Changes in neutrophil right-angle light scatter can occur independently of alterations in cytoskeletal actin.

Forward-angle light scatter (FALS) and right-angle light scatter (RALS) are commonly employed to discriminate between leukocyte subclasses. Recently the application of RALS has expanded, and it is now also used as an indicator of neutrophil actin polymerization. In this communication we critically examine the relationship of RALS to changes in cytoskeletal actin. The data indicate that agonists which stimulate an increase, a decrease, or no change in F-actin content can all stimulate a biphasic change in RALS. We therefore conclude that changes in RALS can occur independently of changes in F-actin content. This leads us to suggest that caution must be taken when interpreting RALS data in relation to changes in F-actin. Furthermore, the data also support the idea originally proposed by Yuli and Snyderman (J Clin Invest 73:1408-1417, 1984), that RALS may be an exceptionally sensitive indicator of cell activation.