Kinetics analysis of binding between melanoma cells and neutrophils.

It has been determined previously that polymorphonuclear leukocytes, or PMNs, can facilitate melanoma cell extravasation through the endothelium under shear conditions. The interactions between melanoma cells and PMNs are mediated by the beta2-integrins expressed by PMNs and intercellular adhesion molecules (ICAM-1) expressed on melanoma cells. In this study, the kinetics of these interactions was studied using a parallel plate flow chamber. The dissociation rates were calculated under low force conditions for ICAM-1 interactions with both beta2-integrins, LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18), together and separately by using functional blocking antibodies on PMNs. The kinetics of PMNs stimulated with IL-8 was also determined. It was concluded that the small number of constitutively expressed active beta2-integrins on PMNs are sufficient to bind to ICAM-1 expressed on melanoma cells and that the intrinsic dissociation rate for these adhesion molecules appear to be more dependent on what method is used to determine them than on what cells express them.