Characterization of tumor infiltrating T cells in low-grade MALT-type lymphomas, using multicolor FACS analysis of freshly isolated tumor cell suspensions. A: Summary of the percentage of B and T cells in tumor tissues (1–10, low-grade MALT-type lymphomas; 11, follicular gastritis, H. pylori-associated). B: Characteristic FACS histograms of TITLs of low-grade MALT-type lymphoma (no. 5) with high expression of CD69 and CD28 (solid line, isotype control; dashed lines, CD69 and CD28) of TITLs. C: Summary of FACS data of TITLs mean fluorescence intensity (MFI) of CD69 and CD28 expression as compared with T cells from PBLs of the same patients.