Altered distribution of marker proteins. Frozen sections of spleens of newborn wild-type (A, B, C, and D) and KO mice (E, F, G, and H) stained with antibodies to type-IV collagen (A and E), laminin (B and F), c-kit (C and G), and vimentin (D and H). Arrowheads in (A) indicate a fibrous structure. Scale bars: 100 μm.