Name 4 ways the human body protects itself

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)

1) Vaccination causes the body to produce enough white blood cells to protect itself against a pathogen. 2)One simple way to reduce the risk of infection to maintain personal hygiene. 3) Skin is another one, its a stable, but flexible outer covering that acts as a barrier. 4)The blood cells and immune system. If germs get through the skin, the job of protecting the body shifts to the immune system. 
Hope this helps you! :)

The truman doctrine was an american foreign policy whose stated purpose was to counter soviet geopolitical expansion during the cold war. it was announced to congress by president harry s. truman on march 12, 1947, and further developed on july 12, 1948, when he pledged to contain threats to greece and turkey