Lymphotoxin-Independent Expression of TNF-Related Activation-Induced Cytokine by Stromal Cells in Cryptopatches, Isolated Lymphoid Follicles, and Peyer’s Patches

Abstract

Stromal cells play a crucial role in the organogenesis of lymphoid tissues. We previously identified VCAM-1+ stromal cells in cryptopatches (CP) and isolated lymphoid follicles (ILF) in the small intestine of C57BL/6 mice. Nonhemopoietic stromal cell networks in CP and ILF of adult mice also expressed FDC-M1, CD157 (BP-3), and TNF-related activation-induced cytokine (TRANCE). Individual stromal cells were heterogeneous in their expression of these markers, with not all stromal cells expressing the entire set of stromal cell markers. Expression of VCAM-1, FDC-M1, and CD157 on CP stromal cells was absent in alymphoplasia mice deficient in NF-κB-inducing kinase (NIK) and NIK knockout mice. Administration of lymphotoxin β receptor (LTβR)-Ig to wild-type mice on day 13 resulted in the absence of CP on day 20; delaying administration of LTβR-Ig until day 18 resulted in an 80% decrease in the number of CP on day 22 and diminished expression of VCAM-1, FDC-M1, and CD157 on the remaining CP. In sharp contrast, TRANCE expression by stromal cells was completely independent of NIK and LTβR. In addition, expression of TRANCE in ILF was concentrated just beneath the follicle-associated epithelium, a pattern of polarization that was also observed in Peyer’s patches. These findings suggest that TRANCE on stromal cells contributes to the differentiation and maintenance of organized lymphoid aggregates in the small intestine.

Distinct Developmental Requirements for Isolated Lymphoid Follicle Formation in the Small and Large Intestine

“…7,[12][13][14] We have previously shown that RANKL is expressed on stromal cells found throughout CPs, but is preferentially expressed by stromal cells located in the subepithelial dome of ILFs and PPs. 15 We also showed RANKL appears on stromal cells later in ontogeny than other stromal cell antigens including the follicular dendritic cell marker FDC-M1, vascular cell adhesion molecule 1 (VCAM-1), and CD157, and can still be induced when LT␣ 1 ␤ 2 signaling through the LT␤R is blocked. In this study, we used RANKL Ϫ/Ϫ mice to further investigate the role of RANKL in the development of CPs and ILFs, and found that in the absence of RANKL small intestinal, but not colonic, CPs fail to express CXCL13, recruit B cells, or develop into ILFs.…”

“…15 In previous studies, we showed that aly/aly mice lacking functional NF-B-inducing kinase (NIK) or wild-type mice in which LT␣ 1 ␤ 2 signaling was blocked with LT␤R-Ig also had defective stromal antigen expression in CPs, failing to express VCAM-1, CD157, and FDC-M1, but retaining RANKL expression. The CPs from the aly/aly mice also failed to develop into ILFs.…”

“…15 Although all CPs in the RANKL Ϫ/Ϫ small intes- tine included FDC-M1 ϩ stromal cells, most of these CPs did not include any stromal cells expressing VCAM-1 or CD157 ( Figure 7A). None of the small intestinal CPs from RANKL Ϫ/Ϫ mice examined had both VCAM-1 ϩ and CD157 ϩ stromal cells, the pattern found in all control CPs.…”

“…with purified human LT␤R-Ig fusion protein as described previously. 15 Injections of 100 g of LT␤R-Ig were given on embryonic days 14 and 16. The RANKL ϩ/Ϫ and RANKL Ϫ/Ϫ offspring were sacrificed at 8 weeks of age, and tissue from the small intestine was analyzed.…”

“…ILF development in wild-type mice can be enhanced by in utero treatment with LT␤R-Ig, which blocks formation of PPs leading to a compensatory increase in the number of ILFs. 15,19 Pregnant RANKL ϩ/Ϫ female mice that had been bred with RANKL Ϫ/Ϫ male mice were treated with LT␤R-Ig. The resultant RANKL Ϫ/Ϫ and control RANKL ϩ/Ϫ offspring lacked PPs, indicating the treatment successfully blocked PP development.…”