Immunity to microbes
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Transcript of Immunity to microbes
Immunity to Microbes
Fadel Muhammad Garishah
Infection and Immunity
Faculty of Medicine Diponegoro University
General features
• Defense against microbes via innate and adaptive immunity
• Responds in distinct and specialized ways to different types of microbes
• survival and pathogenicity of microbes influenced by the ability of the microbes to evade or resist the immunity
• tissue injury and disease may be caused by the host response to the microbe and its products rather than by the microbe itself.
Extracellular Pathogenic Bacteria
Extracellular bacteria Human Diseases Pathogenicity
Staphylococcus aureus Skin/soft tissue infection, lung abscess, Systemic: toxic shock syndrome, food poisoning
Enterotoxin superantigeninduced
Streptococcus pyogenes Group A
Pharyngitis, Skin impetigo;Cellulitis, Scarlet fever (rheumatic fever)
Streptolysin-0
Streptococcus pneumonia
Pneumonia, Pneumococcusmeningitis
Pneumolysin, Capsule
Escherichia coli UTI, Genteritis, Septic shock LPS Endotoxin
Vibrio cholerae Diarrhea cholerae Cholera toxin (cAMPincreases)
Clostridium tetani Tetanus Tetanus toxin
Neisseria meningitidis Meningococcus meningitis Endotoxin
Corynebacteriumdiphtheriae
Diphtheria Diphtheria toxin
The extracellular bacteria
• Extracellular bacteria defined as the bacteria that capable to replicate outside the host cells, e.g. in blood, connective tissue, airway/gastrointestinal tract
• The bacteria may either 1) induce inflammation or 2) produce toxins that destruct the body tissue
• E.g. of toxin: Endotoxin of gram-negative or lipopolysaccharide (LPS).
Innate immunity to extracellular bacteria
• Principles: complement activation, phagocytosis and inflammatory response.
• Complement activation
• Activation of phagocytes and inflammatory response
Adaptive immunity to extracellular bacteria
• Humoral immunity: block infection, eliminate microbes and neutralize toxins
• CD4+ produces cytokines that induce local inflammation and activate phagocytic function and microbicidal activities of Macrophages and Neutrophiles
Extracellular bacteria evasion
• A mechanism used by bacteria to evade humoral immunity.
• Genetic variation of surface antigen (E. coli, N. gonorrhoeae, S. typhimurium)
• Resistance to phagocytes (Pneumococcus)
• Destruction to ROS (Catalase producing Staphylococci)
Intracellular bacteria
• A characteristic of facultative intracellular bacteria is their ability to survive even replicate within phagocytes.
• Requires cell-mediated immunity
Intracellular bacteriaMicrobe Human Diseases Pathogenicity
Mycobacteria species Tuberculosis, Leprosy Macrophage activation,granulomatous inflammation, tissue destruction
Listeria monocytogenes Listeriosis Listeriolysin damages cell membrane
Legionella pneumophila Legionnaires’ disease Cytotoxin lyses cells
Innate and Adaptive Immunity
• The innate immune response to intracellular bacteria consists mainly of phagocytes and NK (natural killer) cells.
• The major adaptive-protective immune response against intracellular bacteria is cell-mediated immunity
• The macrophage activation in response to intracellular microbes is capable of causing tissue injury
Figure 15-5 Naive CD4+ T lymphocytes may differentiate into TH1 cells, which activatephagocytes to kill ingested microbes, and TH2 cells, which inhibit macrophage activation.The balance between these two subsets may influence the outcome of infections, asillustrated by Leishmania infection in mice and leprosy in humans.
Mechanisms of Immune Evasion by Bacteria
• Inhibition of phagolysosome formation (Mycobacterium tuberculosis, Legionella pneumophila)
• Inactivating reactive oxygen and nitrogen intermediates Mycobacterium leprae(phenolic glycolipid)
• Disruption of phagosome membrane, escape into cytoplasm Listeria monocytogenes(hemolysin protein)