Age-dependent IL-12 responses. MLN and spleen cells from 6- to 14-day-old neonates (closed circles), 20-day-old lambs (closed diamonds) and adults (open squares) were cultured in vitro for 48 h, with 1 μM CpG-2006 or 1 μM Ctl-ODN. At the end of the culture period, supernatants were harvested and ELISA carried out to assay IL-12 secreted by MLN cells (A) or spleen cells (B). Medians are shown for each stimulus. * p ≤ 0.01; ** p ≤ 0.001; *** p ≤ 0.0005.