Non-specific Immunity (second line)

Inflammation

A non-specific response to tissue damage aimed at destroying pathogens and beginning tissue repair.

Signs of inflammation

Redness, swelling, heat, and pain.

Complement system

A group of 20+ proteins produced by the liver that enhance the action of antibodies and phagocytes.

Mast cells

Specialised white blood cells that release histamine and heparin when tissue is damaged.

Histamine

A chemical that increases blood flow (vasodilation) and makes capillary walls more permeable.

Heparin

An anticoagulant that prevents clotting in the immediate area to allow phagocytes to reach the site of injury.

Phagocytes (Neutrophils)

Cells attracted to the injury site that consume micro-organisms and cellular debris.

Pus

A fluid formed at the site of infection consisting of dead phagocytes, tissue fluid, and dead pathogens.

Fever

An elevation of body temperature above 37°C, controlled by the hypothalamus in response to infection.

Pyrogens

Chemicals (like Interleukin-1) released by white blood cells that signal the hypothalamus to reset the body's thermostat higher.

Interleukin-1

A specific pyrogen produced by macrophages that also increases T-lymphocyte production.

Chill phase

The onset of fever where the body uses shivering and vasoconstriction to reach a new, higher temperature set-point.

Crisis phase

The stage where the fever "breaks," leading to sweating and vasodilation as the thermostat returns to 37°C.

Interferons

Proteins produced by virus-infected cells that help prevent the replication of viruses in neighbouring cells.

Benefits of fever

Inhibits pathogen growth, speeds up metabolic repair, and increases heart rate to deliver WBCs faster.

Risks of fever

Temperatures above 44.4°C can cause convulsions, brain damage, or death

Lymphatic system

A network of vessels and nodes that returns escaped fluid to the blood and filters out pathogens.

Lymph

The clear fluid collected from tissues containing cell debris, foreign particles, and micro-organisms.

Lymph nodes

Small, bean-shaped structures that trap bacteria and foreign particles in a mesh of fibres.

Lymphatic macrophages

Cells within lymph nodes that phagocytose (destroy) trapped pathogens.

Lymphocytes

White blood cells that increase in number during infection, causing lymph nodes to become swollen and sore.