A&P II- Quiz 4 The Lymphatic System and Immunity

Functional Characteristics of Phagocytes

- Can leave capillaries by squeezing between endothelial cells called Emigration or Diapedisis - Phagocytes can be attracted to chemicals which is called Chemotaxis

Phagocytes

- Engulf and destroy foreign substance, pathogens, and cellular debris - "First line of cellular defense" against pathogenic invasion - Can attack and remove microorganisms even before lymphocytes detect their presence 1. Neutrophils (in bloodstream and tissues) - Abundant, mobile, fast-acting, Phagocytize cellular debris or bacteria 2. Eosinophils (less abundant than neutrophils) - Phagocytize foreign compounds and antibody-coated pathogens 3. Monocyte-macrophage system (reticuloendothelial system)

Inflammation or inflammatory response

- Localized tissue response to injury producing the cardinal signs and symptoms of inflammation •Local redness (rubor) •Swelling (tumor) •Heat (calor) •Pain (dolor) •Sometimes lost function (functiolaesa) Cause a change in chemical composition of the interstitial fluid. Caused by various stimuli that kill cells, damage connective tissue fibers, or injure tissue. Changes trigger complex inflammation response.

Combined components of immune system offer three lines of defense against pathogens:

1. First line of defense - includes cutaneous and mucous membranes that act as surface barriers to block entry of pathogens into body 2. Second line of defense - includes responses of cells and proteins that make up innate immunity 3. Third line of defense - includes responses of cells and proteins of adaptive immunity

Immune Surveillance

Constant monitoring of normal tissues by naturalkiller (NK) cells - NK cells recognize bacteria, foreign cells, virus-infected cells, and cancer cells - Cancer cells often contain tumor-specificantigens Immunological escape - Immune surveillance by NK cells is not perfect - Primary tumors may be surrounded by a capsule and escape detection - Daughter tumor cells sometimes do not display tumor-specific antigens or secrete chemicals that kill NK cells

What is Immunity?

The ability to fight infection, illness, and disease, Complementary mechanisms work independently and together

Types of Immunity

1. Innate (nonspecific) immunity - Responds same way to all- Quicker - Provides nonspecific resistance, Does not distinguish one type of threat from another, Response is the same regardless of type of invading agent - Present at birth (innate), Prevents the approach, denies the entry, limits the spread of microbes or other environmental hazards 2. Adaptive, or specific, immunity - Utilizes adaptive defenses, Protects against particular threats, Depends on the activities of specific lymphocytes, Produces state of protection known as specific resistance - Does not responds to all pathogens or classes of pathogen in same way, Components of adaptive, or specific, immunity respond individually to unique antigens - Not all of these cells can fight all pathogens; they can only respond to certain pathogens (so they are specific) - Coordinated and produced by T cells and B cells, Not present at birth, Acquired by:•Exposure to antigen•Active immunity 1. A pathogen or foreign substance "wakes up" the immune system when its antigens are detected by immune cells. 2. The pathogens are engulfed by phagocytes. Phagocytes activate T cells to fight the infection. 3. T cells fight pathogen through phatocytosis or chemical toxins that damage the pathogen. 4. In antibody mediated immunity, B cells are activated by macrophage; B cells produce antibodies. 5. Antibodies are released into interstitial fluid and attach to phathogen causing them harm. major histocompatibility complex (MHC) 1. Class I MHC proteins - Present in membranes of all nucleated cells•Triggered by viral or bacterial infection of a body cell

NK Cells - Fancy Active Defense

1. Presence of unusual plasma membrane activates NK cellNK cell adheres to target cell 2. Golgi apparatus moves within NK cell near target cell produces many secretory vesicles containing perforins 3. Perforins released from NK cell and arrive at target cell 4. Perforins create pores in target cell membraneTarget cell can no longer maintain its internal environment and disintegrates

Properties of Adaptive Immunity

1. Specificity - T cells and B cells have receptors for only one specific antigen - Responses of activated T cell or B cell are also specific (do not affect any other antigens) 2. Versatility - Millions of lymphocytes, each sensitive to a different antigen, When activated, a lymphocyte divides - Produces more lymphocytes with same specificity 3. Immunological Memory - Activated lymphocytes produce two groups of cells•Groups that attack invaders immediately - Group that remains inactive unless exposed to the same antigen later - These memory cells "remember" antigens, making future attacks faster, stronger, and longer-lasting 4. Tolerance - Immune response ignores "self" but targets abnormal and foreign "non-self" cells and toxins. Can develop over time in response to chronic exposure to an antigen

Antigens

Antigens are molecular markers that identify what type of cell they are. These markers are unique for each thing (not found anywhere else). So the body uses these unique parts of biologic molecules to identify and label the whole thing.

Complement System Cont.

Enhanced phagocytosis - Attracts phagocytes and makes target cells easier to engulf: Process called opsonization Histamine release - By mast cells and basophils, Increases inflammation and blood flow to region

Inflammation and Fever

Fever - Body temperature >37.2°C (99°F) - Pyrogens (pyro-, fever or heat, + -gen, substance) • Circulating fever-inducing proteins • Reset temperature thermostat in hypothalamus • Raises body temperature - Can be beneficial within limits • May inhibit some viruses and bacteria • Increases metabolic rate which may accelerate tissue defenses and repair process

Types of Immunity Information

Immunity is classified according to way it responds to different pathogens or forms of cellular injury: - Innate, or nonspecific, immunity responds to all pathogens or classes of pathogen in same way ---Innate immune system consists of certain immunological cells that respond quickly ----- dominant response to pathogens for first 12 hours after exposure Cells exist in bloodstream, even in absence of a stimulus

Mixed vs. Free Macrophages

Macrophages (derived from monocytes) - Fixed macrophages: (scattered among connective tissues; immobile within those tissues) - Freemacrophages: (travel throughout body)

Interferons

Molecules that are released from virus infected cells. - Cause surrounding cells to become more resistant to viral replication. - Also attract NK cells and macrophages - which can kill infected cells before the virus replicates and destroys the cell. Bad for the infected cell (dead), good for the organism (stops the spread of the virus).

Interferons and the Complement System

Name refers to the fact that the system complements the action of antibodies Over 30 special proteins form this system: Proteins interact with one another in chain reactions or cascades (similar to blood clotting system) Two possible pathways: 1. Classical pathway - Most rapid and effective complement activation method• Complement proteins attach to antibody molecules already bound to a pathogen, Attached protein activates and initiates cascade to activate and attach other complement proteins 2. Alternative pathway - Interaction triggered by exposure to foreign substances. Several complement proteins (notably properdin) interact in the plasma. Regardless of the pathway, the effects are the same.A biochemical attack that results in pore formation (destruction), histamine release (which triggers inflammation) and improved phagocytosis (destruction).

NK Cells & Cancer

Some daughter cells grow and divide. When infection is the present, immunologic escape can lead to a failure to clear the infection. This is what happens in HIV and Hepatitis B - chronic infection.

List of Non-Specific Defenses

Summary of innate immunity Physical barriers - Prevent approach of and deny access to pathogens Phagocytes - Remove debris and pathogens Immune surveillance - Destroys abnormal cells Interferons - Increase resistance of cells to viral infections•Slow the spread of disease Complement system - Attacks and breaks down surfaces of cells, bacteria, and viruses, Attracts phagocytes, Stimulates inflammation Inflammation (multiple effects) - Fever, Mobilizes defenses, Accelerates repairs, Inhibits pathogens