The Human Immune System LECTURE 1 PDF

The Human Immune System Video  What is the immune system? The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles It includes all parts of the body that help in the recognition and destruction of foreign materials. eg White blood cells,...

The Human Immune System Video  What is the immune system? The body’s defense against disease causing organisms, malfunctioning cells, and foreign particles It includes all parts of the body that help in the recognition and destruction of foreign materials. eg White blood cells, phagocytes and lymphocytes, bone marrow, lymph nodes, tonsils, thymus, and the spleen are all part of the immune system.  The First Line of Defense - Anatomical barriers - Skin - Mucus membranes - GU - GI - Respiratory tracts - Physiologic barriers - pH - Fever - Enzymes - Granzymes - Lysozymes - Complement system  The Second Line of Defense ~White Blood Cells~ - If invaders actually get within the body, then your white blood cells (WBCs) begin their attack - WBCs normally circulate throughout the blood, but will enter the body’s tissues if invaders are detected Video  White Blood Cells ~Phagocytes~ These white blood cells are responsible for eating foreign particles by engulfing them Once engulfed, the phagocyte breaks the foreign particles apart in organelles called ________ Lysosomes Where could invaders hide from phagocytes?  The Second Line of Defense ~Interferon~ - Virus-infected body cells release interferon when an invasion occurs - Interferon – chemical that interferes with the ability to viruses to attack other body cells  NK cells “natural killer” cells, recognize infected human cells and cancer cells attack these infected cells, quickly kill them, and then continue to search for more cells to kill  The Second Line of Defense ~The Inflammatory Response~ - Injured body cells release chemicals called histamines, which begin inflammatory response - Capillaries dilate - Pyrogens released, reach hypothalamus, and temperature rises - Pain receptors activate - WBCs flock to infected area  Two Divisions of the Immune System - Innate - Inborn, non specific, poor memory - Adaptive - Acquired (due to exposure) Specific, - Good memory, self limiting - Humoral (B- cells- bacteria, protozoa), cell mediated (T cells – Viruses, Cancer cells) Cells of the Immune system  Organs of the immune system Primary lymphoid organs – Where the Immune cells are Produced and mature – Bone marrow , thymus Secondary Lymphoid organs – Where the immune cells Function – lymph node , spleen  Bone marrow Site of Hematopoiesis – Production of naïve B and T cells – Other blood cell types – phagocytes, erythrocytes, platelets etc – Site of maturation of B cells  Thymus Bilobed More prominent in younger children Derivative of the Third pharyngeal arch Site of maturation of T cells – Naïve T cells become Helper T cells, Cytotoxic T cells Digeorge syndrome: congenital absence of thymus – Susceptibility to what kind of infection? Immune response - Non specific Anatomical barriers – Skin prevents growth of bacteria (low pH) – Prevent invasion of pathogens except when breeched – Mucosal membranes can be ciliated (e.g respiratory tract) to facilitate expulsion of foreign particles Secretion of large amount of fluid in diarrhea to get rid of pathogen Low pH of stomach kill most bacteria – Fever has bacteriostatic function, also inactivates enzymes, some of which are need for bacteria growth Specific immune response  Humoral Immunity B Lymphocytes Produced in bone marrow – Make antibodies (immunoglobulins) once activated to plasma cells – Memory B cells provide a quicker response t the same pathogen on second exposure  Antibodies Protein molecules produced by B-cells Specific shapes allow binding to specific molecules (antigens) Allow body to respond defensively to presence of specific potential threats  Antibody Types IgG IgM IgA IgD IgE  IgM First antibody to be made in an acute infection Changed to other Ig classes by class switching main role is in the complement system  IgG Most common antibody type Only antibody that crosses placenta Prime mediator of secondary immune response Principal defender against bacteria, viruses, and toxins Roles: antibody dependent cell mediated killing, opsonization, neutralization, less effective in complement activation  IgA Secretory Ig Found in saliva, and other secretory mucus membranes e.g. GIT, respiratory tract Main Ab in breast milk – Colostrum Role: prevents adherence of pathogens to mucosa, passive immunity in newborn  Cell-Mediated Immunity T Lymphocytes – Originate in bone marrow – Altered by passage through thymus – Responsible for mediation of cellular immunity  T Lymphocyte Types Helper cells (T4 cells) Cytotoxic cells (Killer T cells) Suppressor cells Memory cells  Helper T-Cells Master “on-switch” of immune system Recognize antigens Secrete lymphokines that activate all other immune system cells Stimulate B-cells to begin antibody production  Cytotoxic (Killer) T-Cells Respond to presence of antigens and lymphokines produced by T-4 cells Seek out, bind to, and destroy: – Cells infected by viruses – Some tumor cells – Cells of tissue transplants Can deliver lethal hits on multiple cells in sequence  Suppressor T-Cells Produce lymphokines that inhibit proliferation of B and T cells Downregulate or dampen immune response  Memory T-Cells Have previously encountered specific antigens Respond in enhanced fashion on subsequent exposures Induce secondary immune response  What is immunity? - Resistance to a disease causing organism or harmful substance Two classifications – Natural vs. Acquired – Active vs. Passive  Active Immunity - You produce the antibodies - Your body has been exposed to the antigen in the past either through: - Exposure to the actual disease causing antigen – You fought it, you won, you remember it - Planned exposure to a form of the antigen that has been killed or weakened – You detected it, eliminated it, and remember it What is this second type of exposure called?  Vaccine Antigens are deliberately introduced into the immune system to produce immunity Because the bacteria has been killed or weakened, minimal symptoms occur Have eradicated or severely limited several diseases from the face of the Earth, such as polio and smallpox  How long does active immunity last? It depends on the antigen Some disease-causing bacteria multiply into new forms that our body doesn’t recognize, requiring annual vaccinations, like the flu shot Booster shot - reminds the immune system of the antigen Others last for a lifetime, such as chicken pox  Passive Immunity You don’t produce the antibodies – A mother will pass immunities on to her baby during pregnancy - through what organ? Placenta – These antibodies will protect the baby for a short period of time following birth while its immune system develops. What endocrine gland is Why doesn’t the mother just responsible for this? Thymus pass on the WBCs that – Lasts until antibodies die “remember” the antigens? Disorders of the immune system Phagocytic deficiencies Complement deficiencies T cell deficiencies B cell deficiencies Combined B and T cell deficiencies Others: Hypersensitivity disorders, autoimmune disorders