noun, plural: memory cells
A long-lived immune cell that has the ability to recognize a foreign particle that it previously encountered and consequently mount a faster and stronger immune response
Memory cells are long-lived immune cells capable of recognizing foreign particles they were previously exposed to (thus, the memory in their name). These immune cells do not respond immediately when it first encounters an antigen but facilitates a more rapid secondary response when the antigen is encountered on a subsequent occasion.
Examples of memory cells are memory B cells and memory T cells. Memory B cells are clones of a parent B cell that previously served as an antigen-presenting cell and then activated by a helper T cell to proliferate. As clones, the memory B cells bear the same B cell receptors as those of the parent B cell. Therefore, they would be able to detect the same antigen when re-exposed. Memory B cells produce more robust antibody-mediated immune response during re-infection.
Memory T cells are T lymphocytes that have the similar capability of recognizing foreign particles that they previously encountered. But unlike memory B cells, the memory T cells do not produce antibodies. Re-exposure to the pathogens causes them to clone themselves immediately and as such respond to the infection more strongly.