Lecture 31 - innate immunity I Flashcards
Innate immunity
Not very specific, broadly acting, fast however it can tell a virus apart from a bacterium
Recognise broad molecular patterns (PAMPs)
Immune cells in the blood
Blood is composed of plasma (55% - proteins, solutes and water) and cells (45% - platelets, RBCs and WBCs)
Formed elements
cells
Makes up 45% of blood and includes platelets, white blood cells (leukocytes) and red blood cells
Leukocytes
White blood cells are also called leukocytes
Immune cells that circulate our blood and patrol our body
Cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders.
Plasma
Makes up 55% of blood and it includes proteins (including antibodies (Y shaped molecules produced by B cells) and immunoglobulin (very specific and can bind to a particular pathogen and inactivate it)), other solutes and water
This is the liquid part of blood
Bone marrow
Bone marrow stem cells are the source of all blood cells via hematopoiesis (formation of blood cells)
Haemopoiesis
the production of blood cells and platelets, which occurs in the bone marrow
What are the 3 blood cell lineages?
Erythroid is red blood cells (erythrocytes)
Myeloid is granulocytes - lots of granules in these cells, monocytes - big nucleus, dendritic cells - critical cells for the communication to the adaptive immune cells, platelets (innate immune cells)
Lymphoid is B and T lymphocytes (adaptive immune cells)
All of these lineages are derived from hematopoietic stem cells in the bone marrow(these cells have the ability to differentiate into many different cells)
Myeloid cells and lymphoid cells are known as white blood cells
Erythroid
Erythroid is red blood cells (erythrocytes)
Myeloid
Myeloid is granulocytes - lots of granules in these cells, monocytes - big nucleus, dendritic cells - critical cells for the communication to the adaptive immune cells, platelets (innate immune cells)
Lymphoid
Lymphoid is B and T lymphocytes (adaptive immune cells)
Granulocytes
Granulocytes are a category of white blood cells in the innate immune system characterized by the presence of granules in their cytoplasm.
Granulocytes circulate in the blood and can move into tissue during inflammation
e.g. neutrophils
Neutrophils
75% of all leukocytes, highly phagcytic (eat and kill) - numbers in the blood increase during infection
Therefore high numbers in the blood indicate infection
Phagocytosis is central to the microbicidal function of neutrophils.
Mast cells
Mast cell line mucosal surfaces (not found in blood) (sites that are exposed to air)
Release granules that attract white blood cells to areas of tissue damage
Monocytes and macrophages connection
Monocytes present in blood…low phagocytosis …Leave blood and develop into macrophages in tissues e.g. spleen and liver ….now high phagocytosis
Monocyte is the precursor of a macrophage
Phagocytosis
Phagocytosis is a specific form of endocytosis by which cells internalise solid matter, including microbial pathogens. While most cells are capable of phagocytosis, it is the professional phagocytes of the immune system, including macrophages, neutrophils and. mmature dendritic cells, that truly excel in this process.
Macrophages
Macrophages become resident (sessile) or move through tissues (migratory)
Major phagocytic cell in the immune system
Functions of macrophages
3 important functions:
Phagocytosis (professional eaters) (eat foreign matter that comes into the body)
Release chemical messengers (not secreted in granules, instead slowly secreted to other cells)
Show information about pathogenic microbes to T cells (linking innate and adaptive immunity)
Dendritic cells
Found in low numbers in the blood and all tissues in contact with the environment (although there are low numbers everywhere they are very potent so they are very good at what they do)
These cells are phagocytic
Most important cell type to help trigger adaptive immune responses//Links the innate and adaptive immune response
Arms/spikes/dendrites allow these cells to have a very big surface area so they come into contact with lots of cells and lots of tissues
How do cells of the immune system move around the body?
Cells are carried in the blood and in the lymph
Cells can leave the blood to enter tissues
Lymph tissues collects into lymphatic vessels. These drain lymph fluid into the lymph nodes. (it is here where the innate cells can interact with the adaptive cells and start an adaptive immune response)
How do innate cells recognise pathogens?
Pathogen-associated molecular patterns (PAMPS)
PAMPs
Pathogen-associated molecular patterns (PAMPS) - feature/pattern in a certain group of bacteria or viruses that are common
Event though they look very different to the eye they do have a feature in common. Innate cells are able to recognise the difference between viruses and bacteria by the common building blocks shared by each group.
If these building block are detected then it is a signal that something is present that should not be there
Virus PAMPs
Common building blocks of viruses - nucleic acids = ssRNA, dsRNA
Virus main features
Envelope
Nucleocapsid
Nucleic acid
Bacterium main features
Capsule Cell wall Cell membrane Nucleic acid Flagella
Bacterium PAMPs
Common building blocks of bacteria -
Cell wall - lipopolysaccharide (LPS)/endotoxins, lipoteichoic acid
Flagella - flagellin
Nucleic acid - unmethylated CpG DNA (nucleic acid becomes revealed when the organism is broken down)
Toll like receptors
Protein receptors present on phagocytes that recognize conserved microbial structures, e.g. microbial cell wall components or microbial nucleic acids. TLR may be present on the plasma membrane (TLR4, TLR5) or inside the cell in vesicles (TLR3, TLR9) in the phagolysosome vesicle. They send cell signalling to regulate gene transcription (some genes are expressed more and some genes are inhibited more)
Recognise PAMPs (building blocks)
Toll like receptors vs pattern recognition receptors
toll like receptors and pattern recognition receptors are the same thing. TLRsare and example of a pattern recognition receptor and TLR is the proper biological term.
Fever
Pyrexia is another name for fever
Abnormally high temperature above 37 degrees.
There is resetting of thermostat at the hypothalamus
Pyrogens are released by the cells of the immune system - such as IL-1
Phagocytes produce the chemical messenger and pyrogen interleukin-1 (IL-1) after ingesting bacteria
As the phagocytic cells break down all of the pathogen, eventually less occurs as there is less pathogens therefore phagocytosis decreases which causes IL-1 to decrease which causes decrease in temperature
Could inhibit replication of bacteria or virus. Could increase immune cell function, increase gene expression/transcription in immune cells so that you get more of the molecules that are really important to produce.
Pyrogens
a substance, typically produced by a bacterium, which produces fever when introduced or released into the blood.
