Why does each B cell produce only one specific antibody despite the body’s vast antibody diversity?

Each B cell produces only one specific antibody because of the unique genetic rearrangement that occurs during its maturation. While the body possesses the capacity to generate millions of different antibodies, this diversity is not encoded by millions of separate genes. Instead, it arises from a limited number of immunoglobulin gene segments—specifically the variable (V), joining (J), and other segments—that rearrange and assort randomly in each individual B-lymphocyte precursor cell.1

In a mature B cell, only one specific combination of these segments is incorporated into the sequence that codes for antibody production. Once this rearrangement is finalized, the B cell is committed to producing antibodies that recognize a single, specific antigen or receptor site. When a B cell encounters its corresponding antigen, it undergoes activation and clonal expansion, creating a population of cells that all share that same original specificity. Therefore, while the B cell population as a whole provides the body with vast antibody diversity, each individual B cell remains restricted to producing a single, specific type of antibody.123