Understanding the Immune System

• The immune system defends the body against foreign invaders like bacteria, viruses, parasites, and fungi.
• When the immune system malfunctions, it can cause diseases like allergies, arthritis, or AIDS.
• Key to a healthy immune system is its ability to distinguish between the body's own cells (self) and foreign cells (nonself).
• Anything that triggers an immune response is called an antigen.
• Autoimmune diseases occur when the immune system mistakenly attacks the body's own cells or tissues.
• Allergens are antigens that cause allergies.

The Structure of the Immune System

• Lymphoid organs, which house lymphocytes, are positioned throughout the body.
• Bone marrow is the source of all blood cells, including white blood cells.
• The thymus is where T lymphocytes mature.
• Lymphocytes travel through the body using blood vessels and lymphatic vessels.
• Lymphatic vessels carry lymph, and monitor the body for invading microbes.
• Lymph nodes contain specialized compartments where immune cells congregate and encounter antigens.
• The spleen contains specialized compartments where immune cells gather and work.
• Lymphoid tissue clumps are found in the linings of the digestive tract, airways, and lungs.
• These include the tonsils, adenoids, and appendix.

Immune Cells and Their Products

• The immune system includes lymphocytes, phagocytes, and their relatives.
• Some immune cells target all threats, others are trained on specific targets.
• Stem cells in the bone marrow can develop into T cells, B cells, or phagocytes.
• Researchers are studying stem cells for their potential in treating immune system disorders.
• B cells secrete antibodies into the body's fluids.
• Antibodies ambush antigens in the bloodstream but cannot penetrate cells.
• Each B cell is programmed to make one specific antibody.
• When a B cell encounters its triggering antigen, it becomes a plasma cell.
• Plasma cells produce millions of identical antibody molecules.
• Immunoglobulins are a family of large antibody molecules.
  • IgG coats microbes
  • IgM kills bacteria.
  • IgA guards the entrances to the body
  • IgE is responsible for allergy symptoms.
  • IgD initiates early B-cell response.
• T cells do not recognize free-floating antigens; they see fragments of antigens on infected or cancerous cells.
• Helper T cells (Th cells) coordinate immune responses by communicating with other cells.
• Cytotoxic T lymphocytes (CTLs) directly attack other cells carrying foreign or abnormal molecules on their surfaces.
• NK cells recognize cells lacking self-MHC molecules and attack many types of foreign cells.
• Phagocytes swallow and digest microbes and other foreign particles.
• Monocytes are phagocytes that circulate in the blood and develop into macrophages in tissues.
• Macrophages rid the body of worn-out cells and display bits of foreign antigen to lymphocytes.
• Macrophages produce monokines, which are vital to immune responses.
• Granulocytes contain granules filled with chemicals to destroy microorganisms.
  • Neutrophils are phagocytes that use prepackaged chemicals
  • Eosinophils and basophils degranulate
• Mast cells in the lungs, skin, tongue, etc, are responsible for the symptoms of allergy.
• Cytokines are chemical messengers that coordinate immune responses
• Interleukin 2 (IL-2) triggers the immune system to produce T cells.
• Chemokines attract specific cell types to a site of injury or infection.
• The complement system consists of about 25 proteins that complement the action of antibodies in destroying bacteria.
• Complement proteins cause blood vessels to dilate and contribute to inflammation

Mounting an Immune Response

• Infections are a common cause of disease.
• Pathogens must move past external armor (skin) to get into the body.
• The skin is penetrable through cuts or abrasions only.
• Microbes entering the nose often cause nasal surfaces to secrete mucus.
• The stomach contains a strong acid that destroys many pathogens.
• Epithelial cells and mucosal surfaces block organism transport.
• Invaders must escape general defenses, including patrolling phagocytes, NK cells, and complement.
• Microbes that cross the barriers confront specific weapons, include antibodies and T cells
• Bacteria live in the spaces between cells and are attacked by antibodies.
• Antibodies send signals to destroy the bound microbes.
• Viruses must enter cells to survive.
• Infected cells use MHC molecules to flag down cytotoxic T lymphocytes to destroy the infected cell.

