Relationship between electrophoretic mobility and activation of human monocytes

Isolated human monocytes showed an increased electrophoretic mobility (EM) during incubation in vitro. However, when the monocytes were isolated after activation in a mixed leukocyte culture, they tended to maintain their original EM during culturing. Activated and non‐activated monocytes were compared with respect to their activities during lymphocyte transformation. The lymphocytes which were used to test the activities of both kinds of monocytes had been depleted of all accessory cells by a two‐step physical isolation procedure including coutercurrent centrifugal elutriation and cell electrophoresis. Non‐activated monocytes supported concanavalin A (Con A) ‐ induced transformation of the purified lymphocytes optimally when the culture medium was supplemented by fetal calf serum (FCS). If, however, activated monocytes were used in lymphocyte transformation tests, Con A induced optimal [ 14 C]thymine‐deoxyribose incorporation, even if FCS was replaced by autologous human plasma. The results suggest that there is a relationship between the stability of the EM of human monocytes and their ability to support lymphocyte proliferation during an in vivo immune response, when FCS is obviously not present.