Immunohistochemical analysis of thymus from ADA-deficient mice after GT with long- and short-term ERT. Perfused thymi were fixed, sectioned, and stained with antihuman ADA antibody (N-19; Santa Cruz Biotechnology) that was specific to human ADA and did not cross-react with murine ADA. Cells containing immune-reactive protein are stained brown. Micrographs of stained sections were made with an Olympus BX40 Microscope (Olympus America Inc) and an Olympus DP11 Camera (Olympus America Inc) All micrographs were made at room temperature, without the use of imaging medium, fluorochromes, or acquisition software. Magnification: (optical 10) total magnification ×200. (A) Thymi from 2 different normal control (Ada+/+) mice, ×200 + 1mERT, mice and 200−NoERT mice at 4 weeks. (B) Thymi from 2 different 200 + ERT mice, 200−NoERT mice, and 200 + 1mERT mice at 10 weeks.