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
U2 Live at Red Rocks: Under a Blood Red Sky in October 1983 to promote U2's companion live mini-LP "Under a Blood Red Sky", which was released the following month. The mini-LP, whose name was later used as a subtitle for the concert film, features eight live songs from the War Tour, two of which ("Gloria" and "Party Girl") were taken from the Red Rocks concert; the other tracks were taken from performances in Boston and West Germany, as U2 thought they were "more developed performances". "U2 Live at Red Rocks: Under a Blood Red Sky" was U2's first home video release, initially released on VHS and Betamax by MCA