Tyrosine phosphorylation is required for ligand-induced internalization of the antigen receptor on B lymphocytes

The importance of tyrosine phosphorylation during ligand-induced internalization of membrane immunoglobulin (mIg) and its critical role for activating B cells as antigen presenting cells were investigated. Two tyrosine phosphorylation specific inhibitors inhibited mIg modulation on the cell surface and suppressed ligand-induced receptor internalization. These findings indicated that tyrosine phosphorylation in the B cells occured as a consequence of crosslinking mIg and was needed for internalization of mIg-ligand complexes. The results supported the essential role of tyrosine phosphorylation in the function of B lymphocytes.