Final answer:
Lymphocytes are leukocytes that become activated by antigens and differentiate into B cells and T cells. The effector response involves plasma cells producing antibodies.
Step-by-step explanation:
Lymphocytes are leukocytes that play a key role in the immune response. They become activated by a specific antigen and differentiate into B cells and T cells. The activation of lymphocytes occurs through a series of steps, starting with antigen encounter and presentation by B cells, which then attract helper T cells to release cytokines signaling the B cells to develop into plasma cells. The effector response involves plasma cells producing antibodies to fight pathogens.