Immune System Organs, Cells and Molecules that Protect Against Disease

Lymphocytes called T cells Lymphocytes called B cells Chemical BarriersResident Bacteria Protective Proteins Complement and Interferon Response that surrounds and engulfs invaders

Organs and Vessels of the Lymphatic System Red bone marrow: production of B and T lymphocytes, maturation of B cells Thymus: maturation of T cells Spleen: Lymphocytes and macrophages react to pathogens in blood Lymphatic Vessel: carries lymph, a fluid containing lymphocytes and pathogens Tonsil: Lymphocytes react to pathogens entering through nose and mouth Lymph nodes: Lymphocytes and macrophages react to pathogens in lymph

B Cell Selection, Activation and Differentiation Antigen: Protein on surface of invader, recognized as foreign =Antibody: Protein made by B cells to mark invader for destruction Plasma Cell secretes antibody into blood Memory B cell is activated in a later infection by the same invader

Antibody Structure  Antibody has 2 heavy chains and 2 light chains.  Each chain has variable (V) and constant (C) region.  Variable regions bind to antigen.  Constant regions bind to cells or other antibodies. V V C CC V V C antigen C = constant V = variable shape of antigen fits shape of binding site antigen-binding sites antigen binds to binding site light chain heavy chain

T Cell Selection, Activation and Differentiation =T cell receptor: Binds to antigen presented by macrophage Cytotoxic T cell: Kills cells infected with the invader Memory T cell: Responds in another infection by the same invader

Action of Cytotoxic T Cells Two Products: –Perforin: protein that is inserted into target cell membrane, creating openings –Granzymes: enzymes that stimulate apoptosis cytotoxic T cell vesicle perforin Cytotoxic T cell granzyme target cell (virus-infected or cancer cell) Perforin forms hole in target cell. Granzymes enter through the hole and cause target cell to undergo apoptosis. Target cell

Communication Among Cells 1. Macrophage engulfs invader 2. Macrophage displays “processed” antigen 5. Macrophage releases cytokines to activate Helper T cell 4. Helper T Cell binds to Macrophage 3. Invader binds to B cell that carries antibody matching the antigen 6. Activated Helper T cell stimulates division of selected B cell 7. Dividing B cell gives rise to memory B cells and plasma cells

Properties of the Immune Response A.Specificity: A.Specificity: Unique response against each each invader B. Memory: Increased response at next invasion C. Discrimination: Ability to distinguish “self” from “non-self”

Memory Cells and the Immune Response

Humoral and Cellular Immunity Humoral(Antibody-mediated)Cellular (T-cell mediated) Hay fever Reaction to poison ivy Transfusion reactions Tuberculin Test Rh disease Reaction to bee stings Immunization Graft (organ) rejection Viral and Bacterial infections Cancer Prevention

Diseases of the Immune System A.Inherited A.Inherited Immune Deficiencies eg. SCID: Severe Combined Immune Deficiency B. AIDS: Acquired Immune Deficiency Syndrome HIV infects Helper T Cells C. Autoimmune diseases 1. Myasthenia Gravis 2. Rheumatoid arthritis 3. Lupus 4. Multiple Sclerosis D. Allergies

HIV Glycoproteins Glycoproteins Envelope (lipid bilayer) Envelope (lipid bilayer) Protein Coat Protein Coat Core Proteins Core Proteins Reverse Transcriptase Reverse Transcriptase Viral RNA in protein coat Viral RNA in protein coat

HIV Infection Helper T Cell (green) Helper T Cell (green) Recently emerged HIV particles (red) Recently emerged HIV particles (red) Emerging HIV particles Emerging HIV particles Envelope acquired from helper T cell Envelope acquired from helper T cell

Allergic Reactions Pollen grains enter respiratory tract Pollen binds to allergy antibody Causes release of histamine, which causes symptoms Mast Cell “Allergy” plasma cell releases “allergy” antibodies (IgE) Binding site for “allergy” antibodies Histamine vesicle