They are extremely important for antigen processing and presentation to lymphocytes. Many monokines have immunoregulatory functions. Macrophages can be cytotoxic and participate in antitumor and antiviral mechanisms. Mononuclear phagocytes are a prominent component of chronic inflammation. The two major types of lymphocytes are B cells and T cells.
B lymphocytes are responsible for humoral immunity and are precursors to plasma cells.
T lymphocytes are responsible for cell mediated immunity. T lymphocytes have various types of regulatory functions. Without special immunohistochemical stains, it is impossible to distinguish lymphocyte types morphologically. Plasma cells are responsible for production of immunoglobulins. The primary role of lymphocytes is in immune functions.