Certified in Public Health (CPH) Practice Exam

What type of immunity is provided by immunoglobulin G (IgG)?

1. Innate immunity

2. Active immunity

3. Passive immunity

4. Cell-mediated immunity

The correct answer is: Active immunity

Immunoglobulin G (IgG) is a key player in the immune system, functioning primarily through the mechanisms of active immunity. Active immunity occurs when an individual's immune system is actively involved in developing a response to a pathogen, which includes producing antibodies following exposure to an antigen, either through infection or vaccination. IgG is the most abundant type of antibody found in the blood and extracellular fluid, equipping the body to fight off infections more effectively. It plays a crucial role in neutralizing toxins, opsonizing pathogens for phagocytosis, and activating the complement system, which helps in targeting and eliminating pathogens. While passive immunity is related to the transfer of antibodies from one individual to another—such as from mother to child during pregnancy or breastfeeding—IgG itself does not originate from this process in a healthy individual but rather results from the immune system's response to an infection or vaccine. Innate immunity refers to the body’s first line of defense that is not specific to any pathogen, and cell-mediated immunity primarily involves T-cells rather than antibodies like IgG. Thus, the classification of IgG as a component of active immunity highlights its role in specifically targeted immune responses developed by the host’s own immune mechanism.