CD43 Human

What is the molecular structure of human CD43?

CD43 is a large mucin-like sialoglycoprotein with an extracellular domain extensively modified by O-linked glycans. This domain extends approximately 45 nm from the leukocyte surface, making it one of the most extended cell-surface molecules . It is a type I transmembrane protein with a molecular weight of approximately 115 kDa in its lower molecular mass glycoform present on resting lymphocytes . The protein contains a cytoplasmic tripeptide sequence KRR that engages with ezrin-radixin-moiesin cytoskeletal proteins, which is important for its signaling functions .

What are the expression patterns of CD43 across human cell types?

CD43 is abundantly expressed on most cells of hematopoietic lineage . It is prominently found on T cells where it functions as a co-stimulatory molecule by transducing activation signals through its cytoplasmic domain . CD43 is detected on various hematopoietic progenitors before they express CD45, making it an earlier marker of hematopoietic commitment . Different glycoforms of CD43 are expressed on different cell populations, with the 115 kDa glycoform predominantly found on resting T and NK cells .

How does CD43 expression change during cell activation and differentiation?

CD43 expression levels change during T cell activation, with memory T cells showing elevated surface CD43 expression compared to naive cells . During hematopoietic development, CD43 appears on early progenitors committed to hematopoietic development before CD45 expression . The acquisition of CD45 expression by CD34+CD43+CD45- cells is associated with progressive myeloid commitment and decreased B-lymphoid potential, indicating that CD43 expression patterns change during lineage commitment .

What isolation techniques are most effective for studying CD43+ cell populations?

Several effective methods exist for isolating CD43+ cells:

• Magnetic Cell Sorting (MACS):

  • Direct isolation using CD43 microbeads

  • Indirect isolation using CD43-FITC mAb followed by anti-FITC microbeads

• Fluorescence-Activated Cell Sorting (FACS):

  • CD43+ cells can be enriched by MACS and then further separated into subpopulations (CD43+CD41a/CD235a+CD45-, CD43+CD41a/CD235a-CD45-, CD43+CD41a/CD235a-CD45+) using FACS

For optimal results, isolating CD43+ cells from hESC/OP9 cocultures by positive MACS selection achieves purities exceeding 95%, while FACS sorting can achieve >98% purity for specific CD43+ subsets .

What antibodies and detection methods are recommended for CD43 research?

Several antibodies have been used successfully in CD43 research:

• HSCA-2 mAb: Recognizes a sialic acid-dependent epitope on the low molecular mass glycoform of CD43 expressed in resting T and NK cells

• Anti-CD43 antibodies for flow cytometry analysis (often used with markers like CD34, CD45, CD41a, and CD235a to identify specific hematopoietic subpopulations)

• Anti-CD43 antibody coating for cell immobilization in culture systems

For multi-parameter analysis, common antibody combinations include:

• CD19/CD23/CD43 for B cell subpopulations

• CD34/CD43/CD45/lineage markers for hematopoietic progenitors

How can CD43 be utilized for cell immobilization in experimental systems?

Anti-CD43 antibody coating reduces the motility of hematopoietic stem and progenitor cells (HSPCs) in a concentration-dependent manner . This approach enables:

• 2D colony formation without cell mixing in liquid cultures

• Maintenance of cell positions during media exchange

• Increased throughput of time-lapse imaging

• Continuous analysis of suspension cells in dynamic culture conditions

This technique substantially simplifies tracking individual cell identities over time, which is crucial for studying cellular behavior at the single-cell level. The concentration of anti-CD43 antibody coating affects cell proliferation, with higher concentrations reducing mouse HSPC proliferation, though no relevant effects on cell survival or differentiation were observed at moderate concentrations .

How does CD43 serve as a marker for hematopoietic lineage commitment?

CD43 is a critical marker that identifies early progenitors committed to hematopoietic development . Key findings include:

• CD43 expression precedes CD45 expression on emerging hematopoietic progenitors

• CD43 reliably separates hematopoietic CD34+ cells from CD34+CD43-CD31+KDR+ endothelial and CD34+CD43-CD31-KDR- mesenchymal cells

• CD43 is detected on all types of emerging clonogenic progenitors

This makes CD43 an excellent marker for identifying committed hematopoietic cells in both adult and embryonic systems .

What are the phenotypic characteristics of different CD43+ hematopoietic subpopulations?

