DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY DENNIS KUNKEL MICROSCOPY / SCIENCE PHOTO LIBRARY
T lymphocytes (pre-T cells) and granulocyte (neutrophil), coloured scanning electron micrograph (SEM). Lymphocytes are involved in the specific immune response and are composed mainly of precursor T cells (pre-T cells) and B cells. Pre-T cells and B cells are subsets of lymphocytes that originate in the red bone marrow from hematopoietic stem cells. Pre-T cells circulate in the blood before migrating to the thymus where they develop into specialized cells (helper T cells and killer T cells) that are able to identify antigens and infected tissue cells. Granulocytes are leukocytes with granules in their cytoplasm that contain destructive chemicals. Neutrophils are involved in inflammation and other immune responses. They assist in cellular defence (phagocytosis) of pathogenic microorganisms. A neutrophil destroys an antigen by engulfing it and injecting lethal chemicals. Magnification: x1,600 when shortest axis printed at 25 millimetres.
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