Lecture 31 - innate immunity I

Question 1

Innate immunity

Answer 1

Not very specific, broadly acting, fast however it can tell a virus apart from a bacterium

Recognise broad molecular patterns (PAMPs)

Question 2

Immune cells in the blood

Answer 2

Blood is composed of plasma (55% - proteins, solutes and water) and cells (45% - platelets, RBCs and WBCs)

Question 3

Formed elements

Answer 3

cells

Makes up 45% of blood and includes platelets, white blood cells (leukocytes) and red blood cells

Question 4

Leukocytes

Answer 4

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.

Question 5

Plasma

Answer 5

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

Question 6

Bone marrow

Answer 6

Bone marrow stem cells are the source of all blood cells via hematopoiesis (formation of blood cells)

Question 7

Haemopoiesis

Answer 7

the production of blood cells and platelets, which occurs in the bone marrow

Question 8

What are the 3 blood cell lineages?

Answer 8

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

Question 9

Erythroid

Answer 9

Erythroid is red blood cells (erythrocytes)

Question 10

Myeloid

Answer 10

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)

Question 11

Lymphoid

Answer 11

Lymphoid is B and T lymphocytes (adaptive immune cells)

Question 12

Granulocytes

Answer 12

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

Question 13

Neutrophils

Answer 13

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.

Question 14

Mast cells

Answer 14

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

Question 15

Monocytes and macrophages connection

Answer 15

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

Question 16

Phagocytosis

Answer 16

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.

Question 17

Macrophages

Answer 17

Macrophages become resident (sessile) or move through tissues (migratory)

Major phagocytic cell in the immune system

Question 18

Functions of macrophages

Answer 18

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)

Question 19

Dendritic cells

Answer 19

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

Question 20

How do cells of the immune system move around the body?

Answer 20

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)

Question 21

How do innate cells recognise pathogens?

Answer 21

Pathogen-associated molecular patterns (PAMPS)

Question 22

PAMPs

Answer 22

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

Question 23

Virus PAMPs

Answer 23

Common building blocks of viruses - nucleic acids = ssRNA, dsRNA

Question 24

Virus main features

Answer 24

Envelope
Nucleocapsid
Nucleic acid

Question 25

Bacterium main features

Answer 25

Capsule 
Cell wall 
Cell membrane 
Nucleic acid 
Flagella

Question 26

Bacterium PAMPs

Answer 26

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)

Question 27

Toll like receptors

Answer 27

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)

Question 28

Toll like receptors vs pattern recognition receptors

Answer 28

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.

Question 29

Fever

Answer 29

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.

Question 30

Pyrogens

Answer 30

a substance, typically produced by a bacterium, which produces fever when introduced or released into the blood.