The Effect of Phorbol 12-Myristate 13-Acetate on CD11b and CD62-L Cell Surface Expression of Neutrophils and Monocytes

Background: Neutrophils and monocytes are phagocytic leukocytes that represent an important component of the non-specific immune system, by which invading micro-organisms and tumour cells are rapidly internalized and destroyed, via a number of biological mechanisms. Additionally, these phagocytic leukocytes play a key role in facilitating leukocyte-endothelial interactions in response to pro-inflammatory agents, during an inflammation. The expression of specific adhesion molecules such as CD62-L and CD11b, on the cell surface of neutrophils and monocytes, play an integral role with regards to cell migration, rolling, firm adhesion and subsequent cellular activation (leukocyte adhesion cascade). Leukocytes can be stimulated by chemotactic agents such as Phorbol 12-myristate 13-acetate (PMA). PMA is a direct stimulant of protein kinase C signaling pathway, which promotes cellular activation.

Methods: The aim of this pilot study was to determine the effect of PMA on CD62-L and CD11b cell surface expression of neutrophils and monocytes. Venous blood samples were collected from the ante-cubital fossa from healthy individuals, following written informed consent (n=4). Neutrophils and monocytes were isolated via a density gradient centrifugation method. Subsequently, neutrophil and monocyte cell surface expression of CD62-L and CD11b were measured by labelling with fluorescent anti-CD62-L and anti-CD11b monoclonal antibodies via flow cytometry.

Results: Following stimulation with PMA, monocytes displayed a decrease in CD62-L and increase in CD11b cell surface expression (p=0.103 and p=0.026 respectively). With respect to neutrophils, PMA resulted in a similar cellular response, where the cell surface expression of CD62-L decreased whilst CD11b increased (p=0.098 and p=0.025 respectively).

Discussion and Conclusion: In summary, this pilot study confirms the potent effect that PMA has on leukocyte function. Although studies involving PMA have previously been documented, this study provides a sound platform to continue work in this field of leukocyte biology. However, the validation and reliability of these findings would require to be assessed through the assessment of larger cohorts.