IMMUNOLOGY BASICS Lactation Biology Animal Science

IMMUNOLOGY BASICS Lactation Biology Animal Science 337 Leo Timms Iowa State University MEANS OF AQUIRING IMMUNITY 1. ACTIVE: make own antibody chance encounter w/Ag a) natural pregnancy vaccination b) artificial introduce Ag via trt. MEANS OF AQUIRING IMMUNITY 2. PASSIVE: transfer preformed antibody a) natural : mother to fetus (6 mo protection) placental vs. colostral b) artificial: immune therapy Type of immune response • Innate • defense we are born with – phagocytic cells – complement proteins – anatomical * – physiological * • Adaptive/acquired • defense that develops with exposure/time – serum antibodies – T cells (CMI) * 1st line of defense!!! Mechanisms of immunity: • Cellular • Humoral – cells responsible – antibodies (in for protection serum) are responsible for – lymphocytes protection – phagocytes Two Arms of The Immune System Innate Immunity Phagocytes Adaptive Immunity Lymphocytes Neutrophils pathogens Macrophages Antigen presentation T lymphocytes B lymphocytes pathogens Antigen presentation TH1 Cytokines chemokines TH1 Cytokines TH1 or TH2 Cytokines Cytotoxicity Antibodies © Jeanne L. Burton, Michigan State University Cells of the Immune System Myeloid-lineage cells of the innate immune system PMN M Tissue macrophage Circulating neutrophil B TH TC B cell Helper T cell (TH) Cytotoxic T cell (TC ) Lymphoid-lineage cells of the adaptive immune system © Jeanne L. Burton, Michigan State University • large cell (10-25 um dia) • main purpose: phagocytosis / kill • act non specifically • “chemotactic” capability • potent phagocytosis when activated by T lymphocytes (lymphokines) • Express Ag on surface to T / B cells • multilobulated nucleus • lysosomal granules • phagocytosis and kill • 1st white blood cell to infection site • die and release contents • irritate surrounding tissue / recruit cells • Phago. improved by opsonization with Ig Macrophages and neutrophils are needed to kill extracellular bacteria, such as those the infect the mammary glands of dairy cows Tissue macrophage Blood IL-1, IL-6, IL-8,TNF-a M PMN TNF-a Circulating neutrophil PMN IFN-g No memory M or PMN cells develop Extracellular bacteria Inflammatory neutrophil © Jeanne L. Burton, Michigan State University Infected Gland Inflammation: part of innate immunity • poor at phagocytosis • granules contain histamine / serotonin • vasodilators / permeability factors • requires binding of 2 IgE for release lymphocytes • small (5 – 15 um) • No lysosomes : all “brain” until activated • distinguish self from non self • specific : recognize specific antigens • MEMORY** • need presentation of Ag by macrophage • interactions - antigen - macrophage - T cell (Th) - B cell - cytokines cytokines • interactions - antigen - macrophage - T cell (Th) - cytokines T helper (Th) T suppressor T killer others CYTOKINES / LYMPHOKINES Small polypeptide messengers • very powerful in low doses • multiple uses • hormones Interleukins Interferon: viral Colony Stimulating factors: GCFS Tumor Necrosis Factor (TNF) inflammation / cell movement / traffic • 1. 2. 3. 4. OTHER IMMUNE FACTORS • Complement: 9 specific serum proteins - interaction of components provide numerous biological events • Lactoferrin: Iron binding protein *** competes with bacteria for iron • Lactoperoxidase ( LP/ SCN- / H2o2 syst.) ** antioxidant / oxygen radicals HUMORAL IMMUNITY (Ab or AMI) • Antigen + Macrophage + T cell + B cell cytokines • Antibodies or Immunoglobulins • SPECIFICITY! • MEMORY • (immunity: short, long, or no term) Antibodies are produced by antigen-activated B lymphocytes and, in cattle, come in six isotypes Fab = antigen binding = Fab variable region IgM (m) IgG1 (g1) IgG2 (g2) IgG3 (g3) IgA (a) IgE (e) L L Fc = biological function H H constant region (Fc-m) L = light chain H + heavy chain © Jeanne L. Burton, Michigan State University Functions • Variable region (Fab) bind specifically-neutralize, ppt or agglutinate **** antigen binding region • Constant region (Fc) – - activate effector cells or complement - opsonin end Antibody Isotypes-5 IgG: IgG1 IgG2 • Principle Ab in serum • 14 – 18 mg / ml • IgG1: 11 mg/ml • IgG2: 7 mg/ml • fixes complement • late response to Ag IgG2 10 opsonin for phagocytosis IgG1 • selective transfer (colostrum) • fetal / neonatal defense • toxin inactivation • principal milk / colostrum Ig (farm species) Neutralization • As single molecule of toxin can kill • Ab must diffuse rapidly, bind with high affinity Neutralize virus • Virus binds to cell receptor • eg: sialic acid on glycoproteins of RBC or epithelial cells Opsonization • Free IgG binds Fc receptors with low affinity • IgG bound to Ag, binds to Fc receptors with high affinity • Cross-linking receptors sends signal IgM • largest Ig • pentamer • serum (1-3 mg/ml) • fixes complement • 1st Ig produced to Ag challenge! • Binds to mast cells basophils • ACTIVATION • RELEASE OF - histamine - serotonin IgE The various Fc portions of antibody molecules have very different biological functions, including pathogen blocking, complement fixation, toxin neutralization, and opsonization of bacteria for enhanced phagocytosis by neutrophils and macrophages IgM = blocking & complement fixation IgG1 = endotoxin IgG2 = opsonization neutralization & & neutrophil complement fixation phagocytosis serum complement © Jeanne L. Burton, Michigan State University In cattle, IgG2 antibodies leak from blood into infected mammary glands and act as the key opsonin to help neutrophils target and clear mastitis-causing bacteria Blood Flow Neutrophil Neutrophils Edema Blood Vessel Wall Cytokines M M IgG2 Fc Receptor Opsonizing IgG2 Bacterium Milk Burton and Erskine, 2003 Neutrophil Phagocytosing IgG2 Opsonized Bacteria • 3 different forms in serum • different form in secretion ( secretory piece) • serum: 1-3 mg/ ml • activates complement: serum (yes) milk (no) IgA Secretory piece • local immunity and secretions • prevents bacterial adherence • maternal milk: very important • primary Ig in colostrum (humans)! Transcytosis -source of secretory component?