Morphological and other changes in untreated CCH, CCH treated with 5-fluorouracil (5-FU) or infected with M. synoviae. CCH were seeded onto cover slides and incubated overnight. Cells were then treated with 5-FU or infected with M. synoviae and incubated for 24 h, 48 h and 72 h followed by fixation in an acetone-methanol mixture, blocking and labeling with mouse antibodies to chicken CD44. Alexafluor-488 goat antibodies to mouse IgG were used as secondary antibodies and nuclei were labeled with propidium iodide. Nuclear condensation and formation of blebs containing nuclear material are indicated by arrows.