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The Power of Flow Cytometry in Myeloid Tissue Analysis 

Published On 04/18/2024 2:53 PM
Myeloid Tissue Characterization: The Power of Flow Cytometry

Introduction to Myeloid Tissue and Flow Cytometry

Myeloid tissue, also known as bone marrow, is the soft, spongy tissue found in the hollow interior of bones. It is the primary site of new blood cell production or hematopoiesis. It produces more than 200 billion new blood cells every day.
The main components of myeloid tissue are:
 Cell Type Derived From Key Characteristics
 Hematopoietic Stem   Cells (HSCs) - Multipotent stem cells that initiate hematopoiesis, giving rise to all other blood cells.
 Myeloid Progenitor Cells Hematopoietic Stem Cells (HSCs) Can differentiate into several types of blood cells; progenitor to red blood cells, platelets, and all white blood cells except lymphocytes.
 Mature Myeloid Cells Myeloid Progenitor Cells Includes various cell types specialized in functions like oxygen transport, blood clotting, and immune defense.
 Erythrocytes (Red Blood   Cells) Myeloid Progenitor Cells Carry oxygen from the lungs to the rest of the body.
 Megakaryocytes/Platelets Myeloid Progenitor Cells Involved in blood clotting.
 Granulocytes (Neutrophils,   Eosinophils, Basophils) Myeloid Progenitor Cells Part of the innate immune system, primarily involved in defense against pathogens.
 Monocytes/Macrophages Myeloid Progenitor Cells Involved in phagocytosis and play a key role in the immune response to inflammation.
Table 1. A structured overview of the differentiation pathways and functions of various cells derived from hematopoietic stem cells within the myeloid lineage.
The myeloid tissue plays a crucial role in the immune system. The white blood cells it produces are key players in the body’s defense mechanism. Neutrophils are the most abundant white blood cells and are the first to arrive at the site of an infection. Eosinophils are involved in the immune response to parasitic infections and allergic reactions. Basophils play a role in allergic reactions and asthma. Monocytes, which differentiate into macrophages, are involved in phagocytosis and are key players in the immune response to inflammation.

In addition to their role in immunity, myeloid cells also contribute to the maintenance of homeostasis in the body. For example, red blood cells are responsible for the transport of oxygen from the lungs to the tissues, while platelets play a crucial role in blood clotting and wound healing.
However, abnormalities in myeloid tissue can lead to various health problems. Overproduction of myeloid cells can result in conditions such as polycythemia (an excess of red blood cells) and thrombocytosis (an excess of platelets), while underproduction can lead to anemia (a deficiency of red blood cells) and thrombocytopenia (a deficiency of platelets). Furthermore, mutations in myeloid cells can lead to myeloid leukemias, a group of cancers characterized by the uncontrolled proliferation of abnormal myeloid cells.

Flow cytometry is a powerful technology that allows for the rapid, quantitative analysis of multiple characteristics of individual cells within a mixed population. It works by suspending cells in a stream of fluid and passing them through an electronic detection apparatus, allowing simultaneous multiparametric analysis of the physical and chemical characteristics of up to thousands of particles per second. 

The Power of Flow Cytometry in Myeloid Tissue Analysis

Flow cytometry has transformed our understanding of myeloid biology and disease through its ability to provide detailed information on cell size, granularity, and phenotype. It is particularly useful for detecting small populations of cells that may be indicative of disease. There are some examples of key findings in the field of Myeloid Tissue Characterization that were made possible through flow cytometry:

Acute Myeloid Leukemia (AML) Diagnosis and Monitoring: Flow cytometry has greatly improved the diagnosis and monitoring of AML. It has enabled the identification of abnormal myeloid progenitor cells, which suppress normal hematopoietic activity. For instance, a study performed flow cytometric immunophenotyping in bone marrow aspirate and/or peripheral blood samples from patients with AML, using a panel of monoclonal antibodies specific for acute leukemias. The immunophenotyping demonstrated a characteristic profile of AML with expression of CD13 and CD33 in all cases and CD34 and CD117 in most cases.

