Focal expression of Irga6 in healthy mouse liver and kidney. (A) Irga6 is expressed focally in the liver and kidney. Paraffin sections of C57BL/6 healthy adult mice liver and kidney were probed for Irga6 protein (green). In liver the parenchyma, between the high expression foci, is stained uniformly with Irga6 as a result of transcription from the liver-specific Irga6 promoter . Two types of Irga6 focal expression in liver are depicted: a stained patch without an evident core (P) and a patch with a mononuclear cell core (cored patch, CP). Here and in (B) the microscope magnification is 200×; frames show enlargements. (B) T cells and macrophages/dendritic cells are present in the mononuclear cores of the liver and kidney patches. Wax sections of the livers and kidneys from adult C57BL/6 mice were stained for Irga6 (brown/red) and CD3 or F4/80 (blue). For Irga6 and CD3 double staining in liver, consecutive serial sections were analysed (numbered 1, 2, 3, 4). Arrows point to CD3 and F4/80 positive cells; frames show enlargements. (C) Irga6 focal expression is developmentally regulated. Wax sections through whole livers and kidneys from C57BL/6 newborn mice and mice, aged as indicated, were stained for Irga6. High expression foci were counted within multiple microscopic fields (see Methods section). Each value in the histogram represents the mean of 30 such counts for organs from two mice of each age (error bars indicate standard deviations).