NOTES: Specific Defenses / Immunity (UNIT 10 part 3)

ANTIGENS… • ANTIGENS: specific foreign molecules that trigger an immune response; usually located on a cell’s surface -antigens include: proteins glycoproteins polysaccharides glycolipids toxins (venom, produced by bacteria)

ANTIGENS… • lymphocytes (B and T cells) develop receptors during embryonic development that allow them to distinguish between nonself (foreign) and self antigens

Notice the receptors look identical for the B and T cell. DURING EMBRYONIC DEVELOPMENT… Notice the receptors look identical for the B and T cell.

ANTIGENS… • nonself antigens combine with T cell and B cell surface receptors and activate these cells; this begins a specific immune reaction (your 3rd line of defense)

REVIEW QUESTION: What was the generic anatomical term for “white blood cell?” Erythrocyte Lymphocyte Leukocyte Fibroblast

LYMPHOCYTES (T and B Cells) • originate in the red bone marrow • some are released into the blood before they differentiate (specialize) -these reach the THYMUS, where they mature into T CELLS • others, the B CELLS, mature in the RED BONE MARROW • both T cells and B cells reside in lymphatic tissues and organs (lymph nodes, spleen, etc.)

LYMPHOCYTE FUNCTIONS **a lymphocyte must be ACTIVATED before it can respond to an antigen**

Activating the 3rd Line of Defense: 1st line and 2nd line of defenses have failed As part of 2nd line of defense, macrophages and dendritic cells have engulfed and destroyed pathogen Parts of the pathogen (antigen) move to the surface of the phagocytic cell Called antigen presentation

Activating the 3rd Line of Defense: When phagocytic cell randomly bumps into correct/ matching Helper T-cell, this activates the Helper T-cell

T CELLS and the CELLULAR IMMUNE RESPONSE Activated Helper T-cell divides into an army of Helper T-cell clones antigen T cell! Antigen Presenting Cell (APC)

T-CELLS ● Helper T-cells secrete chemicals that enhance cellular response to antigens Cause other T-cells and B-cells to divide and/or produce more chemicals “army” of TH move through circulatory & lymphatic system These chemicals and the antigen activate the specific Cytotoxic T-cell

T-CELLS ● Cytotoxic T-cells interact with and destroy the cells of your body that are infected (ex: throat cells invaded by cold virus) CELLULAR RESPONSE ● Cytotoxic T-cells secrete toxins (PERFORIN) that cause the cell to burst (lyse) which kills infected body cells  this destroys bacteria and immature viruses inside

T-CELLS ● Like macrophages, your infected body cells will also present antigen but Cytotoxic T-cells can tell the difference between an infected body cell & a macrophage presenting antigen -recognize nonself antigens on cancer cells or virus- infected cells

B-CELLS ● specific B-cell also needs to be activated by the specific Helper T-cells ● Once the specific Helper T-cell randomly bumps into the specific B-cell, contact and chemicals will activate the correct B-cell  B-cells divide into clones! HUMORAL IMMUNE RESPONSE ● activated B-cell (called a plasma cell) will produce antibodies & memory cells for later

● activated B cells specialize into PLASMA CELLS (antibody-producing cells) *(antibodies react against the antigen that stimulated their production) AND ● activated B cells also differentiate into MEMORY B CELLS (respond to subsequent exposures of the same antigen)

T and B cells… **each person has millions of varieties of T and B cells BUT only a few of each variety (receptor shape) **once a specific cell has been activated, that cell CLONES itself to make lots of copies of the correct antigen fighting cell** **Therefore, each type of T cell or B cell has a particular type of antigen receptor that can respond only to a SPECIFIC antigen**

REVIEW QUESTION: What cellular process results in clones? Mitosis Meiosis Mutation Fragmentation

TYPES OF ANTIBODIES ● antibodies are proteins called IMMUNOGLOBULINS (Ig) ● 5 major types or classes of antibodies: IgG, IgA, IgM, IgD, and IgE.

IgG

ANTIBODY ACTIONS ● antibodies work by: attacking the antigens directly (attaching to antigen) -cause them to clump together (AGGLUTINATION) or form insoluble masses (PRECIPITATE) -makes it easier for phagocytes to engulf the antigens / antigen-bearing agents & eliminate them

Agglutination

ANTIBODY ACTIONS 2) stimulate changes in local areas that help prevent the spread of the antigens (ex: promote inflammation)

REVIEW QUESTION: The humoral response involves B cells, Cytotoxic T cells, and antibodies B cells, and antibodies Cytotoxic T cells and perforin B and C

REVIEW QUESTION: The function of Helper T-cells is to Produce antibodies Engulf and destroy pathogens Destroy infected cells Activate both the cellular response & humoral response

REVIEW QUESTION: Which of the following are antigen presenting cells (APC)? Infected body cell Body cell that has become cancerous Macrophage that has engulfed & destroyed a pathogen All of the above are antigen presenting cells

REVIEW QUESTION: A B-cell that has been activated will undergo mitosis and make clones of itself. What happens to some of those B-cells next? They differentiate into a plasma cell and make antibodies They start releasing perforin to destroy infected cells They are selected for destruction They move into the bloodstream and release antigen