Macrophages are widely distributed across nearly all tissues of the body — from the epidermis and cornea to avascular joints. As the only immune cell type present in every organ, macrophages play essential roles in homeostasis, immunity, and disease progression. Understanding their functions often requires macrophage depletion, an indispensable approach in immunology and pathophysiology research.
Among available depletion strategies, clodronate liposomes have become the most established, convenient, and cost-effective tool for eliminating macrophages in vivo. This blog walks you through the fundamentals of macrophage depletion — including its mechanism, dosing routes, marker selection, and representative literature — so you can confidently design your next macrophage-targeting experiment.
1. Introduction to Macrophage Depletion
Macrophage depletion allows researchers to dissect the functional contributions of macrophages under physiological and pathological conditions. While generating macrophage knockout models provides genetic specificity, it is often time-consuming and expensive.
In contrast, clodronate liposomes (Clodronate Liposomes, CLOD-LIP) offer a fast, reproducible, and economical alternative. They effectively remove macrophages from diverse tissues such as the liver, spleen, lung, and blood, and have been widely adopted as a standard macrophage depletion method in both immunology and oncology research.
2. Mechanism of Action
Clodronate liposomes are formed by encapsulating clodronate (a bisphosphonate compound) within phospholipid vesicles. The clodronate molecules themselves cannot cross the lipid bilayer freely.
Once injected into the body, the liposomes are phagocytosed by macrophages. Inside the lysosome, the liposomal membrane is degraded by phosphatases, releasing clodronate into the cytoplasm. When intracellular concentrations reach a cytotoxic threshold, clodronate triggers irreversible apoptosis of the macrophage.
Dead cells then release clodronate, which is safely excreted via urine — making this approach both effective and biologically contained.
3. Dosing and Administration
Macrophage depletion efficiency depends on the administration route, tissue type, and mouse strain. The following are commonly used dosing parameters for C57BL/6J mice:
Table 1. Macrophage Depletion Protocol in C57 Mice
|
Administration Route |
Typical Dose |
Frequency |
|
Intraperitoneal (i.p.) injection |
150–200 μL per mouse (20–25 g) |
Single or repeated every 3–7 days |
|
Intravenous (i.v.) injection |
150–200 μL per mouse |
Single dose for systemic depletion |
|
Intranasal administration |
Dose optimized per model |
For lung-resident macrophages |
4. Macrophage Markers
Macrophages are heterogeneous, with distinct subsets across organs. Marker selection is therefore critical when assessing depletion efficiency by flow cytometry or immunostaining.
Below are selected examples from published literature:
Table 2. Markers of Macrophage Subtypes
Source: Klopfleisch R. Macrophage reaction against biomaterials in the mouse model - Phenotypes, functions and markers. Acta Biomater. 2016 Oct 1;43:3-13. doi: 10.1016/j.actbio.2016.07.003. Epub 2016 Jul 6. PMID: 27395828.
Table 3. Markers of Macrophages in Different Tissues
|
Tissue |
Macrophage Type |
Representative Markers |
|
Adipose tissue |
Adipose macrophages |
CD45⁺, F4/80⁺, PPARγ⁺ |
|
Liver |
Kupffer cells |
CD68⁺, F4/80^high⁺, CD169⁺, Siglec-1⁺ |
|
Lung (alveolar) |
Alveolar macrophages |
CD11c^high⁺, F4/80^low⁺, CD206⁺, Siglec-F⁺ |
|
Bone marrow |
Bone marrow macrophages |
F4/80⁺, CD169⁺, VCAM1⁺ |
|
Intestine |
Intestinal macrophages |
F4/80⁺, CD11b⁺, CX3CR1^high⁺ |
5. Representative Studies
Numerous studies have demonstrated the effectiveness of clodronate liposomes in various mouse models:
Peripheral Blood Depletion
Xiong et al., 2022, Signal Transduct Target Ther (IF: 18.19)
- C57BL/6J mice, i.p. injection of 200 μL clodronate liposomes.
- Flow cytometry (F4/80⁺) confirmed a significant reduction in circulating macrophages 24 h post-injection.
Peritoneal Macrophage Depletion and Reconstitution
Zhang et al., 2022, Mol Cell (IF: 17.97)
- Female C57BL/6J mice received 15 mg/kg on days 0, 3, and 6.
- Peritoneal macrophages (CD11b⁺/F4/80⁺) were effectively cleared, followed by bone marrow–derived macrophage reconstitution.
Systemic and Mammary Macrophage Depletion
Cai et al., 2022, Adv Sci (IF: 17.52)
- Intravenous injection (200 μL per mouse) depleted macrophages in blood and mammary glands within 48–72 h.
Tumor Immunology Model
Yu et al., 2022, J Immunother Cancer (IF: 12.47)
- i.p. injection (200 μL) effectively removed macrophages from peripheral blood before PD-L1/TLR7 dual-target therapy.
These examples demonstrate that clodronate liposomes offer robust and reproducible macrophage depletion across multiple tissue contexts.
6. Product Information
Clodronate liposomes(Cat#40337ES) have revolutionized how researchers study macrophage function. By combining convenience, cost-effectiveness, and versatility, they remain the go-to solution for macrophage depletion in immunology, oncology, and infectious disease research.
Each 1 mL of clodronate liposome suspension (particle size ~1.5–2 μm) contains approximately 5 mg of clodronate, formulated in 10 mM Na₂HPO₄, 10 mM NaH₂PO₄, and 140 mM NaCl.
This ready-to-use formulation provides reliable macrophage depletion while maintaining biocompatibility and ease of handling.
Whether you’re studying immune regulation, tissue remodeling, or therapeutic response, this tool can help you remove the macrophage “noise” and reveal the true signals driving your biology.
Related Product
|
Name |
Cat. No. |
Size |
|
40337ES08/10 |
5 mL/10 mL |
|
|
40338ES08/10 |
5 mL/10 mL |