Characterisation of degranulation and phagocytic capacity of a human neutrophilic cellular model, PLB-985 cells

Exocytosis of neutrophil granules is a major event that converts circulating neutrophils into fully activated cells capable of chemotaxis, phagocytosis and destruction of pathogens. The PLB-985 cell line is a suitable neutrophilic cellular model which is utilised to study the different functional responses of neutrophils. In this study, we characterised the differentiation of PLB-985 cells toward the granulocytic pathway, using three different inducing agents: dbcAMP, DMSO and DMF. The differentiation efficiency was monitored by observation of cell morphology with electron microscopy, and by analysis of the expression of receptors such as FPRL1 and FcγRIIA, the distribution or release of granule markers, phagocytic capacity, as well as measurement of fMLF-induced calcium fluxes. Exocytosis and phagocytosis in differentiated cells were weaker as compared to neutrophils. fMLF stimulated primary granule exocytosis in cells differentiated with dbcAMP, DMSO and DMF, whereas the release of the contents of tertiary granules, as well as that of secretory vesicles, was only observed in dbcAMP-differentiated cells. DMSO-differentiated cells exhibited the highest phagocytic capacity. Altogether our results reinforce the fact that depending on the differentiating agent used, PLB-985 cells represent a useful model to study neutrophil functions and to bypass difficulties inherent to these primary cells.