Idiotype-immune serum induces tyrosine phosphorylation specifically in tumor B cells.

(A) Detection of tyrosine phosphorylation in tumor cells by Western blotting. Tumor cells from patient D31 were incubated with the indicated sera and then lysed. Solubilized proteins were separated by SDS-PAGE and transferred to nitrocellulose. The blot was stained with antiphosphotyrosine antibody 4G10. (B) Detection of tyrosine phosphorylation in tumor cells by flow cytometry. Tumor cells from patient D31 were treated with the indicated sera, permeabilized, and stained with antibody 4G10 coupled to FITC. Phosphotyrosine content was then quantitated in aliquots of cells counterstained with either phycoerythrin-labeled anti-CD20 or anti-CD3.