Immunity: Natural and Acquired

• Recovering from the plague would mean that you never got it again, this is acquired immunity.
• Activated T and B cells become memory cells, to set to demolish it the next time.
• Immunity strength depends on the type of antigen, amount of it, and the route by which it enters the body.
• Immunity is influenced by inherited genes.
• Vaccines are part of the microorganisms that have been treated to provoke an immune response but not disease.
• Immunity can be transferred via injection of serum
• Passive immunity lasts few weeks or months.
• Infants are protected because of antibodies received before birth, or antibodies from breast milk.
• Immune tolerance is the tendency of T or B lymphocytes to ignore the body's own tissues.
• Central tolerance occurs during lymphocyte development through clonal deletion.
• Peripheral tolerance occurs when T or B cell signals are absent in mature cells.

Vaccines

• Medical workers help with the body's immune system for attacks through vaccination.
• Vaccines consist of killed or modified microbes/components or microbial DNA that trick the body into thinking an infection has occurred.
• Prevents devastating diseases and have a safety record.
• Previously devastating diseases such as smallpox, polio, and whooping cough have been greatly controlled.

Disorders of the Immune System

• Allergic diseases happen when the immune system responds to a false alarm.
• Related to the antibody known as IgE
• Autoimmune Diseases happen when the recognition apparatus breaks down, and the body begins to manufacture T cells and antibodies.
• Factors of the cause could include viruses, environment, hormones, and heredity.
• Antibodies to many types of their own cells and cell components.
• Immune Complex Diseases are clusters of interlocking antigens and antibodies.
• Immune complexes are in the bloodstream then trapped in tissues such as the kidneys, lungs, skin, and joints.
• Immunodeficiency Disorders occurs when the system is missing one or more of its components.
• Can be inherited, acquired through infection, or produced due to treatment of cancer.
• temporary immune deficiencies are caused by virus infections such as influenza, infectious mononucleosis. Immune responses by blood transfusions, surgery, malnutrition, smoking, and stress.
• Severe combined immunodeficiency disease or SCID when infants are lacking of the defense cells.
• AIDS is from HIV that infects immune cells such as T cells, leading to variety of shortcomings.

Cancers of the Immune System

• Cells of the system that can grow uncontrollably = cancer
• Leukemias is when the proliferation of white blood cells, or leukocytes.
• Hodgkin's disease or lymphomas due to the organs.

Immunology and Transplants

• Transplanting organs prolong life
• Tissue typing makes makes sure markers of self on the donor's tissue are as similar Each cell has a double set of 6 major tissue antigens, and each of the antigens exists
• Another way is to lull the recipient's immune. Immunosuppressive drugs such as cyclosporine A
• Bone Marrow Transplants introduce into the circulation, transplanted bone marrow cells can develop into functioning
  • Graft-versus-host disease uses drugs or antibodies

Immunity and Cancer

• Cells become cancer, antigens on surface may change
• Launching the body's defenders, including killer T cells, NK cells, and macrophages.
• The system cannot patrol everywhere to provide bodywide surveillance, flushing out and eliminating all cells
• Using lymphocytes and lymphokines, to bolster the patient's immune responses.
• Injecting directly into the patient or transforming lymphocytes.
• Coupling with drugs, toxins, or radioactive materials, then sent off like "magic bullets" to deliver their lethal cargo.

Genetic Enginnering

• Pluck genes-segments of the hereditary. material; DNA-from one type of organism and combine them with genes of a second
• Introduce into cells taken from the patient's bone marrow. After treated marrow cells begin to produce the enzyme,

Immunoregulation

• Research into what control's the system can lead to knowledge of its functions.
• Transplanting immature human immune tissues or immune cells into SCID mice has created a model of the system.

Frontiers of Immunology

• Mass-produce immune cell secretions, both antibodies and lymphokines, as well as specialized immune cells.
• Monoclonal antibodies are promising treatments for a range of diseases.
• Mouse antibodies are "foreign" to people, and might trigger their own immune response when injected into a human.

The Immune System and the Nervous System

• When stress messages from the brain, the adrenal glands release hormones into the blood
• Hormones and other chemicals known to convey messages among nerve cells have been found to "speak” to cells of the immune Indeed, some immune cells are able to manufacture typical nerve cell products, while some lymphokines can transmit information to the nervous system
• Networks of nerve fibers have been found connecting to the lymphoid organs.