How the immune system works

How the immune system works

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.

This vast network of cells and tissues is constantly on the lookout for invaders, and once an enemy is spotted, a complex attack is mounted.

The immune system is spread throughout the body and involves many types of cells, organs, proteins, and tissues. 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.

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

A white blood cell (yellow), attacking anthrax bacteria (orange). The white line at the bottom is 5 micrometers long.

Image credit: Volker Brinkmann

White blood cells are also called leukocytes. They circulate in the body in blood vessels and the lymphatic vessels that parallel the veins and arteries.

White blood cells are on constant patrol and looking for pathogens. When they find a target, they begin to multiply and send signals out to other cell types to do the same.

Our white blood cells are stored in different places in the body, which are referred to as lymphoid organs. These include the following:

Thymus — a gland between the lungs and just below the neck.

Spleen — an organ that filters the blood. It sits in the upper left of the abdomen.

Bone marrow — found in the center of the bones, it also produces red blood cells.

Lymph nodes —small glands positioned throughout the body, linked by lymphatic vessels.

There are two main types of leukocyte:

1. Phagocytes

These cells surround and absorb pathogens and break them down, effectively eating them. There are several types, including:

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.

Mast cells — they have many jobs, including helping to heal wounds and defend against pathogens.

2. Lymphocytes

Lymphocytes help the body to remember previous invaders and recognize them if they come back to attack again.

Lymphocytes begin their life in bone marrow. Some stay in the marrow and develop into B lymphocytes (B cells), others head to the thymus and become T lymphocytes (T cells). These two cell types have different roles:

B lymphocytes — they produce antibodies and help alert the T lymphocytes.

T lymphocytes — they destroy compromised cells in the body and help alert other leukocytes.

 

BOOST YOUR IMMUNE SYSTEM

David

What Is your Immune system?

What Is Your Immune System?

You’ve heard of your immune system. But how much do you know about it?

There’s a good reason to find out. When you understand everything that it does for you, and how everyday things affect it, you can help it keep you well.
 

1. It Looks Out for You

Your immune system works to root out germs and other invaders that have no business in your body.

For example, if you inhale a cold virus through your nose, your immune system targets that virus and either stops it in its tracks or primes you to recover. It takes time to get over an infection, and sometimes you need medicine to help, but the immune system is the cornerstone of prevention and recovery.

2. It Likes It When You Relax

Do your best to tame your stress. When you’re wound up, your immune system doesn’t work as well as it does when you’re confident and mellow about your challenges. That may make you more likely to get sick.

3. It’s Got Agents Standing By.

Other than your nervous system, your immune system is the most complex system in your body. It’s made up of tissues, cells, and organs, including:

4. It Learns From Your Past

You’re born with a certain level of protection, or “immunity.” But it can get better.

Think of a baby or young child who comes down with colds, earaches, or other everyday illnesses often and babies who are breast feed continue to get antibodies from their mother while they are making their own.. Their immune system is creating a "bank"of antibodies as they are exposed to illnesses for the first time, enabling them to fight off future invaders.

Vaccines work in much the same way. They turn on your immune system by introducing your body to a tiny amount of a virus (usually a killed or weakened one). Your body makes antibodies in response that protects against threats like measles, whooping cough, flu, or meningitis.Then, when you come in contact with that virus in your everyday life, your immune system is already primed to kick in so that you don’t get sick.

5. It Can Change Over Time

Your immune system can become less effective as you get older. That can make you more likely to get sick or get infections. You are also more susceptable to infections as you age or if you have a weakened immune system.

6. Medical Conditions that Weaken your immune system

Conditions which can weaken you immune system include:

autoimmune diseases

cancer

steroids

chemotherapy

7. You Can Help It Out

The classic things that keep your heart, brain, bones, and the rest of you well are also good for your immune system:

Eat nutritious foods.

Stay active.

Work to keep your weight healthy.

Don’t smoke.

If you drink alcohol, keep it moderate (no more than one drink a day if you’re a woman, and two drinks daily if you’re a man)

 

Boost your Immune System

David

The Daily Telegraph has report Vitamin D immune system boost?

The Daily Telegraph has report Vitamin D immune system boost?
The Daily Telegraph has reported that “vitamin D 'triggers and arms' the immune system”. It said that researchers believe that vitamin D plays a key role in boosting the immune system.

