 |
Discover ~ Translate ~ Cure |
 |
|
Discover ~ Translate ~ Cure |
|
The Immune System Basics |
|
| Our immune system protects our body from infection. The immune system is composed of specialized cells that recognize any threatening attack from foreign invaders such as bacteria or viruses. Some medical conditions in which people do not have a normal immune system can predispose them to increased risk of certain infections. Examples of this include some inherited immune deficiencies and diseases like HIV (AIDS) that attack the immune system. Sickness and death associated with AIDS, for example, is typically the result of an uncontrolled infection. Also, certain medications (such as those used following organ transplant) may cause chronic suppression of the immune system which may be associated with increased risks of infection.
The major protective response mounted by the immune system comes from the white blood cells. There are two main types of immunity: innate, and adaptive. Innate immunity is the non-specific protection against microbes we get from having intact skin and gut lining, as well as the protection provided by certain white blood cells called "phagocytes". Phagocytes are white blood cells such as granulocytes (or "polys") that destroy bacterial microbes in a non-specific fashion. The other type of immunity, adaptive immunity, provides more specific immunity against foreign invaders. Adaptive immunity is very specific for distinct molecules and is able to generate memory for those molecules. The effector cells of the adaptive immune response are called lymphocytes. |
|
| Lymphocytes provide important protection against potentially pathogenic organisms. There are two types of lymphocytes: B lymphocytes (B cells) and T lymphocytes (T cells). The B cells are responsible for antibody production. Antibody molecules may bind to antigens and cause destruction of bacteria, fungus, and viruses. T cells work in different ways. There are two types of T cells: helper T cells, and cytolytic (killer) T cells, also known as CTL. Helper T cells release cytokines when they confront fragments of immunogenic proteins. These cytokines naturally help boost the immune response.
CTL will directly kill a cell expressing an immunogenic protein. (see graphic) Phagocytes are white blood cells such as granulocytes (or "polys") that destroy bacterial microbes in a non-specific fashion. The other type of immunity, adaptive immunity, provides more specific immunity against foreign invaders. Adaptive immunity is very specific for distinct molecules and is able to generate memory for those molecules. The effector cells of the adaptive immune response are called lymphocytes. |
))
Antigen Presenting Cell Activating a Naive CD4 T Cell Graphic courtesy of Gary E. Kaiser (click for animation) |
| Thus, T cells help B cells make antibodies, or they can directly kill cells that they recognize to be infected. Infected cells may be identified by the immune system if they contain proteins that can act as antigens. Foreign substances that induce specific immune responses are called antigens. Proteins are important building blocks in all living cells and may sometimes act as antigens. Cells contain many types of proteins, though not all proteins are recognized by the immune system. Each encounter with a foreign antigen stimulates increasingly effective defense mechanisms called memory immunity and is the basis for booster immunization.
The way that T cells recognize and process antigen depends most often on a person's "human leukocyte antigen" (HLA) type. HLA proteins are present on the surface of most cells of the body and serve as identifiers that help lymphocytes distinguish normal from foreign cells. HLA type can be determined through a blood test and is similar to the blood type testing that a person might have before receiving a blood transfusion. |
CTL will directly kill a cell expressing an immunogenic protein
Graphic courtesy of Gary E. Kaiser |
Page last updated 3/25/09 |
|