Innate immunity Flashcards
What is an antigen?
Any molecule that is capable of inducing an immune response
Describe the innate immune system in terms of response speed, recognition of threats, antigen presentation, clonal selection, and immunological memory.
Immediate response
Recognises certain threats
No antigen presentation
No clonal selection
No immunological memory
Describe the adaptive immune system in terms of response speed, recognition of threats, antigen presentation, clonal selection, and immunological memory.
Delayed response
Recognises all threats
Antigen presentation
Clonal selection
Immunological memory
List the 3 broad components of the innate immune system.
Physical barriers
Leukocytes
Plasma proteins
Name a glycoprotein found in the mucus of interior epithelial surfaces and how it helps prevent disease.
Mucins – which prevents pathogens from adhering and facilitates their clearance by cilia
Name a peptide found in mucus and how it helps prevent disease.
Defensins – which kill or inhibit the growth of pathogens
What are the 2 common progenitor cell types that come from the multipotent haemopoietic progenitor?
Common lymphoid progenitor Common myeloid progenitor
Common lymphoid progenitor cells give rise primarily to cells of which branch of the immune system?
Adaptive immune system
Common myeloid progenitor cells give rise primarily to cells of which branch of the immune system?
Innate immune system
Which cells that originate from the common lymphoid progenitor are actually part of the innate immune system?
Natural killer cells
Which 4 cells comprise the granulocytes?
Neutrophils
Eosinophils
Basophils
Mast cells
Which 2 cell types do monocytes differentiate into once they enter tissues?
Macrophages
Dendritic cells
What do megakaryocytes produce?
Platelets
What is the lifespan of erythrocytes in circulation?
4 months
Which 3 cell types of the innate immune system are capable of phagocytosis?
Macrophages
Dendritic cells
Neutrophils
How do macrophages and dendritic cells also link to the adaptive immune response?
They process and present antigens to T-cells for the adaptive immune response
Describe the process of phagocytosis.
Chemotaxis and adherence of microbe to phagocyte.
Ingestion of microbe by phagocyte.
Formation of a phagosome.
Fusion of the phagosome with a lysosome to form a phagolysosome.
Digestion of ingested microbe by enzymes.
Formation of residual body containing indigestible material.
Discharge of waste materials.
Other than degradative enzymes, how else does phagocytosis kill microbes?
What is this process known as?
Oxidative burst – in which cells produce reactive oxygen species (ROS) damage microbial proteins, lipids, and DNA
Where in the body do antigen-presenting dendritic cells come into contact with T-cells to activate the adaptive immune response?
Lymph nodes
Eosinophils are most important in defence against what?
Parasites
Describe the shape of a neutrophil nucleus.
Multi-lobed (3 or more)
Describe the colour staining of eosinophils and the shape of their nuclei.
Pink
Bi-lobed
NK cells kill which 2 types of cell?
Virally infected cells
Malignant cells
Describe how NK cells kill cells.
Create holes in cell membranes
Inject enzymes which trigger apoptosis
What does PAMPs and PRRs stand for?
Pathogen-associated molecular patterns
Pattern recognition receptors
What are PAMPs?
Molecular structures found on pathogens that are not normally present in the host
What are PRRs?
Receptors found on the surface of immune cells which recognize and bind to PAMPs
What is the prototypical example of a PAMP?
Lipopolysaccharides found in the outer membrane of gram-negative bacteria
List 2 acute phase proteins.
C-reactive protein (CRP)
Complement factors
Which process does CRP induce which helps remove pathogens?
Opsonization – CRP binds to pathogens, labelling them for phagocytosis
Which branch of the immune system is the complement system part of?
Part of the innate immune system, but with links to the adaptive immune system
What are the 3 pathways of the complement system?
Classical
Alternative
Lectin
What is the key step in the complement system, where all the prior reactions converge?
Cleavage of inactive C3 protein into active C3a and C3b fragments
What is the effect of active C3a?
Inflammation
What is the effect of active C3b?
Opsonization + phagocytosis
The end goal of the complement system is to form what?
Membrane attack complexes (MAC)
Describe the classical complement pathway.
The classical pathway is part of the adaptive immune response.
The binding of an antibody (IgM or IgG) to its antigen activates the first protein in the complement system, C1, which initiates a protein cleavage cascade
Describe the alternative complement pathway.
Direct interaction and binding of C3 with pathogens promotes C3 cleavage
Describe the lectin complement pathway.
Mannose-binding lectin binds to mannose on the surface of pathogens and initiates a protein cleavage cascade
Which 2 cells of the innate immune system carry out antigen presentation?
Macrophages
Dendritic cells
List the 3 main ROS.
Superoxide anion
Hydrogen peroxide
Hydroxyl radical
What feature do macrophages have which helps them move?
Pseudopodia
Which molecule is released by NK cells to create holes in the cell membrane?
Perforin
Which enzymes are injected into cells by NK cells to trigger apoptosis?
Granzymes
What is the function of chemokines?
Induce chemotaxis
What is the function of interferons?
Produced by virally-infected cells to warn neighbouring cells and help them resist infection
