An ENU-induced mutation in the lymphotoxin alpha gene impairs organogenesis of lymphoid tissues in C57BL/6 mice

Lymphotoxin: from the physiology to the regeneration of the thymic function

The members of the Tumor Necrosis Factor (TNF) superfamily, the ligand lymphotoxin α1β2 (LTα1β2) and its unique receptor lymphotoxin β receptor (LTβR), play a pivotal role in the establishment and regulation of the immune system by allowing a tight communication between lymphocytes and stromal cells. Recent advances using transgenic mice harboring a specific deletion of the Ltbr gene in distinct stromal cells have revealed important roles for LTβR signaling in the thymic function that ensures the generation of a diverse and self-tolerant T-cell repertoire. In this review, we summarize our current knowledge on this signaling axis in the thymic homing of lymphoid progenitors and peripheral antigen-presenting cells, the trafficking and egress of thymocytes, the differentiation of medullary thymic epithelial cells, and the establishment of central tolerance. We also highlight the importance of LTα1β2/LTβR axis in controlling the recovery of the thymic function after myeloablative conditioning regimen, opening novel perspectives in regenerative medicine.

B cells regulate antibody responses through the medullary remodeling of inflamed lymph nodes

Lymph node (LN) structure is remodeled during immune responses, a process which is considered to play an important role in the regulation of immune function. To date, little attention has been paid to the remodeling of the medullary region, despite its proposed role as a niche for antibody-producing plasma cells. Here, we show that B cells mediate medullary remodeling of antigen-draining LNs during inflammation. This process occurs with kinetics similar to changes in plasma cell number and is accompanied by stromal renetworking which manifests as the segregation of B cells and plasma cells. Medullary remodeling depends on signaling via the lymphotoxin-β receptor and the presence of B cells but occurs independently of T-dependent humoral responses or other immune cell subsets including T cells, monocytes and neutrophils. Moreover, reconstitution of non-cognate polyclonal B cells in B cell-deficient mice restores not only the medullary remodeling but also the antibody response by separately transferred cognate B cells, suggesting that non-cognate B cells contribute to antibody responses through medullary remodeling. We propose that non-cognate B cells mediate the expansion of the plasma cell niche in LN through medullary remodeling, thereby regulating the size of the LN plasma cell pool.

The Sweet Pee model for Sglt2 mutation

Inhibiting renal glucose transport is a potential pharmacologic approach to treat diabetes. The renal tubular sodium-glucose transporter 2 (SGLT2) reabsorbs approximately 90% of the filtered glucose load. An animal model with sglt2 dysfunction could provide information regarding the potential long-term safety and efficacy of SGLT2 inhibitors, which are currently under clinical investigation. Here, we describe Sweet Pee, a mouse model that carries a nonsense mutation in the Slc5a2 gene, which results in the loss of sglt2 protein function. The phenotype of Sweet Pee mutants was remarkably similar to patients with mutations in the Scl5a2 gene. The Sweet Pee mutants had improved glucose tolerance, higher urinary excretion of calcium and magnesium, and growth retardation. Renal physiologic studies demonstrated a prominent distal osmotic diuresis without enhanced natriuresis. Sweet Pee mutants did not exhibit increased KIM-1 or NGAL, markers of acute tubular injury. After induction of diabetes, Sweet Pee mice had better overall glycemic control than wild-type control mice, but had a higher risk for infection and an increased mortality rate (70% in homozygous mutants versus 10% in controls at 20 weeks). In summary, the Sweet Pee model allows study of the long-term benefits and risks associated with inhibition of SGLT2 for the management of diabetes. Our model suggests that inhibiting SGLT2 may improve glucose control but may confer increased risks for infection, malnutrition, volume contraction, and mortality.