CD45 is not involved in the processing of spatial information required for chemotaxis.

To examine the possible role of CD45 (a cell surface tyrosine phosphatase) in processing spatial information leading to the orientation of neutrophils in a gradient of chemoattractant, we used antibodies to cap CD45. If the phosphatase activity of CD45 was processing spatial information coming from occupied receptors and leading to the directional cell response, sequestering CD45 in one region of the cell surface should lead to a decreased ability of the cells to orient in a gradient of chemoattractant. CD45 was capped by sequential addition of KC56, a mAb against CD45, and a rabbit anti-mouse antiserum. Cells with capped CD45 were able to orient toward N-formylnorleucylleucylphenylalanine and C5a at levels similar to those achieved by cells processed simultaneously but without capping CD45. This indicates that the spatial arrangement of CD45 is not critical for the ability of cells to orient in a gradient of chemoattractant.