Helper T cell and B cell, SEM

Helper T cell (small cell) and B cell (large cell), coloured scanning electron micrograph (SEM). Both cells are specialized immune response cells (lymphocytes). Helper T cells are derived from the thymus. The helper and killer T cells exit and pass back into the bloodstream, ready to battle antigens. B cells reach their full antigen-fighting potential in the lymph nodes and spleen where antigens (foreign material) are filtered. When Helper T cells detect the presence of specific antigens, they produce various secretions that signal other cells to multiply and attack. Helper T cells instruct B cells to start making antibody-producing plasma cells and memory B cells. Helper T cells also foster the production of cytotoxic, or killer T cells. Helper T cells can also release interleukin which stimulates other T cells. B cells can also digest the foreign material. Magnification: x2,000 when shortest axis printed at 25 millimetres., by DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY