Leucocyte-associated plasma proteins. I. Plasma proteins in supernatants and cell pellets during successive washings of human blood cells.

Sixteen plasma proteins were studied in the supernatants from 20 successive washings of human leucocytes by a new sensitive immunoelectrophoretic method. In the first few supernatants a fast and parallel decrease in concentration of all proteins took place, but for 11 proteins this was followed by a phase of slow decrease due to cellular release. Eight proteins could be quantitated throughout the 20 washings: prealbumin, albumin, orosomucoid, alpha 1-antitrypsin, transferrin, C3, haptoglobin, and IgG. These proteins and trace amounts of eight other plasma proteins were present in the cell lysate after the washings. In comparison with plasma, the leucocytes contained relatively higher concentrations of prealbumin, orosomucoid, alpha 1-antitrypsin, and haptoglobin than of albumin. In crossed immunoelectrophoresis these same four proteins were present as molecular variants differing from their plasma counterpart in electrophoretic mobility and morphology of the precipitate.