Immunology - Adaptive & Innate Immunity

Innate Immunity: Rapid (hours), non-specific, lacks immunological memory, and uses uniform responses.
Adaptive Immunity: Slow initial response (days/weeks), highly specific, develops lifelong memory, and improves upon repeated exposure.

Includes physical barriers (skin, mucous membranes, tight junctions) and chemical defenses (stomach acid, lysozyme in tears/saliva, defensins, and commensal flora) that prevent pathogen entry.

Innate immune cells use PRRs (e.g., Toll-Like Receptors / TLRs) to detect conserved evolutionary structures on pathogens called PAMPs (Pathogen-Associated Molecular Patterns, like bacterial LPS or viral dsRNA).

Innate lymphocytes that destroy virally-infected cells and tumor cells without prior sensitization. They induce apoptosis using perforin and granzymes when detecting downregulation of MHC Class I ("missing-self" hypothesis).

Characterized by rubor (redness), calor (heat), tumor (swelling), dolor (pain), and functio laesa (loss of function). Mediated by histamine, prostaglandins, and bradykinin driving vasodilation and increased vascular permeability.

1. Classical Pathway: Triggered by antigen-antibody complexes.
2. Lectin Pathway: Triggered by mannose-binding lectin binding pathogen sugars.
3. Alternative Pathway: Triggered directly on foreign cell surface molecules (spontaneous C3 hydrolysis).