Detection of a truly chemotactic lymphokine for human monocytes using millipore membranes

The detection of the lymphokine monocyte chemotactic factor by determination of the leading front of monocyte migration is described. Stimulated and control supernatants were placed on the attractant side of cellulose ester filters with normal human monocytes as responder cells. Lymphokine activity was assessed by comparing the leading front of monocyte migration in response to control and stimulated culture supernatants. More monocytes migrated to all levels within the filters towards PHA stimulated culture supernatant than to control supernatant, indicating that the lymphokine acted on the entire migrating cell population and not only the cells at the leading front. Analysis of cell migration in a range of concentration gradients demonstrated that the lymphokine induced by PHA was chemotactic for monocytes. There was a significant association (p less than 0.01) between the production of monocyte chemotactic factor in vitro and skin test reactivity in vivo to three soluble antigens, SKSD, Candida albicans extract and tetanus toxoid. It is concluded that the detection of monocyte chemotactic factor production in vitro provides good evidence of sensitisation, however due to a number of false negative reactions, failure to detect the lymphokine does not necessarily indicate lack of reactivity in vivo.