G-Protein Coupled Receptor 18 Contributes to Establishment of the CD8 Effector T Cell Compartment.

The requirements for effector and memory CD8 T cell development are incompletely understood. Recent work has revealed a role for G-protein coupled receptor 18 (GPR18) in establishment of the intestinal CD8αα intraepithelial lymphocyte compartment. Here, we report that GPR18 is also functionally expressed in conventional CD8αβ T cells. When the receptor is lacking, mice develop fewer CD8+ KLRG1+ Granzyme B+ effector-memory cells. Bone marrow chimera studies show that the GPR18 requirement is CD8 T cell intrinsic. GPR18 is not required for T-bet expression in KLRG1+ CD8 T cells. Gene transduction experiments confirm the functional activity of GPR18 in CD8 T cells. In summary, we describe a novel GPCR requirement for establishment or maintenance of the CD8 KLRG1+ effector-memory T cell compartment. These findings have implications for methods to augment CD8 effector cell numbers

The G protein-coupled receptor P2RY8 and follicular dendritic cells promote germinal center confinement of B cells, whereas S1PR3 can contribute to their dissemination.

The orphan Gα13-coupled receptor P2RY8 is mutated in human germinal center (GC)-derived lymphomas and was recently found to promote B cell association with GCs in a mouse model. Here we establish that P2RY8 promotes clustering of activated B cells within follicles in a follicular dendritic cell (FDC)-dependent manner. Although mice lack a P2RY8 orthologue, we show that mouse GC B cell clustering is also dependent on FDCs acting to support the function of a Gα13-coupled receptor. Mutations in GNA13 and its downstream effector ARHGEF1 are associated with the development of disseminated GC-derived lymphomas. We find that egress of Gna13 mutant GC B cells from lymph nodes in the mouse depends on sphingosine-1-phosphate receptor-3. These findings provide evidence that FDCs promote GC confinement of both human and mouse GC B cells via Gα13-dependent pathways, and they show that dissemination of Gα13-deficient GC B cells additionally requires an egress-promoting receptor

Protein tyrosine phosphatase 1C negatively regulates antigen receptor signaling in B lymphocytes and determines thresholds for negative selection

AbstractMotheaten viable (mev) mice are deficient in the cytosolic protein tyrosine phosphatase, PTP1C, and exhibit severe B cell immunodeficiency and autoantibody production. The role of PTP1 C in B cell selection and function was analyzed by breeding immunoglobulin transgenes specific for a defined antigen, hen egg lysozyme, into mav mice. Antigen triggered a greater and more rapid elevation of intracellular calcium in PTP1 C-deficient B cells, indicating that this phosphatase negatively regulates immunoglobulin signaling. Elimination of self-reactive B cells carrying this signal-enhancing mutation was triggered during their development by binding a lower valency form of self-antigen than is normally required. These findings establish that activation of distinct repertoire-censoring mechanisms depends on quantitative differences in antigen receptor signaling, whose thresholds are determined by negative regulation through PTP1C

Thymic egress: S1P of 1000

Recent studies have begun to illuminate the mechanism of T-cell export from the thymus, with the identification of a required lysophospholipid receptor, two upstream transcription factors, and several downstream regulators of cytoskeleton dynamics. This work has generated immediate translational impact, aiding the design of immunosuppressant drugs and the identification of a novel form of human immunodeficiency

S-Geranylgeranyl-L-glutathione is a ligand for human B cell-confinement receptor P2RY8.

Germinal centres are important sites for antibody diversification and affinity maturation, and are also a common origin of B cell malignancies. Despite being made up of motile cells, germinal centres are tightly confined within B cell follicles. The cues that promote this confinement are incompletely understood. P2RY8 is a Gα13-coupled receptor that mediates the inhibition of migration and regulates the growth of B cells in lymphoid tissues1,2. P2RY8 is frequently mutated in germinal-centre B cell-like diffuse large B cell lymphoma (GCB-DLBCL) and Burkitt lymphoma1,3-6, and the ligand for this receptor has not yet been identified. Here we perform a search for P2RY8 ligands and find P2RY8 bioactivity in bile and in culture supernatants of several mouse and human cell lines. Using a seven-step biochemical fractionation procedure and a drop-out mass spectrometry approach, we show that a previously undescribed biomolecule, S-geranylgeranyl-L-glutathione (GGG), is a potent P2RY8 ligand that is detectable in lymphoid tissues at the nanomolar level. GGG inhibited the chemokine-mediated migration of human germinal-centre B cells and T follicular helper cells, and antagonized the induction of phosphorylated AKT in germinal-centre B cells. We also found that the enzyme gamma-glutamyltransferase-5 (GGT5), which was highly expressed by follicular dendritic cells, metabolized GGG to a form that did not activate the receptor. Overexpression of GGT5 disrupted the ability of P2RY8 to promote B cell confinement to germinal centres, which indicates that GGT5 establishes a GGG gradient in lymphoid tissues. This work defines GGG as an intercellular signalling molecule that is involved in organizing and controlling germinal-centre responses. As the P2RY8 locus is modified in several other types of cancer in addition to GCB-DLBCL and Burkitt lymphoma, we speculate that GGG might have organizing and growth-regulatory roles in multiple human tissues

