Altered configuration of Gc on the plasma membrane of transformed and malignant human B lymphocytes

Normal human peripheral blood B cells exhibit strong membrane fluorescence for Gc (vitamin D-binding protein), and this protein can form a close spatial relationship with integral membrane immunoglobulin (mIg) with evidence of codistribution in the lipid bilayer. In contrast, fluorescence for both Gc and mIg has been found in this study to be weak or absent in several B lymphoblastoid cell lines and in chronic lymphocytic leukemia B cells. Moreover, the comobility of these components, where detectable, was also impaired. In abnormal B cells, the intensity of membrane fluorescence for Gc was substantially increased after crosslinking of mIg with antibody, and the latter was also associated with increased specific radioiodination of Gc by lactoperioxidase. These results indicate that Gc can apparently become displaced under certain circumstances within or through the lipid bilayer. The altered content or membrane topography of Gc in such abnormal B cells might be associated with impaired expression and mobility of mIg.