C3.2 Defence against disease - reading task
If a disease-causing organism, a pathogen, comes into contact with the body it could cause infection and disease. Examples of pathogenic organisms include viruses, bacteria, fungi and protists. The body is adapted to prevent them entering the body; the skin and mucus membranes form the primary defence. However, if the pathogen evades this first barrier then white blood cells called phagocytes and lymphocytes act to...