Describe how pathogens cause infections and describe how the immune system defends the body against these pathogens.

Pathogens cause infection by entering the organism and infecting a host in order to reproduce. As they replicate themselves, the pathogen spreads and becomes more harmful. The immune system consists of lymphocytes and phagocytes which help kill the pathogen. The lymphocytes produce antibodies which can latch on and destroy invading viruses or bacteria. The phagocytes have the ability to ingest the pathogen by engulfing it.
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From a high concentration to a low concentration.