What is the immune system?
This network of tissues, cells, and organs first tries to keep out germs like bacteria, viruses, fungi, and parasites and then deals with them if they manage to get in. The immune system protects the body against disease or other potentially damaging foreign bodies. If it senses something in your body that could be bad for you, it triggers the release of special cells. These travel to where the trouble is, attack the intruder, and help get rid of it.
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.
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.
How Do Infections Spread?
Your body has to be able to stop invaders that come from a lot different places. Germs can come from contact -- touching skin, having sex, and breathing in drops from someone else's sneeze or cough, for example. They can travel through blood that comes from a shared needle or an insect bite. You can also get germs from contaminated food or water.
There are two main parts of the immune system:
The innate immune system, which you are born with.
The adaptive immune system, which you develop when your body is exposed to microbes or chemicals released by microbes. These two immune systems work together.
The innate immune system
We are all born with some level of immunity to invaders. Human immune systems, similarly to those of many animals, will attack foreign invaders from day one. 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.
The acquired immune system
This protect from pathogens develops as we go through life. As we are exposed to diseases or get vaccinated, we build up a library of antibodies to different pathogens. This is sometimes referred to as immunological memory because our immune system remembers previous enemies.
The acquired immune system, with help from the innate system, produces cells (antibodies) to protect your body from a specific invader. These antibodies are developed by cells called B lymphocytes after the body has been exposed to the invader. The antibodies stay in your child's body. It can take several days for antibodies to develop. But after the first exposure, the immune system will recognize the invader and defend against it. The acquired immune system changes throughout your child's life. Immunizations train your child's immune system to make antibodies to protect him or her from harmful diseases.
This type of immunity is “borrowed” from another source, but it does not last indefinitely. For instance, a baby receives antibodies from the mother through the placenta before birth and in breast milk following birth. This passive immunity protects the baby from some infections during the early years of their life.
The immune system can recognize millions of different antigens. And it can produce what it needs to eradicate nearly all of them. When it’s working properly, this elaborate defense system can keep health problems ranging from cancer to the common cold at bay.
White blood cells
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 vessel
There are two main types of leukocyte:
These cells surround and absorb pathogens and break them down, effectively eating them.
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:
1. B lymphocytes — they produce antibodies and help alert the T lymphocytes.
2. T lymphocytes — they destroy compromised cells in the body and help alert other leukocytes.
Everyone’s immune system is different but, as a general rule, it becomes stronger during adulthood as, by this time, we have been exposed to more pathogens and developed more immunity. That is why teens and adults tend to get sick less often than children. Once an antibody has been produced, a copy remains in the body so that if the same antigen appears again, it can be dealt with more quickly.
That is why with some diseases, such as chickenpox, you only get it once as the body has a chickenpox antibody stored, ready and waiting to destroy it next time it arrives. This is called immunity.
Signs You Have a Weakened Immune System
1. Your Stress Level is Sky-High
That’s because stress decreases the body’s lymphocytes, the white blood cells that help fight off infection. The lower your lymphocyte levels, the more you’re at risk for viruses like the common cold
2. You Always Have a Cold
It’s perfectly normal for adults to sneeze and sniffle through two or three colds each year. Most people bounce back in seven to 10 days. During that time, it takes the immune system three to four days to develop antibodies and fight off pesky germs But if you’re constantly catching colds – or have a cold that’s won’t run its course – that’s a clear sign your immune system is struggling to keep up.
3. You Have Lots of Tummy Troubles
If you have frequent diarrhea, gas or constipation, it could be a sign that your immune system is compromised. Research shows that nearly 70 percent of your immune system is located in your digestive tract. The beneficial bacteria and microorganisms that live there defend your gut from infection and support the immune system. Low amounts of these helpful gut bacteria can leave you at risk to viruses, chronic inflammation and even autoimmune disorders.
4.Your Wounds Are Slow to Heal
Your skin goes into damage control mode after you get a burn, cut or scrape. Your body works to protect the wound by sending nutrient-rich blood to the injury to help regenerate new skin.
This healing process depends on healthy immune cells. But if your immune system is sluggish, your skin can’t regenerate. Instead, your wounds linger and have a hard time healing.
5.Have Frequent Infections
If you seem battle frequent infections, your immune system might be sending you red flags.
The American Academy of Allergy Asthma & Immunology reports that signs of a possible immune deficiency in adults include: Having more than four ear infections in one year
Developing pneumonia twice during a one-year period Suffering from chronic sinusitis or more than three episodes of bacterial sinusitis in a year Needing more than two courses of antibiotics a year
6. You Feel Tired All the Time
You know that burning the candle at both ends is bound to leave you feeling sluggish. But if you’re getting enough sleep and still suffering from exhaustion, it’s worth considering if your immune system is trying to tell you something.
When your immune system struggles, so does your energy level. That's because your body is trying to conserve energy to fuel your immune system so it can fight off germs.
Ways to Boost Your Immune System
There’s no single pill or supplement you can take to boost your immune system. Instead, adopting these healthy living habits can help improve your immunity for a lifetime.
If the above warning signs are familiar, you need to give your immune system some extra attention. A few lifestyle changes and new habits can naturally keep your immune system strong and healthy: