White blood cell normal when it is part of healthy immune responses, which happen frequently. It is occasionally abnormal, when it is neoplastic or autoimmune in origin. A decrease below the lower limit is called leukopenia. This indicates a weakened immune system. The name "white blood cell" derives from the physical appearance of a blood sample after centrifugation. White cells are found in the "buffy" "coat", a thin, typically white layer of nucleated cells between the sedimented red blood cells and the blood plasma. The scientific term "leukocyte" directly reflects its description. It is derived from the Greek roots "leuk-" meaning "white" and
Blood red wound, and it does not change color upon exposure to air. The color "blood red", therefore, covers both these states: the darker deoxygenated color and the brighter oxygenated one. Also, dried blood often has a darker, rust-colored quality: all dried blood has been oxygenated and then desiccated, causing the cells within it to die. This blood is often darker than either shade of red that can be seen in fresh blood. In the RGB color spectrum blood red often consists only of the color red, with no green or blue component; in the CYMK color model blood red has no