Exogenous SAA selectively induces T_reg proliferation. (A top) Effects of recombinant SAA at different doses on T_reg and T_eff proliferation in suppression assays (n = 2). (Bottom) Representative FACS plots of CFSE staining to track proliferation of T_reg and T_eff in suppression assays. (B left) Frequency of T_reg out of total peritoneal CD4⁺ T cells collected 16 hours after intraperitoneal injection with endotoxin (n = 7), recombinant human SAA (rhSAA, n = 10), and human serum albumin (HSA, n = 1). Recombinant SAA and HSA were used at 30 μg per injection in 100 μL PBS. LPS were injected at concentration similar to the level detected in recombinant SAA solution (0.25 pg/mL). (Right) Representative FACS plots of T_reg frequency in peritoneal fluid. (C top) Percentages of proliferating T_eff and T_reg in peritoneal fluid after SAA injection. (Bottom) Representative FACS plots of percentages of proliferating T_eff and T_reg in peritoneal fluid. Unpaired 2-tailed t tests (B-C) were used for statistical analyses. Horizontal bars represented median values; bar graphs represented means and SEs where indicated throughout the figure.