Two-Dimensional Electrophoresis

We compared cellular proteins from normal human blood lymphocytes, monocytes, and granulocytes, using highresolution two-dimensional electrophoresis. The leukocytes were isolated from peripheral blood by centrifugation on density step gradients (yielding a fraction of purified granulocytes and a lymphocyte/monocyte mixture) and monocytes were subsequently separated from lymphocytes by virtue of their adherence to plastic. Wright-stained smears indicated that each of the three resulting fractions was 90 to 95% pure. The cells were labeled with [35S]_ methionine after various intervals in culture, then solubilized and analyzed by two-dimensional electrophoresis. Although most proteins in each cell type are common to all three, there are nevertheless several specific marker proteins that distinguish one cell type from another. We also examined the appearance of these markers in three lines of cultured cells from humans (GM607, a B-Iymphoblastoid line; HL-60, a promyelocytic leukemic line; and 1494, a normal skin fibroblast) .