Immune response

Answer 1

Definition

The immune response is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful.

Alternative Names

Innate immunity; Humoral immunity; Cellular immunity; Immunity; Inflammatory response; Acquired (adaptive) immunity

Information

The immune system protects the body from potentially harmful substances by recognizing and responding to antigens. Antigens are molecules (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 these antigens.

Even 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.

INNATE IMMUNITY

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 include:

• Coughreflex
• Enzymes in tears and skin oils
• Mucus, which traps bacteria and small particles
• Skin
• 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.

ACQUIRED IMMUNITY

Acquired immunity is immunity that develops with exposure to various antigens. Your immune system builds a defense that is specific to that antigen.

PASSIVE IMMUNITY

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 6 and 12 months of age.

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.

BLOOD COMPONENTS

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 cells produce antibodies. Antibodies attach to a specific antigen and make it easier for the immune cells to destroy the antigen.
• T cells 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, and in many cases 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.

INFLAMMATION

The inflammatory response (inflammation) occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause. The damaged cells release chemicals including histamine, bradykinin, and prostaglandins. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling. This helps isolate the foreign substance from further contact with body tissues.

The chemicals also attract white blood cells called phagocytes that "eat" microorganisms and dead or damaged cells. This process is called phagocytosis. Phagocytes eventually die. Pus is formed from a collection of dead tissue, dead bacteria, and live and dead phagocytes.

IMMUNE SYSTEM DISORDERS AND Allergies

Immune system disorders occur when the immune response is inappropriate, excessive, or lacking. Allergies involve an immune response to a substance that most people's bodies perceive as harmless.

For more information, see:

• Allergies
• Autoimmune disorders
• Immunodeficiency disorders

IMMUNIZATION

Vaccination (immunization) is a way to trigger the immune response. Small doses of an antigen, such as dead or weakened live viruses, are given to activate immune system "memory" (activated B cells and sensitized T cells). Memory allows your body to react quickly and efficiently to future exposures.

COMPLICATIONS DUE TO AN ALTERED IMMUNE RESPONSE

An efficient immune response protects against many diseases and disorders. An inefficient immune response allows diseases to develop. Inadequate, inappropriate, or excessive immune response causes immune system disorders.

Complications related to altered immune responses include:

• Allergy or hypersensitivity
• Anaphylaxis
• Autoimmune disorders
• Blood transfusion reaction
• Disease development
• Graft versus host disease
• Immunodeficiency disorders
• Serum sickness
• Transplant rejection

References

Firestein GS. The inflammatory response. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 45.

Goronzy JJ, Weyand CM. The innate and adaptive immune systems. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 42.

Answer 2

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.

Reviewed By

Review Date: 11/16/2010

Paula J. Busse, MD, Assistant Professor of Medicine, Division of Clinical Immunology, Mount Sinai School of Medicine, New York, NY, Review provided by VeriMed Healthcare Network.

Answer 3

Definition

The immune response is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful.

Alternative Names

Innate immunity; Humoral immunity; Cellular immunity; Immunity; Inflammatory response; Acquired (adaptive) immunity

Information

The immune system protects the body from potentially harmful substances by recognizing and responding to antigens. Antigens are molecules (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 these antigens.

Even 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.

INNATE IMMUNITY

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 include:

• Coughreflex
• Enzymes in tears and skin oils
• Mucus, which traps bacteria and small particles
• Skin
• 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.

ACQUIRED IMMUNITY

Acquired immunity is immunity that develops with exposure to various antigens. Your immune system builds a defense that is specific to that antigen.

PASSIVE IMMUNITY

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 6 and 12 months of age.

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.

BLOOD COMPONENTS

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 cells produce antibodies. Antibodies attach to a specific antigen and make it easier for the immune cells to destroy the antigen.
• T cells 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, and in many cases 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.

INFLAMMATION

The inflammatory response (inflammation) occurs when tissues are injured by bacteria, trauma, toxins, heat, or any other cause. The damaged cells release chemicals including histamine, bradykinin, and prostaglandins. These chemicals cause blood vessels to leak fluid into the tissues, causing swelling. This helps isolate the foreign substance from further contact with body tissues.

The chemicals also attract white blood cells called phagocytes that "eat" microorganisms and dead or damaged cells. This process is called phagocytosis. Phagocytes eventually die. Pus is formed from a collection of dead tissue, dead bacteria, and live and dead phagocytes.

IMMUNE SYSTEM DISORDERS AND ALLERGIES

Immune system disorders occur when the immune response is inappropriate, excessive, or lacking. Allergies involve an immune response to a substance that most people's bodies perceive as harmless.

For more information, see:

• Allergies
• Autoimmune disorders
• Immunodeficiency disorders

IMMUNIZATION

Vaccination (immunization) is a way to trigger the immune response. Small doses of an antigen, such as dead or weakened live viruses, are given to activate immune system "memory" (activated B cells and sensitized T cells). Memory allows your body to react quickly and efficiently to future exposures.

COMPLICATIONS DUE TO AN ALTERED IMMUNE RESPONSE

An efficient immune response protects against many diseases and disorders. An inefficient immune response allows diseases to develop. Inadequate, inappropriate, or excessive immune response causes immune system disorders.

Complications related to altered immune responses include:

• Allergy or hypersensitivity
• Anaphylaxis
• Autoimmune disorders
• Blood transfusion reaction
• Disease development
• Graft versus host disease
• Immunodeficiency disorders
• Serum sickness
• Transplant rejection

References

Firestein GS. The inflammatory response. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 45.

Goronzy JJ, Weyand CM. The innate and adaptive immune systems. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 42.

Reviewed By

Review Date: 05/02/2010

David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; and Stuart I. Henochowicz, MD, FACP, Associate Clinical Professor of Medicine, Division of Allergy, Immunology, and Rheumatology, Georgetown University Medical School. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.