The Immune System: An Easy Overview - Biology PDF

**Biology 6** **The Immune System: An Easy Overview** Name: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Class: \_\_\_\_\_\_\_ Date: \_\_\_\_\_\_\_\_\_\_\_\_\_\_ The immune system is very important for keeping our bodies healthy. It protects us from infections and diseases caused by harmful g...

**Biology 6** **The Immune System: An Easy Overview** Name: \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Class: \_\_\_\_\_\_\_ Date: \_\_\_\_\_\_\_\_\_\_\_\_\_\_ The immune system is very important for keeping our bodies healthy. It protects us from infections and diseases caused by harmful germs, like bacteria and viruses. The immune system is made up of different cells, tissues, and organs that work together to fight off these germs. It can tell the difference between our own cells and foreign invaders, allowing it to attack only the harmful ones. The immune system uses both general defenses, like barriers on our skin, and specific responses, using special cells called T cells and B cells. These cells help to destroy germs and remember them, so if they come back, the immune system can respond much faster. Overall, the immune system helps us stay healthy and fight off illnesses. **What causes infectious diseases?** [Pathogens] are tiny organisms that can make you sick, and there are different types of them. Bacteria are small, single-celled organisms that can multiply quickly and cause diseases like strep throat or food poisoning. Viruses are even smaller and need a living cell to grow; they can cause illnesses like the flu or COVID-19. Fungi, which include molds and yeasts, can lead to infections like athlete\'s foot. Parasites are organisms that live on or inside another living being, causing diseases like malaria. An infectious disease is when you get sick because of these pathogens invading your body and making you feel unwell. Types of pathogens, cellular, and non living virus organisms outline diagram. Collection with bacteria, parasites, fungi, prion or protozoa elements as risk for human immune system vector illustration Stock Vector \| Adobe **The Role of Antigens in Identifying Self vs. Non-Self** [Antigens] are special markers found on the surfaces of cells, and they help the immune system recognize what belongs to the body and what does not. Our own cells have unique antigens that identify them as "self." When the body encounters foreign pathogens, like bacteria or viruses, these invaders have different antigens that are recognized as "non-self." This recognition triggers an immune response. The immune system then activates certain cells to attack and destroy the foreign pathogens. This ability to tell the difference between self and non-self is very important for keeping us healthy and preventing infections. **Non-Specific (Innate) Immunity** Non-specific immunity, also known as innate immunity, is the body's first line of defense against infections. This type of immunity responds quickly to a wide range of harmful invaders, such as bacteria, viruses, and fungi. It is called \"non-specific\" because it does not target specific pathogens; instead, it provides general protection against any foreign threat. Several important components of non-specific immunity work together to keep us healthy. One of the most crucial barriers in non-specific immunity is the [skin]. The skin acts as a physical shield that prevents harmful microorganisms from entering the body. It is tough and resilient, making it difficult for pathogens to penetrate. Additionally, the skin produces oils and sweat that contain antimicrobial substances, further helping to kill germs that come into contact with it. Another important defense is [tears], which help protect our eyes. Tears contain enzymes, special proteins that can kill bacteria and wash away dirt and foreign particles, providing a vital safeguard for this sensitive area. The enzymes in [saliva] can also serve as defense from pathogens that enter the body that enter through the mouth. Saliva contains an enzyme that breaks down the cell walls of bacteria, helping to prevent infections in the mouth and throat. Similarly, [stomach acid] is a powerful barrier against pathogens. The strong acidity in the stomach destroys most harmful microorganisms that enter the digestive system, making it much harder for infections to take hold. In addition to these barriers, the immune system uses [phagocytes (macrophages)], which are specialized white blood cells. Phagocytes actively seek out and engulf harmful microorganisms. When they encounter pathogens, they surround and digest them, effectively removing the threat from the body.  