The adaptive immune system targets pathogens and remembers them to fight them better in the future. The innate immune system is the body’s first reaction to a pathogen. Lymphocytes make up the adaptive immune system and B cells produce antibodies while T cells attack pathogens directly. Vaccinations activate the adaptive immune system and autoimmune diseases can occur if the system mistakes useful substances as harmful.
The adaptive immune system is one of the two components of a vertebrate’s immune system. The other component, the innate immune system, activates the adaptive system, which targets pathogens and attempts to destroy them. What makes the adaptive immune system so valuable is its ability to remember the first one and recognize any subsequent infections caused by the same pathogen. Therefore, the adaptive immune system is better equipped to fight it every time. This makes most vertebrates, especially humans, quite hardy and less likely to be harmed by a subsequent infection, if they survive the initial infection.
One component of the dual immune system of vertebrates is the innate immune system. It is the more primitive of the two and is the body’s first reaction to a pathogen, which is an organism that can produce disease. Unlike the adaptive immune system, the innate system consists of a set of automatic defenses that are not specific to a type of pathogen.
If the innate immune system fails to eradicate a pathogen, the adaptive immune system is activated. The adaptive immune system is particularly well suited to detect harmful antigens, which are all substances, including those found on pathogens, that trigger an immunological response when recognized as foreign to the body. Viruses and bacteria will trigger this process.
Lymphocytes make up the arsenal of the adaptive immune system against harmful antigens. These white blood cells travel through the body looking for foreign or harmful antigens. B cells and T cells are the body’s two approaches to counter harmful antigens.
B cells, also called B lymphocytes, are the humoral immune response (HIR) to antigens. This form of defense is characterized by the production of antibodies by B cells. The antibodies, which are actually proteins called immunoglobins, are dispensed from the B cell after it has identified a threat and attached itself to invading cells. The antibodies mark cells so that the innate immune system can target them, preventing pathogens and their toxins from attaching to host cells and reproducing.
T cells conduct cell-mediated immune responses, which refers to the ability of cells to attack pathogens directly, without antibodies. Cells with foreign antigens are targeted by T cells and killed before infection can take hold. They also activate other defense mechanisms, such as natural killer cells (NKC), which are found in the innate immune system. NKCs release proteins that cause death in the target cell.
Without an adaptive immune system, vertebrate life would suffer a much higher casualty rate from even the most common infections. When a lymphocyte detects a harmful antigen, its deoxyribonucleic acid (DNA), which gives a cell its distinctive characteristics, is permanently altered, meaning that the lymphocyte is now specialized in fighting against the specific pathogen.
The ability of cells to remember antigens is what makes vaccinations effective at preventing infection. Vaccinations activate the adaptive immune system. Lymphocytes discover the vaccine in the body and destroy it. White blood cells now recognize the pathogen and gear up to fight it.
The ability of the adaptive immune system to distinguish between the body and foreign harmful entities is key to proper immune function. If lymphocytes mistake a useful body part or foreign substance as harmful, then an autoimmune disease can develop. This causes the adaptive immune system to build a defense against necessary or useful substances and destroy them. The skin condition eczema is a common form of autoimmune disease.
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