibiting factors within the IS?
Stimulating factors = presence of Ag, Th cells, cytokines
Inhibiting factors = removal of Ag, Tc cells, cytokine breakdown
Describe the process of clonal selection
T and B lymphocytes with best fit multiply + evolve (receptors change + alter with the ones that perfectly fit Ag kept and multiplied) then repeat
What is the difference between primary adaptive response and secondary response?
Primary = 5-10 days, relatively small peak response, lower affinity, more variable ABs, usually IgM>IgG
Secondary = 1-3 days, larger peak response, higher affinity, relative increase in IgG and under certain situations IgA or E
How + where does Immunological T cell tolerance occur?
- Negative selection - deletion of tissues that theoretically would target own tissues before birth
- Development of regulatory T cells - T cells that would normally cause harm are developed + regulated so will not harm self as told they were there from birth
Occurs in thymus
What are interleukins? What do they do?
12 different proteins
Produced by MPS + Th cells
Stimulate various components of immune system leading to proliferation, differentiation, activation + chemotaxis
Involved in every step of adaptive NOT innate
Short-lived autocrine + paracrine effects
What is TNF? What does it do?
Tumour necrosis factor
small protein produced by MPS cells has multiple effects e.g. fever, inflammation, enhanced immunity, septic shock, anorexia, cachexia
- reason for weight loss with cancer
- unregulates IS but lots of damaging side effects
What are interferons? What do they do?
3 different proteins produced by virus-infected and T-helper cells
Activate NK and T-cytotoxic cells leadings to cell cytotoxicity + other host cells virus-resistant. Also activate macrophages + up regulate Ag presentation
