IMMUNOLOGY

Detailed explanation-1: -Rapid and blunt, the innate immune system is the first line of defense. It recognizes a limited number of molecular patterns in disease-causing microbes, or pathogens. Convention says that the innate immune system retains no memory of previous infections.

Detailed explanation-2: -The body has two types of acquired, adaptive immunity: active and passive immunity. Active immunity refers to immunity acquired through the introduction of antigens, resulting in antibodies and memory cells.

Detailed explanation-3: -Active immunity involves the production of antibodies by the body itself and the subsequent development of memory cells. Passive immunity results from the acquisition of antibodies from another source and hence memory cells are not developed.