Antibiotics were developed to kill or disable specific bacteria. That means that an antibiotic that works for a skin infection may not work to cure diarrhea caused by bacteria. Using antibiotics for viral infections or using the wrong antibiotic to treat a bacterial infection can help bacteria become resistant to the antibiotic so it won't work as well in the future.
It is important that antibiotics are taken as prescribed and for the right amount of time. If antibiotics are stopped early, the bacteria may develop a resistance to the antibiotics and the infection may come back again.
Note: Most colds and acute bronchitis infections will not respond to antibiotics. Health Home Conditions and Diseases. There are two main parts of the immune system: The innate immune system, which you are born with. These two immune systems work together. The innate immune system This is your child's rapid response system. Many health services are now offering SCIg therapy to eligible patients with specific immune conditions.
If you are interested, please discuss your particular requirements with your treating specialist. Immunisation works by copying the body's natural immune response. A vaccine a small amount of a specially treated virus, bacterium or toxin is injected into the body. The body then makes antibodies to it. If a vaccinated person is exposed to the actual virus, bacterium or toxin, they won't get sick because their body will recognise it and know how to attack it successfully.
Vaccinations are available against many diseases, including measles and tetanus. The immunisations you may need are decided by your health, age, lifestyle and occupation. Together, these factors are referred to as HALO, which is defined as:. View the HALO graphic to find out more. This page has been produced in consultation with and approved by:. For unexpected after-hours medical issues, there are telephone helplines, pharmacies, after-hours medical clinics or doctors who can visit you at home.
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Skip to main content. Immune system. Home Immune system. Immune system explained. Actions for this page Listen Print. Summary Read the full fact sheet. 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 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:. These cells surround and absorb pathogens and break them down, effectively eating them. There are several types, including:. 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:. The immune system needs to be able to tell self from non-self. It does this by detecting proteins that are found on the surface of all cells. It learns to ignore its own or self proteins at an early stage. In many cases, 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. Antibodies are special proteins that lock on to specific antigens. Numerous unnamed lymph nodes also exist throughout the body; in fact, virtually every corner of our body has some group of lymph nodes associated with it.
Lymph nodes tend to be most prevalent in areas near body openings, such as the digestive tract and the genital region, because this is where pathogens most often enter the body. If the immune system is a police force, lymph nodes are their stations. Once a pathogen is detected, nearby lymph nodes, often referred to as draining lymph nodes, become hives of activity, where cell activation, chemical signaling, and expansion of the number of immune system cells occur.
The result is that the nodes increase in size and the surrounding areas may become tender as the enlarged nodes take up more space than usual. But, the same thing can occur anywhere lymph nodes are activated. The spleen is the largest internal organ of the immune system, and as such, it contains a large number of immune system cells. Indeed, about 25 percent of the blood that comes from the heart flows through the spleen on every beat. As blood circulates through the spleen, it is filtered to detect pathogens.
As pathogens are detected, immune system cells are activated and increase in number to neutralize the pathogen. The spleen is particularly important in protecting people from bacterial infections, such as meningococcus and pneumococcus.
So, while people can live without a spleen, it is important for them to be up to date on vaccines that protect against these infections because they are at greater risk of suffering from them. Sometimes the skin is described as the largest organ of the immune system because it covers the entire body. People may not think about the skin as being part of this system, but the reality is that skin serves as an important physical barrier from many of the disease-causing agents that we come into contact with on a daily basis.
The innate immune system is the first line of defense against pathogens. In our example, the innate immune system is like the cops that patrol local beats. They take care of most of the criminal activity that takes place in a community and generally keep the peace. Similarly, most of the time our innate immune system effectively wards off infections by keeping pathogens in check.
This is accomplished in several ways. Our bodies physically ward off many potential pathogens. As mentioned above, our skin is an important protective barrier. These cellular intersections are called tight junctions. Our skin also tends to be dry and tough making it difficult for pathogens to gain entry. Epithelial cells that line openings into our bodies, such as the nose and mouth as well as throughout the respiratory, digestive, and genital tracts, tend to have one or more additional protective features.
First, the epithelial cells in these regions are coated with mucus, a thick, sticky solution that makes it difficult for pathogens to attach to them. Second, some of them also have microfibers, called cilia, which move the mucus and any pathogens in the mucus along the cell surface. Hairs in the nasal cavity work in a similar manner to trap pathogens in the air before they get into the lungs.
Our bodies also use muscles to move air and liquids to keep pathogens from infecting us. Sneezing, watery eyes, vomiting and diarrhea are all examples of our innate immune system working to protect us. Mucus not only provides a physical barrier, it also contains chemicals that help protect us from pathogens. Epithelial cells also secrete chemicals that prevent infection.
This is true of epithelial cells on our skin and in our digestive, respiratory, and genital tracts. Our body also uses chemical factors, such as acid, to create harsh environments for some pathogens. For example, the stomach has an acidic pH that makes it difficult for many viruses to survive the journey through the digestive tract. Bacteria live in and on us. As humans evolved, so did the bacteria that live on us. As a result, they are able to survive on our skin or in our digestive tract without our immune systems acting to rid them.
For example, while Staphylococcus bacteria are generally harmless on our skin, if they enter our bodies, they can be troublesome. In some cases, the disturbance is minor, such as a pimple. In other cases, the result can be deadly, such as a bloodstream infection. You may be wondering, then, why does our immune system allow these bacteria to be around at all? Like with other things in life, the answer comes down to a risk-benefit ratio.
When these bacteria are covering the surface of our skin or digestive tract, more harmful bacteria have less of an opportunity to do so. Additionally, commensal bacteria can help create conditions in the local environment that keep infectious agents from causing problems.
For example, commensal bacteria may release chemicals that are toxic to other types of bacteria. Evidence for the importance of these bacteria can be seen after taking oral antibiotics. You may have loose stools or intestinal cramping for a few days. This is because antibiotics, such as penicillin, can kill many different types of bacteria — good and bad.
A final way that the innate immune system works is through immune system cells.
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