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
Relatively poor regulation of response in the innate immune system can compromise the system’s ability to distinguish between what? What does this increase the risk of?
Distinguish between harmful and harmless agents, increasing the risk of self-targeted damage and autoimmunity
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
Give the 4 main cell types of the common myeloid progenitor cells.
Granulocytes
Monocytes
Megakaryocytes
Erythrocytes
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 such as macrophages and neutrophils produce reactive oxygen species (ROS) which are unstable molecules such as hydrogen peroxide and superoxide anions that 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 neutrophil nuclei.
Multi-lobed
Describe the colour staining of eosinophils and the shape of their nuclei.
Pink
Bi-lobed
What do NK cells kill?
Virally infected or malignant cells
Describe how NK cells kill cells.
They release cytotoxic granules containing perforin which forms pores in the target cell’s membrane, creating entry points for granzymes - 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 PAMPs?
Lipopolysaccharides found in the outer membrane of gram-negative bacteria
What are cytokines? Give 2 examples.
Small protein signalling molecules
Interleukins + interferons
What are acute phase proteins? Give 2 examples.
Humoral factors that are up-regulated or down-regulated in response to inflammation
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 and how does this help destroy pathogens?
Inflammation – release of inflammatory mediators attracts immune cells to the site of infection
What is the effect of active C3b?
Opsonization
What does the complement cascade form which helps to destroy pathogens?
Membrane attack complexes (MAC) which insert themselves into the membrane of pathogens, creating pores that cause the pathogen to burst (lysis)
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
