Immune System Quiz

An important defense against disease in vertebrate animals is the ability to eliminate, inactivate, or destroy foreign substances and organisms. Explain how the immune system achieves all of the following.

1. Provides an immediate nonspecific immune response
2. Activates T and B cells in response to an infection
3. Responds to a later exposure to the same infectious agent
4. Distinguishes self from nonself 

 The immune response is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful.The immune system protects the body from possibly harmful substances by recognizing and responding to antigens. Antigens are substances (usually proteins) on the surface of cells, viruses, fungi, or bacteria. Nonliving substances such as toxins, chemicals, drugs, and foreign particles (such as a splinter) can also be antigens. The immune system recognizes and destroys substances that contain antigens.Your own body's cells have proteins that are antigens. These include a group of antigens called HLA antigens. Your immune system learns to see these antigens as normal and usually does not react against them. 

1. 

The immune system protects you from dying from infection with layered defenses of increasing specificity. 

Physical barriers prevent pathogens such as bacteria and viruses from entering the body. 

If a pathogen breaches these barriers, the innate immune system provides an immediate, but non-specific response. Innate, or nonspecific, immunity is the defense system with which you were born. It protects you against all antigens. Innate immunity involves barriers that keep harmful materials from entering your body. These barriers form the first line of defense in the immune response. Examples of innate immunity are cough reflex, enzymes in tears and skin oils, skin, and stomach acid. 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.

2. 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.

Lymphocytes are a type of white blood cell. There are B and T type lymphocytes.

• B lymphocytes become cells that produce antibodies. Antibodies attach to a specific antigen and make it easier for the immune cells to destroy the antigen.

• T lymphocytes attack antigens directly and help control the immune response. They also release chemicals, known as cytokines, which control the entire immune response.

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. 

Here you can watch a video on Immune Response! 

The immune system includes specialized white blood cells, called lymphocytes that adapt themselves to fight specific foreign invaders. These cells develop into two groups in the bone marrow.

From the bone marrow, one group of lymphocytes migrates to a gland called the thymus and become T lymphocytes or T cells. Within the thymus, the T cells mature under the influence of several hormones.

The T cells mature into several different types, including helper, killer and suppressor cells. T cells are responsible for cell-mediated immunity. This type of immunity becomes deficient in persons with HIV, the virus that causes AIDS, because HIV attacks and destroys helper T cells.

The other group of lymphocytes, B lymphocytes or B cells, mature and develop within the bone marrow itself. In that process, they achieve the ability to recognize specific foreign invaders. From the bone marrow, B cells migrate through the body fluids to the lymph nodes, spleen and blood. B lymphocytes provide the body with humoral immunity as they circulate in the fluids in search of specific foreign invaders to destroy.

3. The immune system creates memory B cells that remember the foreign substance and it begins immune responses to fight off the infectious agent. These memory cells are able to recognize the threatening pathogens and are able to quickly and easily attack and kill. A primary immune response happens the first time that the body encounters a specific antigen. It takes several days to begin and one or two weeks to reach maximum activity. A secondary immune response occurs if the body encounters the same antigen at a later time. It takes only hours to begin and may peak within a few days. The invader is usually removed before it has a chance to cause disease. This is because some of the cloned T _C cells and B cells produced during a primary immune response develop into memory cells. These cells immediately become activated if the antigen appears again. 

4.  At the heart of the immune response is the ability to distinguish between "self" and "non-self." Every cell in your body carries the same set of distinctive surface proteins that distinguish you as "self." Normally your immune cells do not attack your own body tissues, which all carry the same pattern of self-markers; rather, your immune system coexists peaceably with your other body cells in a state known as self-tolerance. This set of unique markers on human cells is called the major histocompatibility complex (MHC). There are two classes: MHC Class I proteins, which are on all cells, and MHC Class II proteins, which are only on certain specialized cells. 

Any non-self substance capable of triggering an immune response is known as an antigen. An antigen can be a whole non-self cell, a bacterium, a virus, an MHC marker protein or even a portion of a protein from a foreign organism. The distinctive markers on antigens that trigger an immune response are called epitopes. When tissues or cells from another individual enter your body carrying such antigenic non-self epitopes, your immune cells react. This explains why transplanted tissues may be rejected as foreign and why antibodies will bind to them.