Chemotaxis of leucocytes: an improved method of direct microscopic observation.

Leucochemotaxis was evaluated by direct morphological observation of a cell suspension between slide and coverslip. The chemotactic index was obtained by the ratio of the number of moving leucocytes recorded within an area limited on the slide by circles traced, at the beginning and after a time period of exposure to a gradient of chemotactic factor which was placed in the center of the circle in dry state. The optimal conditions (times of exposure, pH of the medium) and the reproducibility of the assay were investigated on normal blood samples.