Orientation of PMN in a pH gradient: acid-induced release of a chemotactic factor

Human and rabbit PMN, placed in a gradient of pH 5 to pH 8 over 1 mm, orient their locomotion toward pH 5. This orientation is due to the release or production of a chemotactic factor by the cells in the acid pH. This activity can be recovered in the supernatant and is maximal when the cell incubation is at pH 5.5. Its appearance is rapid, occurring within 1 min, and is temperature dependent. Cells survive treatment at pH 5.5 and are capable of subsequently responding to chemotactic peptides.