BIOL 1003: Immunity Overview

Innate and Adaptive Immunity

• Innate Immunity: The body's first line of defense, consisting of physical and biochemical barriers.
• Adaptive Immunity: Acquired immunity involving B and T cells, providing 'memory' responses as a third line of defense.

Physical and Chemical Barriers

• Physical Barriers:
  • Skin covers approximately 2 m².
  • Epithelial linings of gastrointestinal, genitourinary, and respiratory tracts span around 32 m².
  • Includes tight junctions, sloughing off of cells, mucus, and cilia.
• Chemical Barriers:
  • Secretion of saliva, tears, earwax, sweat, and mucus contributes to protection.
  • Antimicrobial peptides, including cathelicidins and collectins, play a role.
  • pH levels: Skin (3-5), Stomach (1.5-3.5).

Inflammation: Response Mechanism

• Inflammation is the host response to vascular tissue damage, featuring redness, heat, swelling, pain, and loss of function.
• Goals include limiting tissue damage, destroying microorganisms, initiating adaptive immune responses, and clearing debris.
• Acute Inflammatory Response: Involves cellular injury, activation of plasma systems, and release of autocoids.

Plasma Protein Systems

• Systems contain inactive enzymes (proenzymes) that sequentially activate to combat infections.
• The Complement System activates both innate and adaptive immunity, destroying pathogens and enhancing the inflammatory response through pathways like classical, lectin, and alternative.
• Coagulation System creates a fibrin meshwork to trap pathogens and aid in repair.
• The Kinin System activates inflammatory cells and elevates vascular permeability.

Cellular Mediators of Inflammation

• White Blood Cells (WBC): Includes granulocytes, platelets, monocytes (macrophages, dendritic), and lymphocytes (T, B, NK).
• Mast Cells: Located close to blood vessels; release histamine and chemotactic factors upon degranulation.
• Cytokines are critical in signaling and modulating immune responses, classified into interleukins, interferons, and tumor necrosis factor-alpha (TNF-α).

Cytokines

• Interleukins (IL): Produced primarily by macrophages and lymphocytes, facilitating chemotaxis and regulating immune activity.
• Interferons (IFN): Protect against viral infections; types include IFN-alpha, IFN-beta, and IFN-gamma.
• Tumor Necrosis Factor-alpha (TNF-α): Induces fever, increases inflammatory proteins, and can cause muscle wasting.
• Chemokines: Attract leukocytes to inflammation sites.

Phagocytosis

• A cellular process that engulfs and disposes of foreign material, carried out in two phases:
  • Extravasation: Involves margination and diapedesis.
  • Phagocytosis: Involves adherence, engulfment, phagosome formation, and fusion with lysosomes.

Acute vs. Chronic Inflammation

• Acute Inflammation: Self-limiting and characterized by heat, swelling, redness, and pain. Leads to exudative fluid production.
• Chronic Inflammation: Lasting over two weeks, often resulting from an unsuccessful acute response, high lipid content microbes, or toxins.

Exudative Fluids

• Serous Exudate: Watery fluid indicating early inflammation.
• Fibrinous Exudate: Thick, clotted fluid reflecting advanced inflammation.
• Hemorrhagic Exudate: Contains blood, indicating bleeding.
• Purulent Exudate: Pus indicating bacterial infections.

Systemic Acute Inflammation

• Fever: Triggered by pyrogens acting on the hypothalamus.
• Leukocytosis: Increased WBC count, with a 'left shift' indicating more immature neutrophils.
• Acute Phase Reactants: Elevated plasma proteins such as C-reactive protein and fibrinogen, associated with the inflammatory response.

Chronic Inflammation Characteristics

• Dense lymphocyte and macrophage infiltration, granuloma formation, epithelioid and giant cell formation.