Images Dated 3rd January 2003

Immunofluorescent LM of natural killer blood cells

Natural killer cell. Immunofluorescent light micrograph of human Natural Killer (NK) cells. The nucleus of each cell is blue, with the cytoplasm proteins stained green, yellow and red. Natural killer cells are a type of white blood cell known as T-lymphocytes. As part of the body's immune response mechanism, NK cells have the ability to destroy virus-infected cells & tumour cells. On contact with the surface of a tumour cell, the NK cell recognizes certain proteins called antigens, which activate its cell-killing mechanism. Immunofluorescence uses antibodies to attach fluorescent dyes to specific molecules within cells. Magnification: x624 at 6x4.5cm size

© NANCY KEDERSHA/SCIENCE PHOTO LIBRARY

Photograph of Charles Darwin in 1881, aged 72

Charles Darwin. Photograph of English naturalist Charles Robert Darwin (1809-1882) in 1881, aged 72. As a young man Darwin briefly studied medicine then trained in the clergy, but his interest was in natural history. In 1831 he set sail as naturalist on HMS Beagle, which was to provide the fieldwork for his famous book: Origin of Species (1859). His theory of natural selection suggested that natural variation in a species creates a wide range of individual traits, some more useful than others. Competition to survive provides a driving force for evolution in the form of natural selection. His theory fuelled bitter controversy. Darwin is buried in Westminster Abbey

© SCIENCE PHOTO LIBRARY