Which statement best defines active immunity?

Which statement best defines active immunity?

• A. The body produces its own antibodies against disease-causing antigens.
• B. The body receives antibodies from another source.
• C. Immunity present at birth from genetic factors.
• D. Immunity gained through vaccination that does not involve antibody production.

Answer: (A)

Active immunity happens when the body's immune system actively responds to an antigen by making its own antibodies and memory cells, leading to long-lasting protection. This is exactly what occurs when B cells are activated by disease-causing antigens and differentiate into antibody-producing plasma cells, with memory cells remaining to respond quickly if the same pathogen reappears. The statement that best defines this concept is that the body produces its own antibodies against disease-causing antigens. In contrast, immunity gained from receiving antibodies from another source is passive immunity, which provides immediate but temporary protection. Immunity present at birth from genetic factors refers to innate or natural immunity, not the body’s active production of antibodies. Immunity from vaccination is considered active because vaccines stimulate the body's own immune system to produce antibodies and memory, rather than simply providing antibodies from an external source; a claim that vaccination does not involve antibody production contradicts how vaccines work.

Active immunity happens when the body's immune system actively responds to an antigen by making its own antibodies and memory cells, leading to long-lasting protection. This is exactly what occurs when B cells are activated by disease-causing antigens and differentiate into antibody-producing plasma cells, with memory cells remaining to respond quickly if the same pathogen reappears. The statement that best defines this concept is that the body produces its own antibodies against disease-causing antigens.

In contrast, immunity gained from receiving antibodies from another source is passive immunity, which provides immediate but temporary protection. Immunity present at birth from genetic factors refers to innate or natural immunity, not the body’s active production of antibodies. Immunity from vaccination is considered active because vaccines stimulate the body's own immune system to produce antibodies and memory, rather than simply providing antibodies from an external source; a claim that vaccination does not involve antibody production contradicts how vaccines work.