The age of immune effectors determines the outcome of TLR3 engagement. (A) Bulk splenocytes and BM cells from healthy Eμ-Ret mice of varying ages were exposed to indicated ligands and viable LIC recovery measured after 48 hours. Results are pooled from at least 4 individual experiments and analyzed using Dunnett multiple comparison test. (B) Purified LIC from neonatal and adult Eμ-Ret mice were incubated alone or with splenocytes from 2-wk-old (neonate) or 4-wk-old (adult) BALB/c mice. Cultures were treated with Poly(A:U), and viable cell recovery was measured after 48 hours and compared with that of unstimulated controls. Results are pooled from at least 3 individual experiments and analyzed using Dunnett multiple comparison test. (C) Four human B-ALL samples were incubated with cord or adult PBMCs. Cultures were treated with or without Poly(A:U), and viable cell recovery was measured using CountBright beads after 48 hours and analyzed using unpaired t test. For all graphs, bars represent mean ± SD; ∗P < .05; ∗∗P < .01; ∗∗∗P < .001; ∗∗∗∗P < .0001; ns. wk, week.