TSH staining in the mucosa is associated with areas of IL-7 staining. Panel A: under filtration that excluded red illumination of IL-7 staining, TSH staining was evident in both lower and upper crypt areas. Panel B: under filtration that excluded green illumination of TSH staining, IL-7 staining was localized only in upper crypt areas. Panel C: simultaneous examination of both regions confirmed those staining patterns, demonstrating clear evidence for simultaneous synthesis of TSH and IL-7 is some crypt areas, in particular those most distal to the muscularis. Results are representative of three mice. Magnification: Panel A–C, 400x.