Minimum of 250 words with at least 2 peer review reference in 6th edition APA format. Explain the differences between the primary and secondary line of defense. What factors interfere with these mechanisms? How are these levels of

Minimum of 250 words with at least 2 peer review reference in 6th edition APA format. Explain the differences between the primary and secondary line of defense. What factors interfere with these mechanisms? How are these levels of immunity affected in a child, an elderly person, or a person with a chronic disease?