• Lymphatic vessels transport fluids that have escaped from the blood vascular system back to the blood
  
  • Lymphoid organs house phagocytic cells and lymphocytes that help in body defense and resistance to disease.

• recognizes foreign molecules and acts to inactivate or destroy them
• Is the body's third line of defense that protects the body from from a variety of pathogens

• small masses of lymphatic tissue that ring the pharynx where they are found in the mucosa
• Job is to trap and remove any bacteria or other foreign pathogens
• Sometimes become congested with bacteria and become red, swollen, and sore (tonsillitis).

-found in wall of small intestine

• Macrophages pf Peyer's Patches are in an ideal positions to catch and kill bacteria, allowing to prevent them from penetrating the intestine wall

• Function is to pick up excess tissue fluid (lymph) and return it to the bloodstream - form a one way system and lymph flows only towards the heart -

• Help protect the body by removing foreign material like bacteria and tumor cells from the lymphatic stream and producing lymphocytes that function in the immune response
  
  • As lymph is transported towards the heart, it becomes filtered through the lymph nodes that cluster along the lymphatic vessels
  • Within the lymph nodes, macrophages are found which destroy viruses, bacteria and other foreign substances before its returned into the blood.

• functions at peak levels during youth, and is a lymphatic mass found low in the throat overlaying the heart
• produces hormones, thymosin, and others that function in the programing of certain lymphocytes so they can carry out their protective roles in the body

• Blood-rich organ that filters blood
• located in the left side of the abdominal cavity and extends to curl around the anterior aspect of the stomach
• Spleen filters the and cleanse the blood of bacteria, viruses and other debris
• Most important function is to destroy worn-out red blood cells and return some of their breakdown products to the liver

-Antibodies defend against infection in body fluids

• Lymphocytes that mature in the bone marrow are called B-cells and are involved in the humoral immune response
• Both T-cells and B-cells have receptor proteins to bind antigens
• each individual lymphocytes are designed to recognize to a specific type of antigen

-Reintroduction of antigen at future time

• much faster, stronger, more efficient, and longer lasting than primary
• Destroys pathogen before any symptoms of infections shows
  -Memory cells become activated as soon as antigens is reintroduced into the body

-Owns body's B-Cells have to make antibodies and memory cells
-2 types :

• Naturally acquired active-Making antibodies during an illness or infection in normal circumstances
• Artificially acquired active-making antibodies by an injection such as vaccines

-Antibodies are obtained from someone else but memory doesn't occur
-2 types:

• Naturally acquired Passive-normal passing of antibodies from mother to fetus
  - Artificially acquired Passive-receive injection of immune serum or antibodies

-cytotoxic cells defend against infection in already infected, cancer, or transplanted cells
-Lymphocytes that mature in the thymus are called T-cells and are involved in the cell-mediated immune response

-T-cells cant bind to antigens

• Antigens must be presented by macrophages to an immunocompetent T-Cell
  
  • Major histocompatibility complex(MHC) proteins are pieces of cellular material on the cell surface (gives cell unique label)
    -Cells, macrophages, or even plasma cells can digest pathogens and carry portions of the antigen on the MHC proteins
    -Any cells carrying the MHS with the portion of the antigen is called the Antigen Presenting Cell(APC)
    -T-cells recognize and binds to the infected or cancerous cells by the complex (MHC) proteins
• After binding, clones are formed of the different types of T-cells

-Helper T-cell: Alerts and recruits rest of the immune system including the humoral immunity
-Killer (cytotoxic) T-cells: Specialized in attacking and killing cells by releasing a toxic chemical Perforin
-Suppressor T-cell:

• release chemical, suppressor factor, to suppress activity of T and B cells
• stops immune response to prevent uncontrolled activity
  -Memory T-cells: few members of each clones provide long-term immunity

-Chemicals released by antigen presenting cells or T-cells that stimulates other T-cells
-Monokines -Released by macrophages or antigen presenting cells
- interleukin 1-Stimulates T-cells
-Lymphokines-Released by T-cells
- interleukin 2-stimulates T and B cells to proliferate/ multiply

• Perforin-Released by killer T-cells

-AKA immunoglobin or Ig

• Soluble proteins secreted by the plasma cells derived from the B-cells
• Carried in the body fluids - Capable of binding specifically to antigens

-Made up of 4 amino acid chains linked by a disulfide bond
-2 light amino chains
-2 heavy amino chains made by 2 identical amino chains linked together
-2 variable region makes up the antigen-binding site
-Antigen-binding sites specific to the antigen
-Constant portion is the same to all antibodies

-Antibodies of each class have slightly different roles
-5 major classes:
-IgM-Primary immune response
-IgA-found primarily in mucus
-IgD-Important to the activation of B-cells
-IgG-can cross placental barrier
-IgE-involved in allergies

-Complement Fixation: occurs when complement proteins attach to the antigen or foreign substance such as bacteria and activates immunity
-Opsonization: Some act as labels to be identified by other immune cells for phagocytosis
-Neutralization: Some work as antitoxins, blocking the effects of the poison produced by certain bacteria
-Angulation: Some clump with other antibodies to form clots in blood, used for blood typing
-Precipitation: antigen-antibody complex becomes so large it is insoluble and less likely to spread

-Used for research, clinical testing for diagnosis of diseases, and treating certain types of cancers

• Deliver cancer fighting drugs to cancerous cells - Diagnosis of pregnancy
• Treatment after exposure to hepatitis and rabies

-Antibody generator-any substances capable of activating immune system by eliciting an immune response

• EX: foreign proteins, nucleic acids, large carbohydrates, some, lipids, pollen grains, microorganisms

-Human cells have many surface proteins
-Our immune cells don't attack our won proteins
-Our cells in another persons body can trigger an immune response because they are foreign
-Restricts donors for transplants(organ rejection)

-allergies
-Auto immune disease

• Lupus
  -Aids
  -HIV
  -Asthma -