This phenotypic characterization allows precise identification and isolation of specific hematopoietic progenitor populations at different stages of development .

What is the relationship between CD43 expression and hematopoietic stem cell differentiation potential?

The acquisition of CD45 expression by CD34+CD43+CD45-Lin- cells is associated with progressive myeloid commitment and decreased B-lymphoid potential . The earliest CD43+ hematopoietic progenitors (CD34+CD43+CD45-) display features of endothelial-like precursors, expressing endothelial proteins and transcription factors typical of definitive hematopoiesis. As these cells acquire CD45 expression, they progressively lose endothelial characteristics and become increasingly committed to myeloid lineages .

What are the signaling mechanisms associated with CD43 in human immune cells?

CD43 functions as a co-stimulatory molecule in T cells by transducing activation signals through its cytoplasmic domain . The cytoplasmic tripeptide sequence KRR of CD43 engages with ezrin-radixin-moiesin cytoskeletal proteins to mediate signaling functions . This interaction is important in various immune responses, including acute inflammatory responses like myocarditis . CD43 signaling contributes to downstream T cell gene regulation and modulates cell function, ultimately influencing T cell activation, proliferation, and effector functions .

How does CD43 contribute to inflammatory responses and disease pathogenesis?

CD43 plays significant roles in inflammatory conditions:

• In Chagas' disease (caused by Trypanosoma cruzi), CD43 modulates cardiac inflammation and affects host resistance

• CD43-deficient mice show increased resistance to T. cruzi infection due to:

  • Enhanced cytotoxicity of antigen-specific CD8+ T cells

  • Reduced inflammatory infiltration in cardiac tissue

  • Lower cardiomyocyte damage

The induction of acute myocarditis involves CD43's cytoplasmic tripeptide sequence KRR engagement with cytoskeletal proteins, contributing to inflammatory cell recruitment and tissue damage .

What role does CD43 play in regulatory B cell functions?

CD23+CD43+ B cells appear to have immunoregulatory properties . When human mesenchymal stem cells (hMSCs) are cocultured with B cells, they can induce a regulatory CD23+CD43+ B cell population that suppresses T cell responses . These CD23+CD43+ B cells mediate their suppressive effects at least partially through IL-10 production, as blocking IL-10 with anti-IL-10 mAb largely rescues IFN-γ and TNF-α production . This suggests CD43 expression on specific B cell subsets correlates with regulatory functions important for immune homeostasis.

How can CD43-targeting approaches be utilized for therapeutic applications?

Several CD43-targeting approaches show therapeutic potential:

• Immobilization strategies: Anti-CD43 antibody coating provides a method for cell immobilization in culture systems, enabling better tracking and manipulation of hematopoietic cells for potential cell therapy applications

• Regulatory cell induction: The identification of CD23+CD43+ regulatory B cells induced by mesenchymal stem cells offers possibilities for developing immunomodulatory therapies for inflammatory and autoimmune conditions

• T cell stimulation: The HSCA-2 mAb that recognizes CD43 markedly increases the proliferative responsiveness of CD4+ memory T cells to recall antigens, suggesting potential applications in enhancing specific immune responses

What are emerging research directions in CD43 biology?

Emerging research areas include:

• Hematopoietic development modeling: Using CD43 as a marker to track hematopoietic commitment in human embryonic stem cell differentiation systems provides new opportunities to model human developmental hematopoiesis

• Single-cell analysis: Anti-CD43 antibody coating for reducing cell motility enables continuous monitoring of individual hematopoietic cells, facilitating single-cell analysis of dynamic behaviors and lineage relationships

• Regulatory immune networks: Investigation of CD23+CD43+ B cells in immune regulation may reveal new networks controlling inflammatory responses and tolerance induction

How can CD43 expression patterns be leveraged for improved cell isolation in research and clinical applications?

CD43 expression patterns can be leveraged to:

• Isolate early hematopoietic progenitors before they express CD45, enabling more comprehensive studies of early hematopoietic development

• Distinguish hematopoietic cells from endothelial and mesenchymal populations in mixed cultures, improving purity in cell isolation protocols

• Identify specific functional subsets of B cells with regulatory properties, potentially useful for immunotherapy approaches

• Select cells at precisely defined developmental stages based on combinations of CD43 with other markers (CD34, CD45, CD41a, CD235a), enabling investigation of stage-specific cellular properties