Human peripheral blood accessory cell: isolation by hypotonic density gradient, functional, and phenotypical characterization.

In order to purify the human peripheral blood-derived accessory cell that cooperate with T lymphocytes in the process of mitogenic stimulation, we developed a new density gradient separation. This was based on the principle of hypotonic swelling of the cells to obtain a differential change of the buoyant densities of cells. By this method, we have obtained a highly accessory cell-depleted lymphocyte fraction whose proliferative response to sodium periodate stimulation was almost aborted. Another fraction containing high accessory cell activity was further divided into Fc-receptor-positive and -negative cells. The latter revealed the highest accessory activity for T lymphocyte periodate stimulation. The cells were characterized according to a number of markers and appeared to resemble lymphoid dendritic cells. Compared with the monocyte/macrophage fraction, they showed veils and dendritiform elongations and expressed reduced values of monocyte/macrophage specific markers. Compared with the high accessory activity of these cells, monocytes/macrophages expressed a low accessory activity.