Analysis of Lyn and Syk proteins and Lyn kinase in escapees. All lysates were prepared from splenocytes recovered from BCL₁ tumor bearing nonimmune mice and BCL₁ escapees. The presence of Syk (top) and Lyn (center) were determined by immunoblotting. Lyn tyrosine kinase was immunoprecipitated from separate samples and immune complex kinase assay performed (see the Materials and Methods) (bottom). Lane 1, BCL₁ ; lane 2, escapee no. 1; lane 3, escapee no. 3; lane 4, escapee no. 6; lane 5, escapee no. 9; and lane 6, escapee no. 10.