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MICR20010 Agricultural Microbiology Dr. Tadhg Ó Cróinín MICR20010 - remaining lectures Lecture 10 – Microorganisms and Disease Lecture 11 – The Immune System Lecture 12 - Pathogenic Bacteria Lecture 13 – Pathogenic Fungi and Viruses Lecture 14 – Antibiotic Resistant Microorganisms Lecture 15 – Id...
MICR20010 Agricultural Microbiology Dr. Tadhg Ó Cróinín MICR20010 - remaining lectures Lecture 10 – Microorganisms and Disease Lecture 11 – The Immune System Lecture 12 - Pathogenic Bacteria Lecture 13 – Pathogenic Fungi and Viruses Lecture 14 – Antibiotic Resistant Microorganisms Lecture 15 – Identification of Microorganisms Lecture 16 – Microbiology in the Food Industry – The Fungi • Lecture 17 – Microbiology in the Food Industry Fermentations • Lecture 18 – The Nitrogen Cycle • • • • • • • Immune System vs Pathogens Immunity Concepts • Susceptibility: Lack of resistance to a disease • Immunity: Ability to ward off disease • Innate immunity: Defenses against any pathogen • Adaptive immunity: Immunity, resistance to a specific pathogen • Pathogens, agents that cause disease, infect a wide range of animals, including humans • The immune system recognizes foreign bodies and responds with the production of immune cells and proteins – All animals have innate immunity, a defense active immediately upon infection – Skin – Chemical secretions that trap/kill microbe • Vertebrates also have adaptive immunity/ acquired immunity Skin Innate immunity is present before any exposure to pathogens and is effective from the time of birth • It involves nonspecific responses to pathogens • Innate immunity consists of external barriers plus internal cellular and chemical defenses Microbiology an introduction Mucus membranes trap bacteria and move it away from Adaptive immunity, or acquired immunity, develops after exposure to agents such as microbes, toxins, or other foreign substances • It involves a very specific response to pathogens Immune system: Microbes and Defenses • The immune system recognizes bacteria and fungi by structures on their cell walls • Pathogens entering the mammalian body are subject to phagocytosis – Phagocytic cells recognize groups of pathogens by TLRs, Toll-like receptors Formed Elements in Blood Red Blood Cells (Corpuscles) Transport O2 and CO2 White Blood Cells: Neutrophils Phagocytosis Eosinophils Kill parasites Microbiology an introduction Formed Elements in Blood Monocytes Phagocytosis Dendritic cells Phagocytosis Natural killer cells Destroy target cells Microbiology an introduction Formed Elements in Blood T cells Cell-mediated immunity B cells Produce antibodies Platelets Blood clotting Microbiology an introduction A white blood cell engulfs a microbe, Phagocytosis • There are different types of phagocytic cells – Neutrophils engulf and destroy pathogens – Macrophages are found throughout the body – Dendritic cells stimulate development of adaptive immunity – Eosinophils discharge destructive enzymes Neutrophils Figure 43.3 Phagocytosis. Phago: From Greek, meaning eat Cyte: From Greek, meaning cell Pathogen PHAGOCYTIC CELL Vacuole Lysosome containing enzymes Extracellular killing by leukocytes Eosinophiles… natural killer cells Neutrophils… can carry out extracellular killing Natural killer lymphocytes (NK cells) • Secret toxin onto surface of viral infected cells • But can distinguish normal from infected cells via membrane proteins 2nd line of defence Neutrophils… can carry out extracellular killing..ways • • • Have enzymes that generate O2- and H2O2… converted to hypochlorite Produce nitric oxide.. Inflammation inducer Can make NETS (neutrophil extracellular traps).. Kill via immobilisation Bacterial Rod entrapped Budding yeast entraped in NETS Urban et al., Cellular microbiology (2006), 8, 1687. Figure 43.8-1 Pathogen Mast cell Splinter Macrophage Signaling molecules Capillary Neutrophil Red blood cells Figure 43.8-2 Pathogen Mast cell Splinter Macrophage Signaling molecules Capillary Neutrophil Red blood cells Movement of fluid Figure 43.8-3 Pathogen Mast cell Splinter Macrophage Signaling molecules Capillary Neutrophil Red blood cells Movement of fluid Phagocytosis Adaptive immunity receptors provide pathogen-specific recognition • The adaptive response heavily relies on two types of lymphocytes, or white blood cells • Lymphocytes that mature in the thymus above the heart are called T cells, and those that mature in bone marrow are called B cells • Antigens elicit a response from a B or T cell • Antigens are substances that can elicit a response from a B or T cell • Exposure to the pathogen activates B and T cells with antigen receptors specific for parts of that pathogen • The small accessible part of an antigen that binds to an antigen receptor is called an epitope Antigen receptors Mature B cell Mature T cell • Binding of a B cell antigen receptor to an antigen – an early step in B cell activation • This gives rise to cells that secrete a soluble form of the protein called an antibody or immunoglobulin (Ig) • Secreted antibodies are similar to B cell receptors – but lack transmembrane regions that anchor receptors in the plasma membrane Antibody Function • Antibodies do not kill pathogens; instead they mark pathogens for destruction and/or phagocytosis Opsonisation • In neutralization, antibodies bind to viral surface proteins preventing infection of a host cell • Antibodies may bind to toxins in body fluids and prevent them entering cells Figure 43.10a • B cells can express five different forms (or classes) of immunoglobulin (Ig) with similar antigen-binding specificity but different heavy chain C regions – IgD: Membrane bound – IgM: First soluble class produced – IgG: Second soluble class; most abundant – IgA and IgE: Remaining soluble classes Active and Passive Immunization • Active immunity develops naturally when memory cells form clones in response to an infection, Passive is when antibodies are directly donated. • It can also develop following immunization, also called vaccination • In immunization, a nonpathogenic form of a microbe or part of a microbe elicits an immune response to an immunological memory Figure 19.9 humans from pig “swine flu” 1 m (a) 2009 pandemic H1N1 (b) 2009 pandemic screening influenza A virus Killed 40 million, 19 (c) 1918 flu pandemic • Vaccines are harmless derivatives of pathogenic microbes that stimulate the immune system to mount defenses against the harmful pathogen • Vaccines can prevent certain viral illnesses Measles in the United States, 1960–2007 Microbiology an introduction Clinical Focus, p. 505 Vaccine hesitancy and effectiveness A recent challenge A brief History Success?… Next on MICR20010 Pathogenic Bacteria Dr. Tadhg Ó Cróinín
