However, they are important in mounting a non-specific immune response to pathogens, organisms that can cause disease. When stimulated, these cells release histamine, among other chemicals.
This can result in inflammation and narrowing of the airways. Lymphocytes are also essential in the immune system. They come in two forms: B cells and T cells. Unlike other white blood cells that provide non-specific immunity, B and T cells have specific purposes.
B lymphocytes B cells are responsible for humoral immunity, which is the immune response that involves antibodies. B cells produce the antibodies that "remember" an infection. They stand ready in case your body is exposed to that pathogen again. T cells recognize specific foreign invaders and are responsible for directly killing them. B lymphocytes play a key role in the effectiveness of many current vaccines. In some cases, such as tuberculosis and pertussis vaccines, T lymphocytes are the main players.
Monocytes are the garbage trucks of the immune system. Their most important function is to clean up dead cells in the body. Leukocytes, better known as white blood cells, take on different forms that perform different roles in the immune system. These include:. White blood cells begin in the bone marrow in a process called hematopoiesis. All blood cells descend from a common hematopoietic stem cell HSC. This is also called a "pluripotent" stem cell. These stem cells differentiate—or specialize—in different stages.
The HSC cell first separates into either a lymphoid or myeloid stem cell. The lymphoid stem cell gives rise to the lymphoid cell line. This is the family of cells that produces B cells and T cells. The myeloid stem cells give rise to cells called myeloblasts. These further evolve into macrophages, monocytes, neutrophils, basophils, and eosinophils. Myeloblasts can also turn into red blood cells and platelets. A normal white blood cell count is usually between 4, and 10, cells per microliter mcL.
Infections usually cause an elevated white blood cell count, but there are also other possible causes. WBC counts can be increased by overproduction. In other words, the body may release white blood cells early from the bone marrow. Stress of any form can result in this release of white blood cells. Some causes of an increased white blood cell count include:. In severe infections, immature white blood cells called blasts may be present.
Blasts often appear when the body attempts to get white blood cells on the scene quickly. Conditions that may result in a low white blood cell count include:. On its own, a low WBC count doesn't have symptoms. But a low count will often lead to an infection, because not enough white cells are present to fight off the invader. Symptoms of infection may include:. One of chemotherapy's most common and dangerous side effects is its effect on white blood cells known as neutrophils.
Recall that neutrophils are the first responders of our immune system. Examples of innate immunity include:. Innate immunity also comes in a protein chemical form, called innate humoral immunity. Examples include the body's complement system and substances called interferon and interleukin-1 which causes fever.
If an antigen gets past these barriers, it is attacked and destroyed by other parts of the immune system. Acquired immunity is immunity that develops with exposure to various antigens. Your immune system builds a defense against that specific antigen. Passive immunity is due to antibodies that are produced in a body other than your own.
Infants have passive immunity because they are born with antibodies that are transferred through the placenta from their mother. These antibodies disappear between ages 6 and 12 months. Passive immunization may also be due to injection of antiserum, which contains antibodies that are formed by another person or animal. It provides immediate protection against an antigen, but does not provide long-lasting protection.
Immune serum globulin given for hepatitis exposure and tetanus antitoxin are examples of passive immunization. The immune system includes certain types of white blood cells.
It also includes chemicals and proteins in the blood, such as antibodies, complement proteins, and interferon. Some of these directly attack foreign substances in the body, and others work together to help the immune system cells. As lymphocytes develop, they normally learn to tell the difference between your own body tissues and substances that are not normally found in your body. Once B cells and T cells are formed, a few of those cells will multiply and provide "memory" for your immune system.
This allows your immune system to respond faster and more efficiently the next time you are exposed to the same antigen.
In many cases, it will prevent you from getting sick. For example, a person who has had chickenpox or has been immunized against chickenpox is immune from getting chickenpox again. These cells therefore help the body reject organisms, such as viruses or tuberculosis bacteria, that exist inside cells. The ab T cells are also good at reacting with other cells of the immune system, such as B cells.
And the gd T cells react with damaged host cells. Although an invading organism may evolve so that it can avoid one of these methods of recognition, it is almost impossible for an invader to avoid all types of immunity. Therefore, higher vertebrates are well protected against most organisms. Newsletter Get smart. Sign up for our email newsletter. Already a subscriber? Sign in. Thanks for reading Scientific American.
Create your free account or Sign in to continue. See Subscription Options. In , Marrack and her husband, John W. Here is her reply. Image: University of Virginia. Get smart. Apply market research to generate audience insights. Measure content performance. Develop and improve products. List of Partners vendors. How Your Immune System Works. Was this page helpful? Thanks for your feedback!
Sign Up. What are your concerns? Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Related Articles. Here's a Quick Overview of Head Cold. How Long Is a Cold Contagious? Causes and Risk Factors of Colds. Common Infections in Cancer Patients.
Infections That Cause Headaches and a Fever.
0コメント