Another important non-specific immune response is [inflammation], which occurs when tissues are injured or infected. Inflammation increases blood flow to the affected area, bringing more immune cells, like macrophages, to fight off the infection and promoting healing. Finally, a [fever] can occur as part of the body's immune response. When the body detects an infection, it may raise its temperature to create an environment that is less favorable for pathogens. Higher temperatures can also improve the effectiveness of immune cells. **Specific (Adaptive) Immunity** [Specific immunity], also known as [adaptive immunity], is the body\'s targeted response to specific pathogens. Unlike non-specific immunity, which acts quickly and generally, adaptive immunity develops over time and is designed to recognize and attack particular or specific invaders. This system relies on specialized cells called lymphocytes. There are two types of lymphocytes: [T cells] and [B cells]. When a pathogen enters the body, these cells identify a pathogen's unique antigens and prepare a precise response. The specific immune response involves several key steps and cells working together to identify and eliminate pathogens: 1\. The process begins when [macrophages], a type of immune cell, engulfing and digesting pathogens. They then display pieces of the pathogen, called antigens, on their surface. 2\. These macrophages present the antigens to [helper T cells]. When a helper T cell recognizes a specific antigen, it becomes activated and starts to multiply. 3\. Activated helper T cells release signals (cytokines) that activate B cells, another type of immune cell, to grow and divide. Some of these [B cells] will begin to produce antibodies specific to the pathogen. 4\. The activated helper T cells also stimulate [killer T cells (cytotoxic T cells)]. These cells are trained to identify and destroy infected or abnormal cells by recognizing the pathogen's antigens presented on the surfaces of body cells. 5\. B cells release antibodies that bind to the pathogens, marking them for destruction, while killer T cells seek out and destroy infected cells.  6\. After the infection is cleared, some B cells become memory cells. Memory B cells keep the information about the specific pathogen, allowing for a quicker and stronger response if the same pathogen invades the body again in the future. This coordinated response ensures that the body can effectively fight off infections and build lasting immunity. **The Power of Modern Medicine** Antibiotics, antivirals, antifungals, antiparasitics, and vaccines are important tools in medicine used to prevent and treat infections caused by different types of pathogens. [Antibiotics] are medications (drugs) that fight bacterial infections by killing bacteria or stopping their growth. They are effective against diseases like strep throat and bacterial pneumonia but do not work against viruses. A common antibiotic is penicillin, shown in the image below. Antibiotics \| Cambridge O Level Biology Revision Notes 2023 [Antivirals] are medications (drugs) designed to treat viral infections. They help by stopping viruses from multiplying in the body. Examples include medications for the flu and HIV. Antivirals do not cure viral infections but can help manage symptoms and reduce the severity of the illness. [Antifungals] are used to treat infections caused by fungi. They work by killing or stopping the growth of fungal cells. Common antifungal treatments are used for conditions like athlete\'s foot and yeast infections. [Antiparasitics] are medications (drugs) that target parasitic infections, such as those caused by worms or protozoa. They help to eliminate the parasites from the body, treating diseases like malaria and giardiasis. [Vaccines] are preventative measures that help the immune system recognize and fight specific pathogens. Some vaccines prevent bacterial infections, while others prevent viral infections. These are used to protect the body before an infection. Vaccines work by introducing a harmless part of the pathogen (like a protein or weakened form) into the body, prompting the immune system to build a defense of antibodies. Vaccines can prevent diseases such as measles, polio, and small pox.  Together, these treatments and preventive measures play a crucial role in maintaining health and controlling infectious diseases. Innate and adaptive immunity are two parts of the immune system that respond to infections at different speeds. Innate immunity is the body\'s first defense and acts quickly, usually within minutes to hours. It includes barriers like skin and immune cells such as macrophages that attack many types of pathogens in a general way. On the other hand, adaptive immunity takes longer to respond, often days to weeks after the first infection. It involves specific immune cells, like T cells and B cells that recognize particular pathogens. This response leads to the production of antibodies and memory cells, allowing for a faster response if the same pathogen infects the body again. In short, innate immunity is quick and broad, while adaptive immunity is slower but more targeted and lasting.