Caption

Plasma cells. Coloured transmission electron micrograph (TEM) of plasma cells. Plasma cells are mature B lymphocytes (white blood cells) that produce and secrete antibodies during an immune response. The cell's nucleus (brown) contains dense chromatin (yellow), a complex of DNA (deoxyribonucleic acid) and proteins. In the cell's cytoplasm (green) is an extensive network of rough endoplasmic reticulum (RER, blue lines). RER manufactures, modifies and transports proteins, in this case antibodies. There are also a number of mitochondria (orange, oval) in the cytoplasm, which provide the cell with energy.