Table 1.

Schematic illustration of the experimental design. Acute inflammatory challenges include IP E.coli, IP LPS, IA E.coli and IA LPS injections. Mice in the UP group received IP PBS injections for 3 days followed by an acute inflammatory challenge on day 4. Mice in the EU groups received increasing doses of IP E.coli injections for 3 days followed by an acute inflammatory challenge on day 4. Mice in the Ctrl group received 4 days of IP PBS injections. Mice in the EU-only group received euflammation induction for 3 days only. For circulating cytokine ELISA, brain and spleen cytokine qRT-PCR, IHC labeling of c-fos and COX-2, mice were sacrificed at 3 hrs after the IP immune challenges or 6 hrs after the IA immune challenges. For spleen pathogen recognition receptor qRT-PCR and IHC labeling of Iba-1, mice were sacrificed at 24 hrs after the last injection.

Treatment group		Euflammation induction (IP)			Acute inflammation	Time point for sacrifice
		Day 1	Day 2	Day 3	Day 4		Day 5
IP E.coli	UP	PBS	PBS	PBS	IP E.coli 100×107	Sac 3 hrs post injection	Or Sac 24 hrs post injection for IHC of Iba-1
	EU	E.coli 2×107	E.coli 25×107	E.coli 100×107	IP E.coli 100×107
IP LPS	UP	PBS	PBS	PBS	IP LPS
	EU	E.coli 2×107	E.coli 25×107	E.coli 100×107	IP LPS
IA E.coli	UP	PBS	PBS	PBS	IA E.coli 100×107	Sac 6 hrs post injection
	EU	E.coli 2×107	E.coli 25×107	E.coli 100×107	IA E.coli 100×107
IA LPS	UP	PBS	PBS	PBS	IA LPS
	EU	E.coli 2×107	E.coli 25×107	E.coli 100×107	IA LPS
CTRL		PBS	PBS	PBS	IP PBS	Sac 3 hrs post injection
EU-only		E.coli 2×107	E.coli 25×107	E.coli 100×107	Sac 24 hrs post injection