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Background/aim: Serum-derived macrophage activating factor (serum-MAF) is expected to have adjuvant effects through rapid phagocytic activation, which depends on F-actin accumulation in multi-layered membrane ruffles induced within 5 min after serum-MAF addition. This study aimed to elucidate the importance of annexin A2, which is a multifunctional Ca 2+ -binding protein related to cytoskeletal membrane dynamics, in serum-MAF signalling., Materials and Methods: Annexin A2 and F-actin localizations were analyzed via immunostaining and confocal microscopy. Using EGTA as chelator, the role of Ca 2+ in serum-MAF signalling was examined., Results: Annexin A2 was found to translocate from the cytosol to the cell cortex within 30 s of serum-MAF stimulation. Ca 2+ chelation inhibited the translocation of annexin A2, frill-like structure formation, and phagocytic activation by serum-MAF., Conclusion: Annexin A2 and Ca 2+ were responsible for the rapid phagocytic activation by serum-MAF. This study provides an understanding of phagocytic activation in macrophages, which could be beneficial for cancer immunotherapy., (Copyright © 2021 International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Serum-derived macrophage activating factor (serum-MAF) can rapidly activate macrophage phagocytic activity by inducing characteristic membrane ruffles designated as Frill-like structures. Serum-MAF contains γ-globulin, an activator of phagocytosis. This study examined whether serum-MAF and γ-globulin activate macrophages similarly., Materials and Methods: Morphological changes in macrophages were observed by time-lapse imaging and the efficiency of engulfment was analysed quantitatively. Immunological staining of talin-1 and a calpain inhibitor were performed., Results: The engulfment efficiency of serum-MAF- and γ-globulin-activated macrophages was significantly different. Talin-1 showed weak co-localisation with the Frill-like structures. Treatment with a calpain inhibitor similarly down-regulated phagocytosis irrespective of the activation factor., Conclusion: There was a difference between macrophage activation mechanisms by γ-globulin and serum-MAF. Talin may slightly contribute to serum-MAF activation. It is possible to distinguish between the calpain-dependent fundamental 'mechanism of phagocytosis' and the activating factor-dependent rapid 'activation mechanism'., (Copyright© 2020, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Serum-derived macrophage activating factor, serum-MAF, is known to increase the phagocytic activity of macrophages by enhancing the engulfment efficiency. To elucidate the mechanisms underlying phagocytic activation, morphological changes were observed and analyzed., Materials and Methods: Morphological changes in macrophages were observed and quantitatively analyzed using scanning electron microscope (SEM) and confocal microscope., Results: SEM and confocal microscopy images revealed frill-like structures and active actin accumulations, respectively, in serum-MAF treated macrophages. Actin accumulation was induced within 5 min following serum-MAF treatment., Conclusion: Serum-MAF induced a rapid rearrangement of cytoskeletal actin and enhanced phagocytic activity. Findings of the current study may contribute to the development of techniques that facilitate activation of the human immune system, which in turn may be beneficial for cancer immunotherapy., (Copyright© 2019, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)

Background/aim: Serum-derived macrophage activating factor (serum MAF) is known to increase the phagocytic activity of macrophages and potentially plays a role in activating cancer immunity. In order to reveal the contributing factors for phagocytic activation, the migratory activity and the efficiency of engulfment was analyzed., Materials and Methods: THP-1 macrophages were induced by 12-O-tetradecanoyl-13-acetate (TPA). The migratory activity and efficiency of engulfment were analyzed by time-lapse imaging and suspension assay, respectively., Results: While the distance of migration did not change before and after activation with serum MAF, the efficiency of beads internalisation was significantly increased., Conclusion: Phagocytic activation of serum-MAF-treated macrophages was caused by increasing the efficiency of engulfment. This study contributes to the knowledge about the activation of the immune system through phagocytic activation of macrophages., (Copyright© 2018, International Institute of Anticancer Research (Dr. George J. Delinasios), All rights reserved.)