Introduction: Lymphotoxin (LT) normally stimulates LTßR in Peyer’s patches (PP) to activate NF-?B via the non-canonical pathway to produce adhesion molecules (MAdCAM-1), cytokines, and chemokines critical to mucosal immune cell entry & function. Without LTßR, mice lack PP & lymph nodes and have less expression of MAdCAM-1, CCL-20, CCL25, CXCL13 and lower IL-4, IL-10 & IgA. PN decreases LTßR, MAdCAM-1 & these chemokines in PP and also lowers gut IgA compared to chow. The normal LT/ LTßR interaction activates the non-canonical NF-?B pathway to process the p100/RelB precursor and yield p52/RelB. Through an inflammatory canonical path, TNFa, IL-1ß, & bacterial products (via TLR) stimulate NF-?B producing p65/p50 and c-Rel/p50 heterodimers. Inflammation increases gut IgA levels. This work determines effects of PN, exogenous LTßR stimulation & exogenous LTßR blockade on both NF-?B activation pathways.

Methods: Expt 1: Phosphorylated canonical (p50& p65) and non-canonical (p52 & Rel B) NF-?B proteins in PP were analyzed by TransAM NF-?B Family kit after 5 days of chow (n=19) or PN (n=16). Expt 2: For 2 days, mice received chow (n=13), PN+ 5 µg of an LTßR-stimulating antibody BID, i.v(PN-LTßR,n=17)) or PN + control antibody (PN-control n=18) with Phosphorylated NF-?B proteins in PP analyzed as Expt 1. Expt 3: For 3 days mice received Chow + control Ig (Chow n=9), Chow + blocking LTßR-Ig fusion protein (100 ?g i.v.) (Chow- anti LTßR. N=10), or PN + control Ig (PN, n=8) to analyze Phosphorylated NF-?B in PP as Expt 1.

Results: PN significantly reduced all NF-?B proteins in PP compared with chow (p<0.01 for all except Rel B(p<0.05)) . LTßR stimulation with PN increased p50 (p<0.01), p52 (p<0.01), and Rel B(p<0.01) in PP vs PN alone with no differences vs chow in p65, p52 and Rel B; only p50(p<0.01) remained depressed in PN-LTßR vs chow. LTßR blockade of chow mice reduced non-canonical pathway (p52; p<0.01) and Rel B; p<0.01)) to PN levels but not the inflammatory path (p50 and p65).

Conclusion: Lack of enteral stimulation during PN decreases canonical and non-canonical NF-?B pathways in PP. LTßR stimulation during PN completely restores PP non-canonical NF-?B activity & partly restores the canonical pathway. LTßR blockade decreases non-canonical PP NF-?B activity but not canonical.

Table 1. NF-?B Activities in PP (Mean OD±SD)

	p50	p65	p52	Rel B
Expt 1 Chow	.19±.13	.09±.04	.67±.33	.08±.03
PN	.08 ±.05 a	.04± .02 a	.25±.2 a	.06±.02*
Expt 2 Chow	.58±.07	.26±.06	.16±.05	11±.03
PN-Control	.34±.13 a	.21±.05*	.13±.05*	.07±.04*
PN-LTßR	.47±.17*b	.25±.06	.17±.03b	.13±.08b
Expt 3 Chow	.33±.03	.39±.09	.78±.26	.16±.04
PN	.26±.07 a	.32±.06*	.60±.11*	.09±.04 a
Chow anti- LTßR	.32±.04 b	.35±.07	.51±.16 a	.11±.03a

*p<0.05 vs chow; a p<0.01 vs chow; b p<0.01 vs PN .