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Updated: May 15, 2026
Assessing Retinal Microglial Phagocytic Function In Vivo Using a Flow Cytometry-based Assay
Published on: October 18, 2016
Glatiramer acetate increases phagocytic activity of human monocytes in vitro and in multiple sclerosis patients
Refik Pul1, Franco Morbiducci, Jelena Škuljec
1Department of Neurology, Hannover Medical School, Hannover, Germany.
Abstract:
Beside its effects on T cells, a direct influence on cells of the myelo-monocytic lineage by GA becomes evident. Recently, we demonstrated that GA drives microglia to adopt properties of type II antigen presenting cells (APC) and increases their phagocytic activity. In the present work, we focused on human blood monocytes in order to examine whether GA may increase phagocytic activity in vivo and to evaluate the molecular mechanisms explaining this new discovered mode of action. Peripheral blood mononuclear cells (PBMC) were obtained using a Biocoll-Isopaque gradient and monocytes were subsequently isolated by using CD14 MicroBeads. Phagocytic activity was determined by flow cytometric measurement of the ingestion of fluorescent beads. Flow cytometry was also used to assess monocytic differentiation and expression of phagocytic receptors. Monocytes of GA treated MS patients exhibited a significantly higher phagocytic activity than those of healthy controls or non-treated MS patients. In vitro, a significant phagocytic response was already detectable after 1 h of GA treatment at the concentrations of 62.5 and 125 µg/ml. A significant increase at all concentrations of GA was observed after 3 h and 24 h, respectively. Only monocytes co-expressing CD16, particularly CD14(++)CD16(+) cells, were observed to phagocytose. Treatment of monocytes with IL-10 and supernatants from GA-treated monocytes did not alter phagocytosis. We observed a decrease in CD11c expression by GA while no changes were found in the expression of CD11b, CD36, CD51/61, CD91, TIM-3, and CD206. In our blocking assays, treatment with anti-CD14, anti-CD16, anti-TIM3, anti-CD210, and particularly anti-CD36 antibodies led to a decrease in phagocytosis. Our results demonstrate a new mechanism of action of GA treatment that augments phagocytic activity of human monocytes in vivo and in vitro. This activity seems to arise from the CD14(++)CD16(+) monocyte subset.
Insights
Glatiramer acetate (GA) treatment enhances the phagocytic activity of human monocytes, particularly the CD14++CD16+ subset. This novel mechanism of action increases the cells' ability to engulf particles, offering new insights into GA's therapeutic effects.
Area of Science:
- Immunology
- Cell Biology
- Neuroscience
Background:
- Glatiramer acetate (GA) is known to affect T cells.
- Recent studies show GA enhances microglial antigen-presenting cell (APC) properties and phagocytosis.
- A direct influence of GA on myeloid cells, including monocytes, is increasingly evident.
Purpose of the Study:
- To investigate if GA increases phagocytic activity in human blood monocytes.
- To elucidate the molecular mechanisms underlying GA-induced monocyte phagocytosis.
- To examine GA's effects in both in vivo and in vitro settings.
Main Methods:
- Isolation of peripheral blood mononuclear cells (PBMCs) and CD14+ monocytes.
- Flow cytometry to measure phagocytic activity (fluorescent bead ingestion).
- Assessment of monocytic differentiation and phagocytic receptor expression.
- Blocking assays using specific antibodies.
Main Results:
- GA-treated multiple sclerosis (MS) patients showed significantly higher monocyte phagocytic activity compared to controls.
- In vitro, GA increased phagocytosis in monocytes within 1-24 hours.
- Phagocytosis was primarily observed in CD14++CD16+ monocytes.
- GA treatment decreased CD11c expression but did not affect other tested receptors.
- Blocking antibodies against CD14, CD16, TIM-3, CD210, and CD36 reduced phagocytosis.
Conclusions:
- GA exhibits a novel mechanism of action by augmenting phagocytic activity in human monocytes.
- This effect is particularly pronounced in the CD14++CD16+ monocyte subset.
- GA's influence on monocyte phagocytosis may contribute to its therapeutic benefits in conditions like MS.
