K1-induced Lyn hyperphosphorylation and in vitro Lyn kinase activity in BJAB-K1 cells. Hyperphosphorylation and in vitro kinase activity of Lyn tyrosine kinase in BJAB-K1, BJAB-K1m, and BJAB-XS human B-lymphoma cells in the presence and absence of the Src protein tyrosine kinase inhibitor PP2 were determined as described in “Materials and methods.” Compared with BJAB-XS cells, the differences in Lyn kinase activity were significant in BJAB-K1m cells (^*P = .007) and BJAB-K1 (^*P = .01) cells.