If the surface barriers of innate immunity, such as the skin or mucous membranes are breached, the second line of defense in innate immunity is (are) the:

If the surface barriers of innate immunity, such as the skin or mucous membranes are breached, the second line of defense in innate immunity is (are) the:  lymphocytes

Explanation:

The lymphocytes direct and regulate immune responses. Specifically, B lymphocytes produce antibodies to fight against bacteria, viruses and invading toxins. T lymphocytes destroy the body's own cells that have been infected by viruses or that are cancerous.

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