4. Immune system
Immune system – records microbial entry
Main parts are
WBC
Antibodies
Lymphatic system
Thymus, Bone marrow, Spleen
5. Immune system – Main
Characters
White Blood Cells
Bone marrow
Soldiers of the body
Constant Patrol
Antibodies
Microbes/Toxins
Antigens
Mark microbes / toxin as foreign.
6. Immune system – Main characters
Lymphatic system
Network of delicate tubes
Manage fluid level
Lymph nodes & lymph vessels
Lymphocytes
Thymes
Bone marrow
Spleen
7. Immune system and Microbial
Infection
First Line of
Defense
First Line of
Defense
Second Line
of Defense
Third Line of
Defense
01 03
02
8. About the Disease
Mars is a cold
place. The
planet is full
of iron oxide
dust
Mars
Is a gas giant
and the
biggest
planet in the
Solar
Jupiter
It’s a gas giant,
composed
mostly of
hydrogen
and helium
Saturn
9.
10.
11.
12.
13. About the Disease
Mars is a cold
place. The
planet is full
of iron oxide
dust
Mars
Is a gas giant
and the
biggest
planet in the
Solar
Jupiter
It’s a gas giant,
composed
mostly of
hydrogen
and helium
Saturn
Every day we’re exposed to millions of microscopic germs – bacteria, viruses, fungi, parasites. Our immune system protects us from them so that we don’t get sick.
But sometimes a germ (or pathogen) is able to get into our system – through a cut, from breathing in droplets from someone’s cough, or if our immune system has become weakened.
When this happens, our body launches an attack
Our immune system is essential for our survival. Without an immune system, our bodies would be open to attack from bacteria, viruses, parasites, and more. It is our immune system that keeps us healthy as we drift through a sea of pathogens.
Crucially, it can distinguish our tissue from foreign tissue — self from non-self. Dead and faulty cells are also recognized and cleared away by the immune system.
The immune system keeps a record of every microbe it has ever defeated, in types of white blood cells (B- and T-lymphocytes) known as memory cells. This means it can recognize and destroy the microbe quickly if it enters the body again, before it can multiply and make you feel sick.
Some infections, like the flu and the common cold, have to be fought many times because so many different viruses or strains of the same type of virus can cause these illnesses. Catching a cold or flu from one virus does not give you immunity against the others.
If the immune system encounters a pathogen, for instance, a bacterium, virus, or parasite, it mounts a so-called immune response. Later, we will explain how this works, but first, we will introduce some of the main characters in the immune system.
White blood cells are the key players in your immune system. They are made in your bone marrow and are part of the lymphatic system.
White blood cells move through blood and tissue throughout your body, looking for foreign invaders (microbes) such as bacteria, viruses, parasites and fungi. When they find them, they launch an immune attack.
White blood cells include lymphocytes (such as B-cells, T-cells and natural killer cells), and many other types of immune cells.
A white blood cell (yellow), attacking anthrax bacteria (orange).
Antibodies
Antibodies help the body to fight microbes or the toxins (poisons) they produce. They do this by recognizing substances called antigens on the surface of the microbe, or in the chemicals they produce, which mark the microbe or toxin as being foreign. The antibodies then mark these antigens for destruction. There are many cells, proteins and chemicals involved in this attack.
The lymphatic system is a network of delicate tubes throughout the body. The main roles of the lymphatic system are to:
manage the fluid levels in the body
react to bacteria
deal with cell products that otherwise would result in disease or disorders
absorb some of the fats in our diet from the intestine.
The lymphatic system is made up of:
lymph nodes (also called lymph glands) -- which trap microbes
lymph vessels -- tubes that carry lymph, the colourless fluid that bathes your body's tissues and contains infection-fighting white blood cells
lymphocytes).
Lymphocytes help the body to remember previous invaders and recognize them if they come back to attack again.
The spleen is a blood-filtering organ that removes microbes and destroys old or damaged red blood cells. It sits in the upper left of the abdomen.
Thymus — a gland between the lungs and just below the neck. The thymus produces the white blood cells called T-lymphocytes.
Bone marrow — found in the center of the bones, it also produces red blood cells.
Bone marrow is the spongy tissue found inside your bones. It produces the red blood cells our bodies need to carry oxygen, the white blood cells we use to fight infection, and the platelets we need to help our blood clot.
Lymphocytes begin their life in bone marrow. Some stay in the marrow and develop into B lymphocytes (B cells),
Our immune system protects us from them so that we don’t get sick.
But sometimes a germ (or pathogen) is able to get into our system – through a cut, from breathing in droplets from someone’s cough, or if our immune system has become weakened.
When this happens, our body launches an attack.
It starts with the white blood cells (or leukocytes). They’re our germ fighting cells. They patrol the body looking for foreign bodies like viruses.
Every day we’re exposed to millions of microscopic germs – bacteria, viruses, fungi, parasites.
But sometimes a germ (or pathogen) is able to get into our system – through a cut, from breathing in droplets from someone’s cough, or if our immune system has become weakened.
The innate response begins immediately and can identify and destroy invaders quickly.
This innate immunity includes the external barriers of our body
The first line of defense against pathogens — such as the skin and mucous membranes of the throat and gut.
This response is more general and non-specific. If the pathogen manages to dodge the innate immune system, adaptive or acquired immunity kicks in.
skin - a waterproof barrier that secretes oil with bacteria-killing properties
other defenses - body fluids like skin oil, saliva and tears contain anti-bacterial enzymes that help reduce the risk of infection. The constant flushing of the urinary tract and the bowel also helps.
lungs - mucous in the lungs (phlegm) traps foreign particles, and small hairs (cilia) wave the mucous upwards so it can be coughed out
digestive tract - the mucous lining contains antibodies, and the acid in the stomach can kill most microbes
two innate immune responses are triggered, phagocytosis and inflammatory responses.
They all play important roles in the immune system.
These cells surround and absorb pathogens and break them down, effectively eating them. There are several types, including:
Mast cells — they have many jobs, including helping to heal wounds and defend against pathogens.
Neutrophils — these are the most common type of phagocyte and tend to attack bacteria.
Monocytes — these are the largest type and have several roles.
Macrophages — these patrol for pathogens and also remove dead and dying cells.
Phagocytes are hungry little buggers that eat pathogens for breakfast.
They do this by surrounding the cell and absorbing it.
When they do this they receive information from the proteins on the surface of the pathogen.
These proteins are called antigens (or antibody generators). Phagocytes then send this info to the lymphocytes.
The complement system is another vital component of the immune system. It works with the innate and adaptive responses. It is a cascade of proteins that alter or fragment later proteins, in specific sequences.
The cascade triggers many actions including recruiting inflammatory cells, attracting phagocytes to the area and marking pathogens for phagocytosis, damaging the plasma membrane of a pathogen leading to its death and removing neutralized antigen-antibody complexes from the body.
The signaling molecules that are used by cells of the immune system to communicate with each other are known as cytokines
An antigen is a bacterium, fungus, virus, toxin, or foreign body.
But it can also be one of our own cells that is faulty or dead.
Initially, a range of cell types works together to recognize the antigen as an invader.
Helper T cells (Th cells) — they coordinate the immune response. Some communicate with other cells, and some stimulate B cells to produce more antibodies. Others attract more T cells or cell-eating phagocytes.
Killer T cells (cytotoxic T lymphocytes) — as the name suggests, these T cells attack other cells. They are particularly useful for fighting viruses. They work by recognizing small parts of the virus on the outside of infected cells and destroy the infected cells.