Lecture 2: cells of the innate immune system

Question 1

Pattern recognition receptors do what

Answer 1

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

Question 2

PRRs are found on

Answer 2

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

Question 3

PRRs recognize what

Answer 3

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

Question 4

What do PRRs do when activated

Answer 4

Stimulate inflammation and/or anti-parasitic activity
Also help with adaptive immunity

Question 5

Sentinel cells are

Answer 5

Found in tissue at potential entry points
Activate immunity
Attract additional mobile defenders when needed

Question 6

Tissue sentinel cells are

Answer 6

Macrophage
Dendritic cell/dendritic macrophage
Mast cell

Question 7

Mobile cell in the innate immune system

Answer 7

Mobile cells can be sentinel, phagocytic or NK killer lymphocytes

Question 8

Monocytes are found in

Answer 8

Blood

Question 9

Why are they called monocytes

Answer 9

Undivided nucleus
Pleomorphic shape

Question 10

Monocytes are what receptor type

Answer 10

Pattern recognition receptors
Antibody receptors

Question 11

Functions of monocytes

Answer 11

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

Question 12

Macrophages are

Answer 12

Many are derived from blood monocytes
The most important type of sentinel cell

Question 13

Dendritic cells are derived from

Answer 13

Derived from monocytes or lymphoid

Question 14

Macrophages are found in

Answer 14

Macrophages stay in tissue
Recognize and react to bacteria, viruses, neutrophils, dead and damaged tissue
Stimulate innate and acquired immunity

Question 15

What type of cells are macrophages and dendritic cells

Answer 15

Both are sentinel cells, phagocytic cells, and found in tissues

Question 16

Where do dendritic cells move to

Answer 16

Dendritic cells move to lymph nodes after phagocytosing foreign material and stimulate adaptive immunity
Antigen presenting cells

Question 17

Phagocytosis is

Answer 17

process by which certain living cells called phagocytes ingest or engulf other cells or particles.

Question 18

Steps of phagocytosis

Answer 18

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

Question 19

Basophils are

Answer 19

White blood cell found in circulation
Basophilic (blue) staining granules

Question 20

Mast cells are found in

Answer 20

Found in tissue
Often together with eosinophils

Question 21

Mast cells look like

Answer 21

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

Question 22

Function of basophils and mast cells

Answer 22

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

Question 23

Basophils and mast cells are activated by

Answer 23

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

Question 24

Neutrophils are

Answer 24

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

Question 25

Properties of neutrophils

Answer 25

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

Question 26

Neutrophils receptor types

Answer 26

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

Question 27

Neutrophils functions

Answer 27

destroy invading bacteria
Phagocytose bacteria and other small foreign particles
Destroy ingested material using
Enzymes e.g. lysozyme
Generating peroxides

Question 28

Eosinophils are and contain

Answer 28

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

Question 29

NK lymphocytes are

Answer 29

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