Overview of Immune System
An immune response, coordinated by the immune system, aims to eliminate antigens through antibody generation. |
The immune system consists of innate and adaptive branches with common features: Recognition of diverse pathogens Elimination of identified invaders Discrimination between self and foreign antigens |
Innate immunity is non-specific and ancient, found in all eukaryotic organisms. |
Adaptive immunity, unique to vertebrates, matures over time, tailors responses, and exhibits memory. |
Microbiota play a crucial role in shaping and regulating immune responses. |
Fever
Abnormally high body temperature induced by pyrogens. |
Enhances antiviral effects, phagocyte efficiency, leukocyte production, limits pathogen growth, and promotes tissue repair. |
Low-grade fever (37.5°C to 38.3°C) is protective; high fever (40.5°C) is life-threatening |
Blood Components and Leukocytes
Blood Composition - Erythrocytes transport oxygen, platelets stem blood loss, leukocytes are crucial for the immune system. Leukocytes: granulocytes (visible granules) and agranulocytes (lack granules). |
Leukocyte Activation Activated leukocytes release molecules for diverse functions. These molecules have diverse functions, including recruiting other leukocytes, restricting pathogen growth, triggering fever, and stimulating inflammation |
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Microbial Impact on Immunity
Changes in normal microbiota can confuse the immune system, linked to allergies and autoimmune diseases. |
Hygiene Hypothesis suggests reduced microbial diversity hinders immune responses. |
Mechanical and Chemical Barriers
Mechanical barriers (e.g., skin, tears, urine) hinder pathogen entry. Chemical barriers combat invaders (e.g., lysozyme, stomach acidity) |
Antimicrobial peptides (AMPs) like defensins target pathogens by inserting into cell membranes. |
The Plague
Signs and Symptoms: Fever, chills, weakness, abdominal pain, diarrhea, vomiting, bleeding, shock, tissue death. |
Plague Doctors Distinctive attire: beaked mask, cane, long coat, gloves, hat. Protection against bacteria-laden secretions and aerosol droplets. |
Mortality Historical impact with devastating outbreaks (Plague of Justinian, Black Plague, Great Plague of London, Third Pandemic). |
Types of Leukocytes
Neutrophils: Most abundant, engage in phagocytosis. Eosinophils: Combat parasitic infections and allergic responses. Basophils: Involved in allergic responses and combat parasitic infections. Mast Cells: Release histamine, contribute to allergic responses and parasitic defense. Monocytes: Mature into macrophages, involved in chronic infections, inflammation, autoimmune disorders, and cancers. Macrophages: Highly phagocytic, destroy a wide range of pathogens, serve as antigen-presenting cells. |
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Blood and Lymphatic System
Blood delivers plasma to tissues, forming interstitial fluid |
Lymphatic system collects and filters lymph (fluid), screening for pathogens in lymph nodes |
Primary lymphoid tissues (thymus, bone marrow) produce and mature leukocytes. |
Secondary lymphoid tissues (nodes, spleen, MALT) filter lymph |
Yersinia pestis and Immune System
Infection Encounter Yersinia pestis faces non-specific immune defenses and leukocytes. |
Evasion Strategies Counteracting defenses, reducing phagocytosis, producing a protective capsule, using injectosomes. Plasmids generate proteins suppressing lymphocyte chemotaxis. |
Immune Evasion Strategies of Yersinia pestis
Subverts macrophages, impairs inflammatory response, targets natural killer cells, produces proteases. |
Natural Killer Cells
Abundant in the liver, provide innate protection against viruses, bacteria, parasites, and tumor cells. |
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Treatment and Mortality of the Plague
Intravenous antibiotics (gentamicin, ciprofloxacin) recommended for Yersinia pestis. |
Inflammatory Response
Inflammation is essential for innate immunity and healing. |
Three phases: vascular changes, leukocyte recruitment, resolution. |
Chronic inflammation exacerbates tissue injury and promotes diseases |
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