Lecture 2: cells of the innate immune system Flashcards
Pattern recognition receptors do what
Activation of the innate immune system occurs when molecules located on pathogens or damaged cells bind to pattern recognition receptors(PRRs) on phagocytic
There are hundreds of different types of PRRs
PRRs are found on
Many types of host defense cells but particularly on sentinel (look out) cells
Macrophages, dendritic cells, mast cells
Also found on neutrophils
Some circulate within the bloodstream
PRRs recognize what
Basic components common to pathogens
Essential components- widely distributed
Examples
Endotoxin of gram-negative bacteria
Viral RNA
Molecules released from damaged tissue e.g. heme
These molecules are not present in normal animal cells
What do PRRs do when activated
Stimulate inflammation and/or anti-parasitic activity
Also help with adaptive immunity
Sentinel cells are
Found in tissue at potential entry points
Activate immunity
Attract additional mobile defenders when needed
Tissue sentinel cells are
Macrophage
Dendritic cell/dendritic macrophage
Mast cell
Mobile cell in the innate immune system
Mobile cells can be sentinel, phagocytic or NK killer lymphocytes
Monocytes are found in
Blood
Why are they called monocytes
Undivided nucleus
Pleomorphic shape
Monocytes are what receptor type
Pattern recognition receptors
Antibody receptors
Functions of monocytes
Phagocytic
Remove dying neutrophils and tissue
Sentinel cells
Release mediators (cytokines) that stimulate innate and adaptive immune response
Migrate into tissues and become
Macrophages and dendritic cells
Macrophages are
Many are derived from blood monocytes
The most important type of sentinel cell
Dendritic cells are derived from
Derived from monocytes or lymphoid
Macrophages are found in
Macrophages stay in tissue
Recognize and react to bacteria, viruses, neutrophils, dead and damaged tissue
Stimulate innate and acquired immunity
What type of cells are macrophages and dendritic cells
Both are sentinel cells, phagocytic cells, and found in tissues
Where do dendritic cells move to
Dendritic cells move to lymph nodes after phagocytosing foreign material and stimulate adaptive immunity
Antigen presenting cells
Phagocytosis is
process by which certain living cells called phagocytes ingest or engulf other cells or particles.
Steps of phagocytosis
Step 1: Activation of the Phagocyte.
Step 2: Chemotaxis of Phagocytes (for wandering macrophages, neutrophils, and eosinophils)
Step 3: Attachment of the Phagocyte to the Microbe or Cell.
Step 4: Ingestion of the Microbe or Cell by the Phagocyte
Basophils are
White blood cell found in circulation
Basophilic (blue) staining granules
Mast cells are found in
Found in tissue
Often together with eosinophils
Mast cells look like
Similar in structure to basophils
Mast cells and basophils have common bone marrow precursors
Some mast cells arise from bone marrow and mature in the tissues
Other mast cells differentiate from blood and basophils
Function of basophils and mast cells
Sentinel cells- located near epithelial and endothelial surfaces
Degranulate and release histamine and heparin
Stimulate increased blood flow in early inflammation
With normal inflammation, release of inflammatory mediators is slow
Dominant cell in allergies and anaphylaxis
Stimulate complete degranulation
Basophils and mast cells are activated by
Activated by binding surfaces
PRRs
IgE
IgE is an antibody that binds strongly to basophils and mast cells
IgE activates the basophils or mast cell when it binds to antigen
An example of co-operation between the innate and adaptive system
Insect and animal venoms, bacteria, viruses
Neutrophils are
Granulocytic cells
They contain antibacterial granules
Also called
PMNs (polymorphonuclear neutrophils)
Because their nucleus is deeply divided
Immature neutrophils are called band cells
The nucleus is not yet lobulated
Properties of neutrophils
One of two major WBCs (40-75%) found in circulation (in the blood)
Short life span (days)
Highly mobile
Most are found in blood
Rapidly migrate to sites of inflammation
Neutrophils receptor types
Pattern recognition receptors for bacterial antigens
These recognize antigens common to groups of microbes or damaged tissue, ex. Endotoxin
Antigen- a substance that will initiate an immune response
Antibody receptors
Recognize IgG antibodies that have bound to an antigen
Antibody- a protein that binds to a specific antigen
Complement receptors
Complement is a group of blood proteins that are activated by pathogens
Neutrophils functions
destroy invading bacteria
Phagocytose bacteria and other small foreign particles
Destroy ingested material using
Enzymes e.g. lysozyme
Generating peroxides
Eosinophils are and contain
Lobed nucleus with orange-red granules
Attracted by chemicals released from mast cells and pathogens
Granules contain:
Proteins which destroy nearby tissue
Peroxides
Enzymes including RNAse
NK lymphocytes are
Mononuclear
Circulate in blood and tissues
Check cells for stress molecules and antigen presentation
Kill virus infected cells and tumour cells
Apoptosis- programmed cell death
Lysing the cell
These are the first responders to viral infections and tumours
