B lymphocytes originate from hematopoietic stem cells in the bone marrow and undergo a series of tightly regulated differentiation events that enable them to produce highly specific and effective antibody responses. One of the most important early differentiation events is V(D)J recombination, which occurs during antigen-independent development in the bone marrow. In this process, the immunoglobulin heavy and light chain genes are assembled from variable (V), diversity (D), and joining (J) gene segments through the action of recombination-activating genes RAG-1 and RAG-2. Random selection and joining of these gene segments, along with junctional diversity generated by nucleotide addition or deletion, produces a vast repertoire of unique B-cell receptors. This event ensures that each mature B cell expresses a single antigen specificity, forming the molecular basis of humoral immune diversity. Successful rearrangement leads to expression of surface IgM and later IgD, marking the transition