What type of immune response is present when memory cells are formed?

The formation of memory cells is a hallmark of the adaptive immune response. When the body encounters a pathogen for the first time, it initiates a specific immune response that includes the activation of B and T lymphocytes. These activated cells can differentiate into memory cells after the infection is cleared. Memory T cells are responsible for cell-mediated immunity, while memory B cells can quickly produce antibodies upon re-exposure to the same pathogen. This process allows for a more rapid and robust immune response during subsequent encounters with the same pathogen, providing long-lasting immunity.

In contrast, innate immunity is the body's first line of defense and acts quickly but does not create memory cells. Passive immunity involves the transfer of antibodies from one individual to another (like from mother to infant), and it does not involve the formation of memory cells. Natural immunity refers to immunity that develops as a result of natural exposure to pathogens rather than vaccination, but this too does not specifically focus on the generation of memory cells as a defining feature. The adaptive immune response, characterized by memory cell formation, is critical for long-term immunity and is fundamental to the functioning of vaccines.