Relation to chemotactic factor gradients to neutrophil migration and orientation under agarose

Chemotactic substances confer a migratory pattern for neutrophil granulocytes under agarose that is characteristic for each agent. To analyse the cause of such differences, we have studied neutrophil migration and orientation with f-Met-Leu-Phe (fMLP), leukotriene B4 (LTB4), and serum as chemoattractants. When these agents were used at optimal concentrations, it was observed that cells stimulated by LTB4 did not start migration as fast and did not migrate as far as those exposed to fMLP, but they maintained a higher degree of orientation. This delay in initiation of migration and maximal degree of orientation was even more marked when serum was the chemoattractant. These migration variables were related to the generation of gradients in the agarose of fML[3H]P, arachidonic-[3H]acid (AA, of which LTB4 is a metabolite), and fluorescein. The curvilinear AA gradient was flatter and more stable than those of fML[3H]P and fluorescein, which were linear. Thus, differences in the development and shape of the gradient of chemoattractant may contribute to differences in migration kinetics.