What are the different types of immune responses?

Immune responses can broadly be classified into two main types – innate and adaptive. Both play crucial roles in defending the body against pathogens and foreign substances, but they differ in their mechanisms, timing, and specificity.

Innate Immune Response

The innate immune response is the body’s first line of defense to foreign substances. It is activated immediately on being attacked by a pathogen. Its ability to initiate an immediate response is because it lacks specificity. The innate immune response encompasses diverse physical barriers, cellular components and defense mechanisms including skin, hair, and mucous membranes, phagocytic cells such as neutrophils, macrophages, and dendritic cells, natural killer cells, and assorted proteins. The various components of the innate immune system work together to destroy foreign substances via different mechanisms by promoting an inflammatory response, and enhancing phagocytosis and cell-mediated killing. This type of immunity is present in an organism at birth.

Adaptive or Acquired Immune Response

The adaptive immune response develops throughout life. It typically develops after exposure to a disease or after immunization with vaccines. The adaptive immune response takes much longer to get activated and could take days or weeks to achieve full effectiveness. However, its inherent memory component provides long-lasting protection on re-infection by the same pathogen. The adaptive immune response exhibits outstanding specificity towards specific pathogens or foreign substances. T and B lymphocytes make up the core components of the adaptive immune system. There are several types of T lymphocytes. Some are responsible for directly killing infected cells while others help regulate other immune cells, prevent autoimmune reactions, or suppress excessive immune responses. B cells are responsible for synthesizing antibodies that specifically target antigens expressed on foreign pathogens.