S: (n) lymphocyte, lymph cell (an agranulocytic leukocyte that normally makes up a quarter of the white blood cell count but increases in the presence of infection)
S: (n) B cell, B lymphocyte (a lymphocyte derived from bone marrow that provides humoral immunity; it recognizes free antigen molecules in solution and matures into plasma cells that secrete immunoglobulin (antibodies) that inactivate the antigens)
S: (n) T cell, T lymphocyte (a small lymphocyte developed in the thymus; it orchestrates the immune system's response to infected or malignant cells)
S: (n) plasma cell, plasmacyte (a cell that develops from a B lymphocyte in reaction to a specific antigen; found in bone marrow and sometimes in the blood)