Lymphatic System & Immunity

Transcription

1 Lymphatic System & Immunity Arteriole Venule Tissue Blood Lymph cells capilla capillaries ries Lymphatic System -closely related to cardiovascular system -conducting system that carries fluid from extracellular spaces to blood -no heart or pumping apparatus -circulation is relied on skeletal muscle movements -'milking' action (slowly moving system) -suction of pressure gradients always towards thoracic cavity -continuous process -system of blind-ending tubes -lymphatic vessels -thin walls & valves -similar to veins & capillaries -no arteries or arterioles -one-way flow -lymph capillaries -afferent lymph vessels -lymph nodes -efferent lymph vessels -right & left lymphatic ducts (thoracic duct) -right & left subclavian veins - when extracellular fluid enters lymphatic vessels, it is called lymph

2 Lymph -contains many of the same components of blood plasma; 2-3 liters of lymph/day returns to blood circulation Lymph nodes -aggregation of cells that produce lymphocytes -lined w/phagocytic cells (macrophages & lymphocytes) Lymphatic System Overview

3 Immunity & Immune system Overall functions: -defend the body from infection -help maintain homeostasis -2 general types of immunity 1) Nonspecific defense immunity 2) Specific immunity Bozeman Immune System: NSI/SI

4 Nonspecific defense (innate) immunity -response to any tissue damage -response to any presence of foreign substance -inflammatory response -release of phagocytic cells -tissue fluid ph lowers -damage cells release lysosomes

5 Steps involved w/nonspecific defense mechanisms 1) tissue injury & microorganism invasion 2) vasodilation of blood vessels near wound 3) increase permeability of blood vessel walls 4) phagocytosis of microorganisms 5) tissue debris tissue repair NSI Rap

6 Specific (Adaptive) immune response 3 Characteristics of Specific Immune Response: 1) Specificity -distinguish one antigen from another 2) Heterogeneity/Systemic -many different antibodies respond to same antigen -Not restricted to initial site of infection/invasion 3) Memory -recognize previous antigens

7 Histology of Specific (Adaptive) Immune System- Lymphocytes 1) B cells -antibody-mediated immunity -mature in bone marrow -produce & secrete antibodies -outer membrane receptor molecules -clonal expansion -production of memory & plasma cells -memory cells remain in lymph nodes -associated w/ humoral immunity (antibody mediated response) 2) T cells -associated w/cell-mediated immunity -mature in thymus -some T cells directly attack antigens -some T cells regulate immunity

8 Steps of the Specific (Adaptive) Immune Response 1. Threat -Foreign organism or molecule (an antigen) enters the body 2. Detection -Macrophage detects foreign organism or molecule and engulfs it 3. Alert -Macrophages present antigens to helper T cells -Macrophages are antigen-presenting cells -Helper T cells are the main switch for the adaptive immune response

9 Steps of the Specific (Adaptive) Immune Response 4. Alarm -Helper T cells activate appropriate B cells and T cells to destroy the specific antigen -When activated, these cells divide to form clones of cells designed to eliminate the specific antigen from the body -Clonal selection is critical to the adaptive immune response 5. Building specific defenses -B cells form plasma cells that secrete antibodies into the bloodstream, which bind to antigens -T cells form cytotoxic T cells that attack -Process by which immune cells increase in number is termed clonal selection SI Rap

10 Types of T cells a) Cytotoxic T cells - killer T cells' -seek out & attack antigens by releasing chemicals called perforins. They cause the target cell to burst. Cytotoxic T Cell animation

11 Types of T cells (cont.) b) Helper T cells -regulate immune response -release lymphokines, which activate macrophages -stimulates cloning & B cells (antibodies) Role of Helper T cells

12 Types of T cells (cont.) c) Memory & Suppressor T Cell -helper T cell clones -prevent B cell antibody production Latest research on memory T- cells

13 Cell-mediated immune response Steps 1-4 is the same as the adaptive Immune response 5. Building specific defenses -B cells form plasma cells that secrete antibodies into the bloodstream, which bind to antigens -T cells form cytotoxic T cells that attack -Process by which immune cells increase in number is termed clonal selection 6. Defense: the antibody-mediated response -Antibodies secreted by plasma cells are specific to the antigen and eliminate that antigen Precipitation Lysis (bursting) Attraction of phagocytes Neutralization -An effector cytotoxic T cell releases perforins, which cause holes to form in cells with the particular antigen 1 Threat Antigen Virus 2 Detection 3 Alert 4 Alarm The helper T cell stimulates a naive or memory cytotoxic T cell to begin dividing. 5 Building specific defenses The cytotoxic T cell divides and forms effector cytotoxic T cells and memory cytotoxic T cells. 6b Defense Effector cytotoxic cells cause the target cell to burst and die. In this case, the target cell is a cell infected with a virus that triggered the response. Perforin T cell membrane Target cell membrane Perforin assembling into pores 7 Continued surveillance Memory cytotoxic T cells remain and mount a quick response if the invader is encountered again. Effector cytotoxic T cell Target cell Antigen-presenting (macrophage) Cytotoxic T cell cell Helper T cell Memory cytotoxic T cell 7. Continued surveillance -Immunological memory allows for a more rapid response on subsequent exposure to the antigen Primary response -Occurs during body s first encounter with a particular antigen -Antibody concentration rises slowly Secondary response -Occurs during subsequent encounter with that antigen -Strong and swift due to the large number of memory cells programmed to respond to that particular antigen Memory cytotoxic T cells

14 Summary of the Specific (Adaptive) Immune Response