Intro to Immunology Flashcards
What is a cytokine storm?
occurs when the immune system responds too aggressively to an infection
- elevated levels of circulating cytokines and immune cell hyperactivation
= causes a positive feedback loop
releases pro inflammatory cytokines
- TNF-alpha, IL-1, Natural Killer cells and IFN-gamma
What are auxiliary cells? What is their function?
cells which escalate inflammation and immunity
- attract leukocytes
- cause the release of inflammatory mediators (cytokines)
antibodies
mast cells
platelets
cytokines
e.g. TNF-alpha
- activate cells and surroundings the most during an inflammatory stimulus
How do neutrophils work?
are phagocytic cells
- die via a respiratory burst following phagocytosis
= use all their glycogen for this process
contain granules (lysosomes) that kill pathogens
What are the innate immune responses?
skin
- block the entry of pathogens and provide a hostile environment for growth
mucus
- traps microbes
mucous secretions
- saliva, tears and cilia = washing actions and bar microbe entry
stomach acid
- destroys microbes
lysozymes
- digest the cell wall of bacteria
tissue fluids
- contain microbial fluids
What are hematopoetic cells? What is their function?
are multipotent cells found in the bone marrow that develop into all types of blood cells
- erythrocytes, leukocytes and platelets
What are phagocytes? What are the different types? Which can communicate with the adaptive system?
a type of cell within the body capable of engulfing and absorbing bacteria and other small cells and particles
- neutrophils, basophils, eosinophils, natural killer cells, B cells, monocytes, dendritic cells, macrophages
monocytes, macrophages and dendritic cells can communicate with the adaptive system
- neutrophils cannot as they die via respiratory burst after phagocytosis
How are microbes recognised by cells of the immune system?
pathogen associated molecular patterns (PAMP)
- molecules on the microbial surface are recognised by pattern recognition receptors (PRR)
PAMP - bacterial carbohydrates, peptides (sugars or lipids)
PRR - toll like receptors (are on ALL phagocytic cells), carbohydrate receptors (lectin), scavenger receptor
opsonisation
- use of opsonins to tag foreign pathogens for elimination via phagocytosis
What is the mechanism of phagocytosis?
microbe binds to phagocyte receptors (PRR) via pathogen associated molecular pattern (PAMP)
phagocyte membrane encircles/zips up the pathogen and pinches off to to form a phagosome (intracellular vesicle)
phagosome fuses with lysosomes forming phagolysosome
- contains degradative enzymes
= reactive oxygen species (phagocyte oxidase), inducible nitric oxide synthase and protease
What are macrophages? What is their functions?
macrophages are phagocytic cells
- formed from monocytes (mononuclear cells)
are mostly associated with chronic inflammation and are tissue associated
phagocytose bacteria by extending pseudopodia and ‘lassoing’ bacteria
What are the main types of leukocytes?
What is leukocytosis, leukaemia and leukopenia?
types of leukocytes
- granulocytes = neutrophils, eosinophils, basophils (are ALL phagocytic)
- agranulocytes = monocytes, lymphocytes (B and T cells)
leukocytosis - elevated levels of leukocytes
leukaemia - cancer of leukocytes, increased number of immature or abnormal leukocytes
leukopenia - reduced levels of leukocytes
What is the function of basophils?
secrete
- histamine = vasodilator
- heparin = anticoagulant
- eosinophil chemotactic factors
generate
- leukotriene = bronchoconstrictor
What is the function of eosinophils?
- phagocytosis of antigen-antibody complexes, lessen severity of allergic reactions
- release enzymes to weaken or destroy parasites
release
- leukotrienes, inflammatory cytokines (IL-5, IL-13, IL-8), inflammatory proteins (EMBP, ECP)
What are dendritic cells?
antigen presenting cells (APC)
- initiate adaptive immune response
- are present in tissues that are in contact with external environment (dermis), they sample their environment and act as sentinels (langerhan cells do this and develop in to dendritic cells)
dendritic cells ingest the microbe and travel towards the lymph node where they present the antigen to T cells via their MHC II
Why do lymph nodes swell during infection?
Where are T cells educated?
Where does communication between the innate and adaptive system predominately happen?
lymph nodes swell during infection due to adaptive cells dividing an multiplying
T cells are educated in the thymus
ommunication between the innate and adaptive system predominately happens in the lymph
What is opsonisation?
tagging of a pathogen to make it more palatable for phagocytes
- coated with antibodies or complement factors
without opsonins, the negatively charged pathogens and phagocytes repel each other
