Immune system - through a complex interaction between various types of immune cells, the body is able to decompose invading organisms
Immune system memory - information about the pathogens encountered during an illness is stored in immune cells and is used to quickly destroy those pathogens if they become present in the body again (basis for vaccines)
Metabolic adjustments - during severe infections or trauma, the body lowers the consumption of nutrients thus lowering the chances of introducing unwanted microorganisms or toxins into the bloodstream
Blood-Brain barrier - filters out larger molecules - effetively preventing many microorganisms from entering the brain
Sneezing, runny nose, sweat, high fever, vomitting - creates unfavorable microenvironment and expels decomposed (fully or partially) and active pathogens( bacteria, viruses, fungi)