Northern blot analysis. Tissue RNAs were extracted and analyzed for IFN-γ mRNA after electrophoresis through a formaldehyde-agarose gel as described in the Materials and Methods. (A) Lane 1, normal bone marrow; lane 2, transgenic bone marrow; lane 3, transgenic bone marrow; lane 4, normal thymus; lane 5, transgenic thymus; lane 6, transgenic thymus; lane 7, normal thymus; lane 8, normal spleen; lane 9, transgenic spleen. (B) Lane 1, normal thymic stromal cells; lane 2, transgenic thymic stromal cells; lane 3, normal thymocytes; lane 4, transgenic thymocytes.