Immunohistochemical staining was performed using an indirect immunoperoxidase detection protocol (Vectastain Elite kit; Vector Laboratories) following treatment of sections with hyaluronidase to improve antibody penetration. Optimal antibody concentrations were determined by titration on select samples before analysis of the full experimental set. Staining was shown to be specific in control experiments in which either the primary antibody was preincubated with a 50-fold molar excess of immunizing peptide before being applied to the section (anti-TGF-β2, anti-TGF-β3), or the section was stained with an equivalent concentration of nonimmune rabbit immunoglobulin (anti-TGF-β1-LC, anti-TGF-β1-CC, and anti-LTBP). In analysis of the full experimental set, for any given antibody all sections were stained at the same time so as to be directly comparable, and a normal mouse embryo section was included as a positive control. A normal rabbit immunoglobulin control was also run for the whole set.