FIG 5.

Greater frequencies of cells in the MLN of neonates potentially contribute to enhanced proinflammatory gene expression after Y. enterocolitica infection. (A) MLN cells from uninfected neonates or adults were either untreated or stimulated in vitro for 16 h with 100 ng/ml LPS, and the frequency of IL-6-expressing cells was evaluated by ELISPOT. *, P ≤ 0.05. (B) Neonatal and adult MLN were harvested 48 h postinfection with 2 × 10⁸ CFU of the Y. enterocolitica ΔyopP strain and stained by immunohistochemistry for TNF-α. TNF-α is indicated by Alexa Fluor 488 (green), and Hoechst was used as a nuclear counterstain (blue). Representative images are shown at ×63 magnification.