Which is not an effector T lymphocyte? cytotoxic T lymphocyte memory T lymphocyte helper T lymphocyte

Immune system produce two types of cells such as B lymphocytes (B cells) and T lymphocytes (T cells). B cells are produced and matured in the bone marrow whereas T cells are produced in the bone marrow and matured in the thymus gland. 

Immune system stimulates either B cells or T cells upon invasion of foreign bodies or pathogens into the body. B cells produce antibodies and T cells produce cytotoxic cells and helper T cells upon stimulation. A type of cells that performs specific function in response to immune stimulation is referred to as effector cells.