Identification of Myeloid Subsets: Flow cytometry has been instrumental in identifying specific myeloid subsets. For example, it has been used to identify common cells of the myeloid compartment including monocytes, macrophages, dendritic cells, granulocytes, and mast cells. Each cell type has a specific function in the generation and resolution of an immune response.

Here is a table summarizing the key characteristics and roles of various white blood cells and their associated cell surface markers:
 Cell Type Marker (CD)  Key Characteristics and Functions
 Monocytes CD14+  Can differentiate into macrophages or dendritic cells. CD14 acts as a co-receptor for bacterial lipopolysaccharides, playing a role in pathogen recognition and immune response activation.
 Macrophages CD68+ Large white blood cells involved in phagocytosis, bactericidal activity, and chemotaxis. CD68 is a heavily glycosylated glycoprotein highly expressed in macrophages.
 Dendritic Cells CD11c+ Antigen-presenting cells crucial for immune responses. CD11c (integrin alpha X) is a marker for dendritic cells, enhancing their phagocytosis capabilities in vitro.
 Granulocytes CD15+ Include neutrophils, eosinophils, and basophils. CD15 serves as a ligand for selectins and may be involved in cell adhesion.
 Mast Cells CD117+ Involved in immune responses to allergies and asthma. CD117 (a receptor tyrosine kinase) is essential for identifying mast cells and plays a role in mast cell neoplasms.
Table 2. An overview of different white blood cell types, their specific markers, and their roles in the immune system, which are vital for diagnosing and treating various immune-related conditions.
Myelodysplastic Syndrome Panel: The Myelodysplastic Syndrome (MDS) Panel is a set of tests used to diagnose and monitor MDS, a group of disorders caused by poorly formed or dysfunctional blood cells. The main advantage of using flow cytometry for Myelodysplastic Syndrome (MDS) lies in its ability to enhance the sensitivity and specificity of diagnosis. This technology can detect subtle aberrations in the differentiation and antigen expression of hematopoietic cells in the bone marrow, which are often not visible through conventional morphological assessments.

In the myelodysplastic syndrome panel, blasts are identified by CD45/side scatter gating strategy and by CD34 expression; promyelocytes are identified by bright CD13, CD33, and CD117 expression without CD34; granulocytes and precursors are defined by their variable expression of CD13 and CD16 according to their maturational stages.
CD45/side scatter gating strategy: This is a common method used in flow cytometry to identify different cell populations based on their physical and structural characteristics. CD45 is a protein that is widely expressed on all cells of the hematopoietic lineage except mature red blood cells and platelets. Side scatter measures the granularity or internal complexity of a cell. So, blasts (immature cells) are identified by their expression of CD45 and their side scatter properties.

CD34 expression: CD34 is a marker that is typically expressed on the surface of early hematopoietic stem cells and progenitor cells. In the context of the MDS panel, it’s used to identify blasts.

CD13, CD33, and CD117 expression: These are markers that are expressed on myeloid cells. In the MDS panel, bright expression of CD13, CD33, and CD117 without CD34 is used to identify promyelocytes.

Variable expression of CD13 and CD16: CD13 and CD16 are also markers expressed on myeloid cells. Their variable expression according to maturational stages helps define granulocytes and their precursors.

Intracellular Antigens Evaluation: Intracellular antigens evaluated routinely by flow cytometry include terminal deoxynucleotide transferase (TDT) and myeloperoxidase (MPO) in acute leukemia samples and immunoglobulin light chains in plasma cell disorders.


Sample Preparation: The first step in flow cytometry analysis of myeloid tissue is sample preparation. This involves the collection of the tissue sample, which could be blood, bone marrow, or other body fluids. The sample is then diluted with a buffer, such as phosphate-buffered saline (PBS), and prepared into a single-cell suspension. This is crucial as flow cytometry requires a suspension of individual cells to analyze. For solid tissues, disaggregation can be done either mechanically or enzymatically to produce single cells.

Staining Procedures: Once the single-cell suspension is prepared, the cells are stained with specific antibodies that bind to markers on the cell surface. These antibodies are usually fluorescently labeled, allowing the flow cytometer to detect and quantify them. The selection of antibodies depends on the specific myeloid cells being studied. For instance, a study by Liu et al. used a panel of antibodies including CD11b, CD172a, MHCII, CD11c, CD115, and others for the analysis of myeloid populations in mouse tissues.

