CD44 mediates polymorphonuclear leukocyte motility on hyaluronan

To investigate the behavior of polymorphonuclear (PMN) leukocytes on the extracellular matrix carbohydrate component, hyaluronan (HA), in the presence and absence of the chemokine, interleukin-8 (IL-8).

The present study was conducted at the Department of Hematology, University of Liverpool, United Kingdom, between the period 2000 to 2001. Polymorphonuclear cells were isolated from whole venous blood using Mono-Poly-Resolving Medium. Purified PMN were added alone or with IL-8 to HA-coated plates and the behavior of these cells monitored by time-lapse video microscopy over a period of 40 minutes. For the identification of surface receptor(s) mediating PMN migration on HA, PMN were incubated with blocking and non-blocking antibodies against cluster of differentiation 44 (CD44) and Receptor for Hyaluronan Mediated Motility (RHAMM) prior to addition to HA-coated surfaces.

Approximately 55% of PMN were found to interact and migrate on HA-coated plates with a mean speed of 6.4 +/- 0.7 mm/min. Addition of IL-8 reduced both the percentage moving cells (7.5%) and the average speed of the remaining moving cells (2.0 +/- 0.3 mm/min). The inhibitory effect of IL-8 on PMN migration was associated with reorganization of the cytoplasmic fibrillar form of actin. Anti-CD44 blocking antibody substantially reduced the speed of PMN (2.5 +/-0.9 mm/min), while non-blocking anti-CD44 and anti-RHAMM antibodies had no effect.

The present study demonstrates for the first time that PMN are able to interact and migrate on the widely distributed extracellular matrix component, HA, using the cell surface receptor, CD44. Such interaction is modified by the chemokine, IL-8, in a way that optimizes the host defense against invading pathogens.