Immunology Flashcards
Define immunity
State of possessing sufficient biological defenses to provide protection from invading pathogens
What kind of diseases are caused by an overactive immune system?
Allergies and autoimmune diseases
What are the primary lymphoid tissues?
Bone marrow and thymus
What are the secondary lymphoid tissues?
Spleen, tonsils, lymph nodes
What is the structure and function of the spleen?
White pulp - Maturation of WBCs (B/T lymphocytes)
Red pulp - Breakdown of RBCs, rich in macrophages
Capsule
What are the GALTs?
Tonsils, adenoids, appendix, Peyer’s patches
What are the primary antigen presenting cells?
Dendritic cells
How does innate immunity function?
Recognition of pathogen-associated molecular patterns (PAMPs) which trigger macrophages to phagocytose the microbe
How does adaptive immunity function?
Antigens specific to the pathogen are identified and bound by B-lymphocytes which causes maturation and antibody production. Antibodies bind to the antigens and enable macrophages to identify foreign molecules and engulf them
How does the complement system function in innate immunity?
Opsonisation Lysis of pathogens Chemotaxis Inflammation Cell activation
How does the complement system function in adaptive immunity?
Augments the antibody response
Promotes T-cell response
Elimination of self-reactive B-cells
Enhancement of immunological memory
How does the complement system function in the disposal system?
Clearance of immune complexes and apoptotic cells
How does the complement system indicate infection?
Increased [C-proteins] in blood tests
Define Chemotaxis
Movement of an organism or cell towards a chemical stimulus
Define Extravasation and diapedesis
Extravasation - Forcing blood or lymph out of a vessel into surrounding tissue
Diapedesis - Neutrophils crossing between tissue and blood through the endothelium
What are the 3 branches of the complement system?
Classical pathway - Antibody binding
Lectin pathway - Mannose-binding lectin pathway
Alternative pathway - Pathogen surfaces
Which proteolytic enzymes are activated in the classical pathway?
C1, C2 and C4.
C4 causes the cleavage of C3
Which proteolytic enzymes are activated in the mannose-binding lectin pathway?
MLB, MASP, C2 and C4.
C4 causes the cleavage of C3
Which proteolytic enzymes are activated in the alternative pathway?
B and D.
D causes the cleavage of C3
What happens once C3 is cleaved?
Coating of microbes leading to phagocytosis
Recruitment of inflammatory cells
Activation of C5, C6, C7, C8 and C9 leading to cell lysis via formation of the membrane attack complex
What are the bodily physical defences of diseases?
Physical barriers - Skin, Mucous membranes, endothelial cells
Mechanical defences - Skin shedding, Mucouciliary escalator, Excretions, blinking
Microbiome
What are the bodily chemical defences?
Enzymes + chemicals in bodily fluids Antimicrobial peptides GI tract digestive enzymes Plasma protein mediators Cytokines Inflammation-eliciting mediators
What are the bodily cellular defences?
Granulocytes
Lymphocytes
What are the main macrophage receptors expressed on its cell surface?
Mannose receptor Lipopolysaccharide receptor CD11b/CD18 receptor Scavenger receptor Glucan receptor
What do toll-like receptors (TLRs) do?
Recognise a vast array of PAMPs
What are the types of antibody and how do they appear in the body?
IgA - Dimer with J-chain linker IgD - monomer IgE - monomer IgG - monomer IgM - Pentamer
What are the features of IgG?
Most common antibody
Found both intra and extra-vascularly
Facilitate phagocytosis of pathogens
Transferred from mother to foetus
What are the features of IgA?
2nd most abundant antibody
Intravascular localisation
Present in breast milk, tears and saliva
What are the features of IgM?
Activates the complement cascade
Is teh first antibody produced upon pathogen identification
What are the features of IgD?
Function on lymphocyte surfaces
What are the features of IgE?
Present on basophils and mast cell surfaces
Secreted in allergy response
How is antibody variability achieved?
VDJ recombination
What are the 2 types of T-cell and their functions?
T helper cell - stimulates B-cells to produce antibodies and induce phagocytosis by macrophages
T killer cells - to kill infected cells
How to T-cells become activated?
They come into contact with an antigen-presenting cell and present peptide fragments (10-20AA) on their cell surface
Which receptor is present on each T-cell?
CD4+ on T helper cells
CD8+ on T killer cells
Which major histocompatibility complex (MHC) binds which T-cell?
Class 1 MHCs bind to CD8+ T-killer cells
Class 2 MHCs bind to CD4+ T-helper cells
Where are MHC class 1 proteins found?
On almost every nucleated cell surface
Where are MHC class 2 proteins found?
Antigen presenting cells (B-cells, dendritic cells)
What happens when the CD4+ receptor is bound?
Cytokines are reeased which stimulates T-killer cell activation
What are the 2 subtypes of T-helper cell and what do they secrete?
Th1 - gamma-interferon, IL-2
Th2 - IL-4, IL-5
What do T-killer cells secrete?
IL-2 and gamma-interferon
What are the other t-cell subtypes and their functions?
Suppressor T-cells - suppress the immune system function
Natural killer T-cells - Immunosurveillance cytotoxic cells
gamma-delta-T-cells - Embryonic T-cell population
