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Amith Raghav Chakravarthi

The Human Immune System

The task of the immune system is to recognize foreign material when it shows up in the body, and then to raise an overwhelming attack against that particular material. The immune system attacks both foreign organisms, such as bacteria, fungi, and viruses (if they can be called organisms), as well as foreign substances, such as proteins. The immune system is complicated and contains many cell types, as well as non-cellular components. Immune system cells circulate in the blood and are collectively known as white blood cells. There are two cell types most relevant here - B cells and T4 cells.
T4 cells regulate the entire immune system in several ways. They produce hormones that activate and control other parts of the immune system. They also give the confirming signal to other immune system cells, assuring them that the material they have encountered is indeed foreign and they may go ahead and attack it. Without functional T4 cells, the other components of the immune system are unable to attack any new materials, although ongoing immune responses can continue.
B cells circulate in the blood scouring it for foreign materials. Each B cell is sensitive to a very particular type of material. Most proteins can be recognized by only about 0.01% of all the B cells in the body. When a B cell encounters a protein of a type it recognizes, it internalizes the protein. After receiving confirmation from a T4 cell that the protein is indeed foreign, the B cell begins making antibodies to the protein.
The B cell releases antibodies into the bloodstream where the antibodies bind specifically and tightly to the same type of protein the B cell recognized. The antibodies stay bound to that protein and act as a red flag to other parts of the immune system. Anything bound by antibodies is labeled as a foreign invader and destroyed.
Once a B cell begins making antibodies to a specific protein, it will continue to do so, without additional signalling, as long as that protein is...

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