Long-term immunity is predominantly facilitated by memory T and B cells. These cells are a critical component of the adaptive immune response. When the body is exposed to a pathogen, B cells produce antibodies that target specific antigens, while T cells play various roles including killing infected host cells and assisting other immune cells.
Following an initial immune response, a subset of these T and B cells persists as memory cells. Memory T cells remain in circulation and can quickly respond to subsequent exposures to the same pathogen, often leading to a faster and more effective response upon re-infection. Similarly, memory B cells can rapidly produce antibodies upon re-exposure, which helps in neutralizing the pathogen more effectively and swiftly.
In contrast, while natural killer cells, macrophages, and helper T cells play significant roles in the immune response, they do not maintain the long-term immunological memory that is crucial for enduring immunity. Macrophages and natural killer cells are part of the innate immune system and primarily respond to immediate threats without the specificity and memory characteristic of the adaptive immune cells. Helper T cells aid in orchestrating the immune response but do not retain specific memory for long-term immunity like memory B and T cells do.