When a pathogen or bacteria is recognized by the immune system, the adaptive immune response is activated, leading to the production of two main types of cells: effector cells and memory cells.
a) Effector Cell: Effector cells are responsible for carrying out the immediate response to eliminate the pathogen or bacteria. In the context of the adaptive immune response, there are two primary types of effector cells being Cytotoxic T cells (CD8+ T cells) & B cells.
b) Memory Cell: Memory cells are long-lived cells that "remember" the specific antigen from a previous encounter with a pathogen or bacteria. They are derived from the same activated cells that give rise to effector cells. If the same pathogen is encountered again in the future, memory cells can quickly respond and initiate a faster and more effective immune response.