blood_and_immune_upper_slim has_not_completed lacks_plasma_membrane_part has plasma membrane part develops from immature B cell Immature B cells are also reportedly CD5-positive, CD10-positive, CD19-positive, CD20-positive, CD21-positive, CD22-positive, CD24-positive, CD25-negative, CD27-negative, CD34-negative, CD38-positive, CD40-positive, CD43-negative, CD45-positive, CD48-positive, CD53-positive, CD79a-positive, CD80-negative, CD81-positive, CD86-negative, CD95-negative, CD127-negative, CD138-negative, CD185-positive, CD196-positive, MHCII/HLA-DR-positive, RAG-positive, TdT-negative, Vpre-B-negative, and preBCR-negative. Transcription factors expressed: Pax5-positive. An immature B cell is a B cell that has the phenotype surface IgM-positive and surface IgD-negative, and have not undergone class immunoglobulin class switching or peripheral encounter with antigen and activation. immature B lymphocyte immature B-cell ZFA:0009343 https://cellxgene.cziscience.com/cellguide/CL_0000816 Immature B cells, also known as Hardy fraction E, represent an intermediate stage in B cell development. By this stage, the B cell precursors have undergone both heavy and light chain rearrangement, resulting in a diverse pool of B cell receptors (BCR). At this stage, the immature B cells undergo a stringent selection process to maintain B cell central tolerance. If an immature B cell is found to express self-reactive BCR, it can undergo receptor editing, in which rearrangement of its light chain genes is reinitiated, in an attempt to create a new, non-self-reactive BCR. If this editing process is unsuccessful and the BCR remains self-reactive, the cell can then be forced to undergo apoptosis, a process termed clonal deletion, thus preventing the production of auto-reactive, potentially harmful B cells. If the BCR recognizes self-antigen with low affinity, it may become anergic or unresponsive. Immature B cells that successfully pass these selection processes are then released from the bone marrow as transitional B cells and will complete their maturation process in secondary lymphoid organs. (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.) immature B-lymphocyte newly formed B cell small pre-B-II cell B cell, CD19-positive isotype switching IgD immunoglobulin complex IgM immunoglobulin complex Homo sapiens membrane-spanning 4-domains subfamily A member 1