An improved method for the in vitro evaluation of monocyte leukotaxis.

An adaptation of the double-filter technique has been developed for the in vitro evaluation of monocyte leukotaxis. The assay, which employs a sandwich of a cell-permeable polycarbonate and a cell-impermeable cellulose nitrate filter membrane, is more reliable, reproducible, and sensitive than previous techniques without sacrificing their rapidity and simplicity. Leukotactic responses were directly proportional to monocyte concentrations varying from 1 X 10(5)/ml to 6 X 10(6)/ml. Kinetic studies indicated that there was a linear increase in leukotactic responses at incubation periods from 60 to 180 min. At incubation periods less than 60 min, leukotactic responses also increased linearly but at an accelerated rate. The leukotactic and chemokinetic effects of a leukoattractant may be discriminated and appear to exert antagonistic effects in this assay system.