Defective apoptotic cell uptake by PSR-deficient macrophages without induction of inflammatory cytokines. (A,E) The E13.5 liver sections (A) and E16.5 thymus sections (E) of PSR^+/- and PSR^-/- littermates were stained with TUNEL (green) and anti-F4/80 antibody (red). Typical examples of phagocytosed or unphagocytosed apoptotic cells are shown by the arrows or arrowheads, respectively. The white bar indicates 100 μm. (B,F) The percentage of unphagocy tosed apoptotic cells in E13.5 liver sections (B) or E16.5 thymus sections (F) is compared between PSR^+/- (▨, n = 640 for liver sections and n = 106 for thymus sections) and PSR^-/- (▪, n = 176 for liver sections and n = 44 for thymus sections) littermates. (C,G) The number of F4/80⁺ macro phages per 100 000 μm² of E13.5 liver sections (C) or E16.5 thymus sections (G) is compared between PSR^+/- (▨) and PSR^-/- (▪) littermates. F4/80⁺ cells with more than 60 μm² of surface area were counted. (D,H) The total number of TUNEL-positive cells per 100 000 μm² of E13.5 liver sections (D) or E16.5 thymus sections (H) is compared between PSR^+/- (▨) and PSR^-/- (▪) littermates. (I) The E18.5 thymuses of PSR^+/- and PSR^-/- littermates were analyzed for the expression of TNF-α, IFN-β, IFN-γ, and TGF-β by RT-PCR. The primers used to amplify IFN-β were described elsewhere.¹⁴  For amplification of TNF-α, IFN-γ, and TGF-β, sets of specific primers were obtained from Toyobo (Osaka, Japan). The gene encoding hypoxanthine phosphoribosyl transferase (HPRT) used as a control was amplified with the following primers: 5′-CACAGGACTAGAACACCTGC-3′ and 5′-GCTGGTGAAAAGGACCTCT-3′. Amplification increases by 3 cycles, from the left to the right, starting at 22 cycles for TGF-β and HPRT, or at 25 cycles for TNF-α, IFN-β,and IFN-γ. Error bars (B-D, F-H) indicate standard deviation.