What is Acquired Immunity?
Acquired immunity, also known as adaptive immunity, refers to the immune response that develops after exposure to a specific
pathogen or following vaccination. Unlike
innate immunity, which is non-specific, acquired immunity is highly specific to the particular pathogen encountered. It involves the activation of
lymphocytes, which include B cells and T cells, and the production of antibodies.
How Does Acquired Immunity Work?
When a pathogen enters the body, it is detected by
antigen-presenting cells, which process and present antigens to T cells. This triggers a cascade of immune responses, including the activation of B cells that produce antibodies specific to the pathogen. These antibodies neutralize the pathogen and prevent it from infecting cells. Memory cells are also generated, providing long-term protection and enabling a faster response upon subsequent exposures to the same pathogen.
Active Immunity: This occurs when the immune system is exposed to a pathogen or its antigens, either through natural infection or vaccination. It is long-lasting because it involves the formation of memory cells.
Passive Immunity: This form of immunity is acquired through the transfer of antibodies from another source, such as maternal antibodies passed to a newborn through breast milk or the administration of immunoglobulin. Passive immunity provides immediate protection but is temporary as it does not involve the generation of memory cells.
Role in Vaccination
Vaccination is a critical application of acquired immunity in public health. Vaccines contain antigens or attenuated pathogens that stimulate the immune system to produce a protective response without causing disease. This prepares the immune system for future encounters with the pathogen, reducing the incidence and severity of infectious diseases. Vaccination has been instrumental in controlling and eradicating diseases such as smallpox and polio.
Why is Acquired Immunity Important in Epidemiology?
Acquired immunity plays a crucial role in
epidemiology by influencing the dynamics of infectious disease transmission. It determines the
herd immunity threshold, which is the proportion of the population that must be immune to prevent disease spread. Understanding acquired immunity helps epidemiologists design effective vaccination programs and predict the impact of interventions on disease outbreaks.
Challenges in Acquired Immunity
Despite its benefits, acquired immunity faces several challenges. Pathogen
antigenic variation can lead to immune evasion, as seen in influenza and HIV, requiring the development of new vaccines. Additionally, some individuals may not respond adequately to vaccination due to
immunocompromised states or genetic factors, highlighting the need for personalized approaches in immunization strategies.
Future Directions
Advancements in immunology and biotechnology are opening new avenues for enhancing acquired immunity. The development of vaccines using novel platforms such as mRNA and vector-based systems offers promising potential for protecting against emerging pathogens. Understanding the mechanisms of acquired immunity at the molecular level will further inform strategies to optimize vaccine efficacy and address challenges posed by evolving pathogens.
