Florida Biology EOC Practice Test

The second line of defense refers to the non-specific immune response, which includes various components of the immune system that act quickly to combat pathogens without targeting specific invaders. This line encompasses responses such as inflammation, fever, and the action of phagocytes, which are white blood cells that engulf and destroy pathogens. These mechanisms are essential because they provide immediate protection to the body and help contain infections before the specific immune response is activated. In contrast, the first line of defense includes physical and chemical barriers such as skin and mucous membranes, while the third line of defense is the specific immune response that involves lymphocytes and the production of antibodies tailored to particular pathogens. The concept of a fourth line of defense is not standard in immunology. This distinction highlights how the non-specific response acts as a broad, generalized defense against a wide range of pathogens.