Ch 43: The Immune System Nicole Ferrante Ben Fewkes Jenny Menendez

Innate immunity: – first major kind of defense – effective from time of birth – non-specific Acquired (adaptive) immunity: – Second major kind of defense – Exposure after induced agents – Highly specific

Innate Immunity External Defense – Skin – Mucous Membrane – Secretions Lysozyme- a secretion from skin and mucous membranes

Innate Immunity Cont. Internal Defense – Phagocytosis Bind via surface receptors not on human blood cells Phagocyte engulfs microbe…forming a vacuole with a lysosome Destroyed by… – Nitric oxide and other toxic forms of oxygen in lysosome poison microbes – Lysozyme and other enzymes degrade microbial components

Internal Defense Phagocytic cells – Neutrophils Enter infected tissues, engulfing/destroying microbe Self- destruct in phagocytosis and average life span is a few days – Macrophages (“Big eaters”) Large, long-lives, develop into monovytes 5% of curculating White Blood Cells Circulate in blood stream fcor several hours Some migrate throughout the body others reside permanently in organs – Eosinophils Low phagocytic activity Crucial to defense against multicellular parasites Don’t engulf they discharge destructive enzymes that damage the invader – Dendritic Can ingest microbes Stimulate the development of acquired immunity

Inflammatory Response – Histamine: active chemicals in Inflammatory Response Trigger dilation and increase permeability of capillaries Results in promoting blood flow to injured site – Mast Cells Connective tissues – Natural Killer Cells Patrol body and attack virus-infected cells and cancer cells – Apoptosis: programmed cell death

Acquired Immunity – Antigen: any foreign molecule that is specifically recognized by lymphocytes and elicits a response from them Large molecules, either proteins or polysaccharides – Epitope: small, accessible portion of an anitgen Induce a response from lymphocytes

Antigen Recognition B Cell Receptors – “y” shaped – 4 polypeptide chains 2 heavy chains, 2 light chains T Cell Receptors: consists of 2 different polypeptide chains (α&β) – Antigen presentation: MHC molecule binds with a fragment of protein within the cell and brings it to the cell surface – Class I MHC Molecules: Bind peptides derived from foreign antigens that have been synthesized in the cell Represented in the subgroup of T cells: Cytotoxic T Cells – Class II MHC Molecules Dendriticcells, macrophages and Bcells known as anitgen-presenting cells Bind peptides derived from foreign materials that have been internalized and fragmented through phagocytosis or endocytosis

Humoral vs cell-mediated Humoral immune response: involves the activation and clonal selection of B cells, resulting in production of secreted antibodies that circulate in the blood and lymph Cell-mediated immune response: activation and clonal selection of cytotoxic T cells, which directly destroy certain target cells

T Cells Helper T cell: stimulates the activation of nearby B cells and cytotoxic T cells CD4: Helps bring the Class 2 MHC molecules with the Helper T CD8: Enhances interaction between a target cell and a cytotoxic T cell

Active and Passive Immunization Active Immunity: Depend on action of person’s own lymphcyte and the resulting memory cells specific for the invading pathogens Immunization/Vaccination Passive Immunity: doesn’t depend on person’s lymphocytes – Provides immediate protection

Blood Groups

Autoimmune Diseases Immune system loses tolerance for self and turns against certain molecules of the body. Example: – Systematic lupus erythematosus (lupus), generates antibodies against the bodies natural defense (histones and DNA released by the normal breakdown.) – Rheumatoid arthritis, damage and painful inflammation of cartilage and bone of joints. – Insulin-dependent diabetes mellitus, insulin-producing B cells of the pancreas are targets of autoimmune cytotoxic T cell – Multiple Sclerosis, T cells infiltrate the central nervous system and destroy the mycelin sheath that surrounds some neurons

Immunodeficiency Diseases Inborn (primary): result from defects in the development of various immune system cells or defects in the production of specific proteins – Severe combined immunodeficiency: both humoral and cell-mediated branches of acquired immunity fail to function Gene Therapy Bone Marrow Transplants Acquired (secondary): an immune dysfunction that develops later in life can be caused by exposure to a number of agents. – Acquired ImmunoDeficiency Syndrome (AIDS) More chances for infectious diseases – HIV (Human Immunodeficiency Virus), retrovirus that causes AIDS