precursor B cell pre-B-I cell Human pre-B-I cells are reportedly CD10-positive, CD19-positive, CD22-positive, CD38-positive, CD45-low, CD79a-positive, CD127-negative, pre-BCR-negative, IgM-negative, IgD-negative, and Tdt-positive. Transcription factors expressed: Pax5-positive. The pre-B-I cell, also known as an early pre-B cell, is an integral step in the B cell development pathway in the bone marrow. These precursor B cells are characterized by expression of CD34 and surrogate immunoglobulin light chain (VpreB , Lambda 5 (mouse)/14.1 (human)) on the cell surface, as well as TdT, Rag1,and Rag2 intracellularly; they carry a D-JH DNA rearrangement, and lack expression of immunglobulin heavy chain protein. This cell type represents the stage subsequent to pro-B cells but precedes pre-B-II cells. At the pre-B-I cell stage, cells undergo VH to D-JH recombination. At this point, if the rearranged μ heavy chain can be produced and paired with a surrogate light chain, this can be expressed on the cell surface as the pre-B cell receptor (pre-BCR), forming the next stage of development, the pre-B-II cell. (This extended description was generated by ChatGPT and reviewed by the CellGuide team, who added references, and by the CL editors, who approved it for inclusion in CL. It may contain information that applies only to some subtypes and species, and so should not be considered definitional.) A pre-B-I cell is a precursor B cell that expresses CD34 and surrogate immunoglobulin light chain (VpreB , Lambda 5 (mouse)/14.1 (human)) on the cell surface, and TdT, Rag1,and Rag2 intracellularly. Cell type carries a D-JH DNA rearrangement, and lacks expression of immunglobulin heavy chain protein. https://cellxgene.cziscience.com/cellguide/CL_0000956 pre-BI cell pro-B cell (Philadelphia nomenclature)