An essential role for BLNK in human B cell development

The signal transduction events that control the progenitor B cell (pro-B ce ll) to precursor B cell (pre-B cell) transition have not been well delineat ed. In evaluating patients with absent B cells, a male with a homozygous sp lice defect in the cytoplasmic adapter protein BLNK (B cell Linker protein) was identified. Although this patient had normal numbers of pro-B cells, h e had no pre-B cells or mature B cells, indicating that BLNK plays a critic al role in orchestrating the pro-B cell to pre-B cell transition. The immun e system and overall growth and development were otherwise normal in this p atient, suggesting that BLNK function is highly specific.