Worksheet 5 A. Fill in the blanks. 1. The ability of an organism to fight against infections and harmful substances is called 2. The cells produce antibodies in response to an antigen 3. Some common examples of are dust, mould, pollen, insect stings and nurs and get swollen 4. During an asthma attack, the B. Name the four tests that are used to check if someone is allergic to a substance.