preBcell

The pre-B cell stage represents a crucial developmental phase for B lymphocytes in the bone marrow. This stage is characterized by the successful expression of the pre-B cell receptor (pre-BCR) on the cell surface. The pre-BCR is a signaling complex composed of a functional mu heavy chain paired with a surrogate light chain. Its assembly and expression are critical for survival and progression to the next developmental stage.

Prior to reaching the pre-B cell stage, progenitor B cells undergo V(D)J recombination of the immunoglobulin heavy chain genes. Successful rearrangement leads to the production of a mu heavy chain. If this mu heavy chain is unable to pair with a surrogate light chain, the cell undergoes apoptosis. Upon successful formation of the pre-BCR, the cell receives survival signals and enters a phase of rapid proliferation, known as expansion. This expansion amplifies the population of cells that have successfully initiated heavy chain rearrangement.

Following proliferation, the pre-B cell begins to rearrange its immunoglobulin light chain genes. Once a functional light chain is successfully rearranged and pairs with the existing mu heavy chain to form a complete immunoglobulin M (IgM) molecule, the cell transitions to the immature B cell stage. The pre-B cell stage is therefore a checkpoint ensuring the integrity of heavy chain gene rearrangement and the capacity for light chain recombination.