Immunofluorescence analysis was performed as described earlier (4749). Briefly, coverslips containing 100 to 200 cells/mm2 were fixed with 4% paraformaldehyde followed by treatment with cold ethanol and two rinses in PBS. Samples were blocked with 3% bovine serum albumin (BSA) in PBS–Tween 20 (PBST) for 30 min and incubated in PBST containing 1% BSA and anti–IL-11 or anti-CD3. After three washes in PBST (15 min each), slides were further incubated with Cy2 (Jackson ImmunoResearch Laboratories Inc.). For negative controls, a set of culture slides was incubated under similar conditions without the primary antibodies. The samples were mounted and observed under an Olympus IX81 fluorescence microscope. Counting analysis was performed using Olympus MicroSuite V software with the help of a touch counting module.