Immunology - Innate Immunity Notes

Immunology studies the immune system and its components, trying to understand how our bodies defend against pathogens.
The course is challenging due to the breadth of terminology and concepts involved.

Innate Immunity: The body's first line of defense that includes physical, chemical, and genetic barriers as well as immune response mechanisms (phagocytosis, inflammation).

Physical Barriers: Skin and mucous membranes that prevent pathogen entry.
Chemical Barriers: pH and temperature of the skin, perspiration, and antimicrobial peptides that deter microbe growth.
Genetic Barriers: Genetic traits that may make individuals more resistant to certain infections.

Inflammation: Rapid response triggered when pathogens bypass the first line by increasing blood flow and immune cell recruitment.
Phagocytosis: A type of cellular immune response where phagocytes like neutrophils and macrophages engulf and digest pathogens.
Cytokines: Signaling proteins that mediate and regulate immunity, inflammation, and hematopoiesis.

Granulocytes: Includes neutrophils, eosinophils, and basophils that have granules filled with enzymes.
- Neutrophils: Most abundant; first responders that trap and kill pathogens.
- Eosinophils: Active in allergic reactions and defend against parasites.
- Basophils: Release histamine and play a role in inflammatory reactions.
Agranulocytes: Includes lymphocytes (B and T cells) and monocytes.
- Monocytes: Differentiate into macrophages and dendritic cells that act as antigen-presenting cells (APCs).
- Lymphocytes: Involved in adaptive immunity; B-cells produce antibodies, T-cells destroy infected cells.

A series of proteins that enhance the ability of antibodies and phagocytic cells to clear pathogens.
Functions include opsonization (marking cells for destruction), inflammation, and forming the membrane attack complex (MAC) to lyse pathogens.

Classical Pathway: Triggered by antibodies bound to an antigen.
Alternative Pathway: Activated by pathogen surfaces directly.
Lectin Pathway: Triggered by mannose-binding lectin binding to specific sugars on pathogens.

Chemotaxis: Movement of phagocytes towards the site of infection.
Adherence: Binding of the phagocyte to the pathogen.
Ingestion: Engulfing the pathogen in a phagosome.
Digestion: Fusion of the phagosome with lysosomes to form a phagolysosome where pathogen destruction occurs.
Discharge: Release of indigestible material.

Redness (rubor): Vasodilation increases blood flow.
Swelling (tumor): Fluid accumulation due to increased permeability of blood vessels.
Heat (calor): Increased blood flow raises temperature in the affected area.
Pain (dolor): Caused by the release of inflammatory mediators.

Diagnostic Tests: Complete Blood Count (CBC) helps analyze immune response.
Vaccination: Stimulates acquired immunity, highlighting the interplay of innate and adaptive immunity.

Understanding innate immunity is crucial as it establishes the foundation for adaptive immune responses.
Both systems work closely together to ensure effective protection against pathogens, enabling proper immune function and health maintenance.