Data Analysis: After staining, the cells are passed through the flow cytometer. The machine uses a laser to excite the fluorescent molecules on the antibodies, and the emitted light is detected and measured. The data is then analyzed using software that can identify cell populations based on the presence or absence of the markers. This allows for the identification and quantification of different myeloid cell types.

Selection of Appropriate Markers for Myeloid Cells: The selection of appropriate markers is crucial for the accurate identification of myeloid cells. Common markers used for myeloid cells include CD33, CD123, CD14, CD16, HLA-DR, CD11c, CD141, and CD1c. These markers are used to define specific cell populations for additional analysis in each immunophenotyping experiment. For instance, CD14, CD163, and CD68 can detect macrophages in human lung tumors, with CD163 being a macrophage-specific marker. It’s important to note that the selection of markers can vary depending on the specific research question and the type of myeloid cells being studied.

Challenges and Limitations

Flow cytometry is a powerful tool for myeloid tissue analysis, but it does come with its own set of challenges and limitations. Below is a table summarizing the challenges and limitations of flow cytometry in analyzing myeloid tissue, as well as potential solutions to overcome these challenges:
 Challenges  Details  Solutions
 Sample Quality Requires fresh samples, processed quickly. Storage issues can lead to apoptosis, affecting analysis specificity.  Process samples immediately after collection to maintain cell viability and analysis accuracy.
 Autofluorescence Myeloid cells may exhibit autofluorescence, reducing resolution of analysis.  Utilize advancements that capture the full emission spectrum to mitigate autofluorescence.
 Gating Strategy Optimized gating strategies might not be applicable across different organs, e.g., strategies for collagenase IV digestion.  Tailor gating strategies to specific organs or tissues to improve accuracy.
 Marker Selection Requires correct antibody panel for accurate immunophenotyping. Incorrect panels can lead to irrelevant data. Choose antibody panels based on the specific disease or cell type being studied.
Technological   Innovations Traditional flow cytometry faces limitations in marker detection.  Employ CyTOF and other advanced technologies to detect numerous markers simultaneously.
 AI-Aided Techniques Challenges in optimizing flow cytometry data analysis. Use AI to enhance the quality and efficiency of flow cytometry data analysis.


In closing, the role of flow cytometry in the study of myeloid tissue cannot be overstated. This technology has become a cornerstone in both research and clinical environments, providing invaluable insights into the complex world of myeloid biology.

Flow cytometry’s ability to analyze individual cells in a heterogeneous population allows for a detailed understanding of the cellular diversity within myeloid tissue. This is crucial in identifying the subtle changes that can lead to disease states, thereby aiding in early detection and diagnosis.

The continuous advancements in flow cytometry technology, such as the development of more sensitive detectors and the use of novel fluorescent probes, promise to further enhance our ability to characterize myeloid tissue. These advancements could lead to the discovery of new cellular subtypes and a better understanding of their roles in health and disease.

Moreover, the insights gained from flow cytometry are not just theoretical. They have practical implications in the development of therapeutic strategies. By understanding the cellular dynamics of myeloid tissue, researchers can design more targeted and effective treatments for diseases related to this tissue.
Furthermore, flow cytometry allows for the monitoring of patient responses to these treatments. By tracking changes in the cellular composition of myeloid tissue, clinicians can assess the effectiveness of a treatment strategy and make necessary adjustments to improve patient outcomes.

As we look to the future, it is clear that flow cytometry will continue to play a pivotal role in biomedical research. Its ability to provide a detailed analysis of complex cellular systems makes it an indispensable tool in the ongoing quest to understand and treat diseases related to myeloid tissue.

In conclusion, the power of flow cytometry in characterizing myeloid tissue is undeniable. Its contributions to our understanding of myeloid biology and the pathogenesis of related diseases are immense and will continue to grow as the technology evolves. The future of myeloid tissue research is bright, thanks to the power of flow cytometry.

This entry was posted in Application and Technique Notes