The study looked at human T cells in the laboratory, and found that vitamin D was part of a complex process in which T cells become 'primed' and help to fight infection. While these findings suggest that people with vitamin D deficiency are more susceptible to infection or that vitamin D supplements might boost immunity, such theories need to be tested further before drawing any firm conclusions.

It is important to have enough vitamin D to maintain a healthy body. Vitamin D forms in our skin in response to sunlight. However, care should be taken to avoid burning or over-exposure. Vitamin D is also found in foods such as oily fish, eggs, fortified margarines, some breakfast cereals and vitamin supplements.

Where did the story come from?

Dr Marina Rode von Essen and colleagues from the University of Copenhagen and Bispebjerg Hospital in Denmark carried out this research. The study was funded by the Danish Medical Research Council, the Lundbeck Foundation, the Novo Nordisk Foundation, the King Christian the 10th Foundation and the A.P. Møller Foundation for the Advancement of Medical Sciences. Some of the chemicals used in the study were provided by the manufacturer Bayer Schering Pharma AG. The paper was published in the peer-reviewed scientific journal Nature Immunology.

The study was reported in The Daily Telegraph, Daily Mail, and Metro . The newspapers give reasonable coverage of this complex research. Metro includes the study’s sensible warning that sunburn should be avoided.

What kind of research was this?

This laboratory research investigated what happens to human T cells when they respond to foreign molecules (called antigens). T cells are immune-system cells that recognise antigens (for example molecules on the surfaces of viruses) and kill infected cells. In particular, the researchers looked at the 'priming' of the T cells, a process by which T cells prepare to respond to antigens. When exposed to an antigen, primed T cells are able to multiply in number faster and produce more chemicals to help promote further immune response than naive T cells. They looked at the role of a protein called phospholipase C, which is involved in sending signals within cells. They also looked at how vitamin D and the vitamin D receptor are involved in this process.

This type of laboratory study helps researchers to unravel the complex events that occur in individual cells in the immune system. A better understanding of how the immune system works could suggest ways of boosting immune responses. In this case, if vitamin D was found to play a role in the immune system, this would suggest that people with vitamin D deficiency might be more susceptible to infection or that vitamin D supplements might boost immunity. Such theories would have to be tested in human research before any firm conclusions could be drawn.

 What did the research involve?

The researchers took 'naive' (unprimed by exposure to antigens) human T cells from freshly drawn blood and grew them in the laboratory. They grew some in solutions containing immune system molecules: conditions that 'primed' them for activation.

The characteristics and behaviour of the 'primed' T cells were then compared with the 'naive' T cells. This included the cells’ response to being 'restimulated' through re-exposure to the immune system molecules that originally primed their activation.

The researchers were especially interested in how much the cells produced a particular form of phospholipase C, called phospholipase C-γ1, and how this was linked to the presence of the vitamin D receptor. They also looked at what happened if they blocked the cells from responding to vitamin D. They carried out experiments to investigate how the cells switched on the production of the vitamin D receptor.

What were the basic results?

The researchers found that 'naive' T cells that had not been primed produced only a small amount of phospholipase C-γ1. However, following priming by exposure to the activator immune system molecules, the T cells began to produce far more phospholipase C-γ1. For this to occur, the T cells needed to be in the presence of vitamin D and the vitamin D receptor.

They also found that naive T cells did not produce the vitamin D receptors, and that these receptors were only produced when the T cells were primed.

How did the researchers interpret the results?

The researchers conclude that T cells produce vitamin D receptors when they are primed to respond to antigens. Vitamin D then acts via the receptor to stimulate production of phospholipase C-γ1. These changes are necessary for the T cells to be activated.

Conclusion

This research indicates that vitamin D is involved in the activation of the T cells of the immune system. It is important to note that this is a laboratory study, and it is useful in helping researchers to understand what happens in specific immune system cells when exposed to foreign entities such as bacteria or viruses. It does not tell us how variations in vitamin D levels might affect people’s susceptibility to infection, or what the ideal level of vitamin D is for supporting immune system responses to infection.

Other studies will no doubt look into these questions. However, as with other vitamins, it is clearly important to have sufficient vitamin D to maintain a healthy body. Vitamin D forms in our skin in response to sunlight, but care should still be taken to avoid burning or over-exposure. Vitamin D is also found in foods such as oily fish, eggs, fortified margarines, some breakfast cereals and vitamin supplements.

Analysis by Bazian

David