CD Antigens

Key Biological Properties: CD34 is a heavily sialylated, O-linked glycosylated protein with some N-linked glycosylation sites . It functions primarily as an adhesion molecule, mediating cell-cell and cell-matrix interactions .

Expression Patterns: CD34 is predominantly expressed on hematopoietic stem and progenitor cells, vascular endothelial cells, certain fibroblasts, and some types of bone marrow stromal cells . It is also found on muscle stem cells and endothelial cells .

Tissue Distribution: CD34+ cells are typically found in the umbilical cord, bone marrow, and endothelial cells of blood vessels . They are also present in soft tissue tumors like dermatofibrosarcoma protuberans (DFSP), gastrointestinal stromal tumors (GIST), and solitary fibrous tumors (SFT) .

Primary Biological Functions: CD34 functions as an adhesion molecule, facilitating the attachment of stem cells to the extracellular matrix in bone marrow and other tissues . It also plays a role in cell migration and morphogenesis .

Role in Immune Responses: CD34 is involved in the trafficking and migration of hematopoietic cells, including T cells . It is required for T cells to enter lymph nodes, where it binds to L-selectin on T cells .

Pathogen Recognition: While CD34’s role in pathogen recognition is not well-documented, its involvement in immune cell trafficking suggests it may play a role in immune surveillance and response .

Mechanisms with Other Molecules and Cells: CD34 interacts with various molecules, including L-selectin on T cells, facilitating their entry into lymph nodes . It also mediates the attachment of hematopoietic stem cells to bone marrow extracellular matrix or stromal cells .

Binding Partners: CD34 binds to L-selectin on T cells and potentially other ligands on endothelial cells . It may also interact with other members of the sialomucin family, such as podocalyxin and endoglycan .

Downstream Signaling Cascades: The exact downstream signaling pathways of CD34 are not well understood. However, its role in cell adhesion and migration suggests it may be involved in signaling pathways related to cytoskeletal rearrangement and cell motility .

Transcriptional Regulation: The expression of CD34 is regulated at the transcriptional level by various factors, including cytokines and growth factors .

Post-Translational Modifications: CD34 undergoes extensive post-translational modifications, including sialylation and glycosylation, which are crucial for its function as an adhesion molecule .

Biomedical Research: CD34 is widely used as a marker to identify and isolate hematopoietic stem cells for research and clinical applications . It is also used to study tumor vasculature and stem cell differentiation .

Diagnostic Tools: CD34 antibodies are used in diagnostic immunohistochemistry to identify and classify various tumors, including DFSP, GIST, and SFT .

Therapeutic Strategies: CD34+ cells are used in bone marrow transplantation to treat various hematological disorders . The isolation and enrichment of CD34+ cells improve the success rates of these transplants .

Development: CD34 is expressed on hematopoietic stem cells during early development and plays a crucial role in the formation of the hematopoietic system .

Aging: The expression of CD34 decreases with age, which may contribute to the decline in hematopoietic stem cell function observed in older individuals .

Disease: CD34 expression is altered in various diseases, including leukemia and other hematological disorders . It is also used as a marker to identify cancer stem cells in certain tumors .