Abstract
CD38 is a multifunctional cell surface receptor expressed on multiple cell lineages of hematopoietic origin with high levels of expression on human plasma cells. Previously, we isolated the monoclonal variable lymphocyte receptor B (VLRB) MM3 antibody from the evolutionarily distant sea lamprey, which recognized the CD38 ectoenzyme exclusively on human plasma cells in a manner that correlated with CD38 enzymatic activity. The plasma cell-specific binding of VLRB MM3 contrasts with the broad pattern of expression of CD38-determined conventional antibodies specific for this antigen. In an effort to facilitate the application of this unique reagent in combination with conventional antibody panels, we explored a strategy to generate VLRB MM3 tetramers. The resulting reagent maintained the threshold-based recognition of CD38. Increased sensitivity achieved with VLRB MM3 tetramers also showed preferential recognition of germinal center centroblasts over centrocytes. VLRB MM3 tetramers thus provided a unique and versatile single-step staining reagent for the detection of human CD38 that is readily incorporated into multi-color flow cytometry panels.
Highlights
CD38 is an ectoenzyme with nicotinamide adenine dinucleotide (NAD) hydrolase and NAD cyclase activity and is expressed on a variety of cells, including epithelial cells, skeletal and cardiac muscle fibers, and numerous hemopoietic cell lineages [1,2]
In order to investigate whether a similar approach was possible for the unique CD38 binding characteristics of variable lymphocyte receptor B (VLRB) MM3, we designed monomeric VLRB MM3 molecules of which the C-terminal characteristics of VLRB MM3, we designed monomeric VLRB MM3 molecules of which the C56 amino acids containing eight cysteine residues involved in disulfide bond formation for VLRB
Terminal 56 amino acids containing eight cysteine residues involved in disulfide bond formation for multimerization were replaced by sequences encoding the HA- and 6xHis epitope tags and the VLRB multimerization were replaced by sequences encoding the HA- and 6xHis epitope tags and the recognition sequence for the BirA biotin ligase
Summary
CD38 is an ectoenzyme with nicotinamide adenine dinucleotide (NAD) hydrolase and NAD cyclase activity and is expressed on a variety of cells, including epithelial cells, skeletal and cardiac muscle fibers, and numerous hemopoietic cell lineages [1,2]. Expression levels of CD38 on human B cells vary during B cell development and differentiation It is expressed on B lineage precursors in the bone marrow and following B cell activation on germinal center B cells, but it is expressed only at very low levels on naïve and memory B cells [7,8]. It is expressed at high levels on antibody-secreting plasma cells and plasmablasts, making it an immunotherapeutic target of monoclonal antibodies in multiple myeloma [9].
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