Which of the following belongs to the first line of defence against infection?
- A. Production of antibodies by plasma cells
- B. Intact skin and the mucous membranes of the body openings
- C. Activation of cytotoxic T lymphocytes
- D. Formation of memory cells after an infection
Explanation
The first line is a physical and chemical barrier that stops pathogens entering at all: unbroken skin, mucus that traps microbes, cilia that sweep them out and acidic secretions. It is non specific, acting the same way against every organism, and it needs no previous exposure. Antibodies, T cells and memory cells all belong to the third line, the specific immune response.