Integrin-dependence of Lymphocyte Entry into the Splenic White Pulp

The steps involved in lymphocyte homing to the white pulp cords of the spleen are poorly understood. We demonstrate here that the integrins lymphocyte function associated (LFA)-1 and α4β1 make essential and mostly overlapping contributions necessary for B cell migration into white pulp cords. T cell entry to the white pulp is also reduced by blockade of LFA-1 and α4β1. The LFA-1 ligand, intercellular adhesion molecule 1 is critical for lymphocyte entry and both hematopoietic cells and radiation-resistant cells contribute to this requirement. Vascular cell adhesion molecule 1 contributes to the α4β1 ligand requirement and a second ligand, possibly fibronectin, also plays a role. By contrast with the entry requirements, antigen-induced movement of B cells from follicles to the outer T zone is not prevented by integrin blocking antibodies. Comparison of the distribution of integrin-blocked B cells and B cells treated with the Gαi inhibitor, pertussis toxin, early after transfer reveals in both cases reduced accumulation in the inner marginal zone. These observations suggest that chemokine receptor signaling and the integrins LFA-1 and α4β1 function together to promote lymphocyte transit from the marginal zone into white pulp cords

Sphingosine-1-phosphate receptor 2 restrains egress of γδ T cells from the skin.

Maintenance of a population of IL-17-committed γδ T cells in the dermis is important in promoting tissue immunity. However, the signals facilitating γδ T cell retention within the dermis remain poorly understood. Here, we find that sphingosine-1-phosphate receptor 2 (S1PR2) acts in a cell-intrinsic manner to oppose γδ T cell migration from the dermis to the skin draining lymph node (dLN). Migration of dermal γδ T cells to the dLN under steady-state conditions occurs in an S1PR1-dependent manner. S1PR1 and CD69 are reciprocally expressed on dermal γδ T cells, with loss of CD69 associated with increased S1PR1 expression and enhanced migration to the dLN. γδ T cells lacking both S1PR2 and CD69 are impaired in their maintenance within the dermis. These findings provide a mechanism for how IL-17+ γδ T cells establish residence within the dermis and identify a role for S1PR2 in restraining the egress of tissue-resident lymphocytes

Immune complex relay by subcapsular sinus macrophages and noncognate B cells drives antibody affinity maturation.

Subcapsular sinus (SCS) macrophages capture antigens from lymph and present them intact for B cell encounter and follicular delivery. However, the properties of SCS macrophages are poorly defined. Here we show SCS macrophage development depended on lymphotoxin-alpha1beta2, and the cells had low lysosomal enzyme expression and retained opsonized antigens on their surface. Intravital imaging revealed immune complexes moving along macrophage processes into the follicle. Moreover, noncognate B cells relayed antigen opsonized by newly produced antibodies from the subcapsular region to the germinal center, and affinity maturation was impaired when this transport process was disrupted. Thus, we characterize SCS macrophages as specialized antigen-presenting cells functioning at the apex of an antigen transport chain that promotes humoral immunity

Overlapping Roles of CXCL13, Interleukin 7 Receptor α, and CCR7 Ligands in Lymph Node Development

Lymphoid tissue development is associated with local accumulation of CD4+ CD3− IL-7Rαhi hematopoietic cells that deliver lymphotoxin (LT)α1β2 signals to resident stromal cells. Previous studies have established an important role for CXCL13 (BLC) in the development of Peyer's patches (PP) and some peripheral lymph nodes (LNs), but the chemokine requirements for several LN types, including mesenteric LNs, remain undefined. Using CXCL13−/− mice that additionally carry the paucity of LN T cell mutation (plt/plt), we discovered that CCR7 ligands function in peripheral LN development. We also tested for a genetic interaction during LN development between CXCL13 and a cytokine receptor required in PP development, IL-7Rα. Mice deficient for both CXCL13 and IL-7Rα displayed a striking absence of LNs, including mesenteric LNs. These data extend the role of CXCL13 to the development of all LNs and establish a previously unappreciated role for IL-7Rα in this process. Both circulating and LN CD4+ CD3− IL-7Rαhi cells are shown to express LTα1β2 in an IL-7Rα–dependent manner. Furthermore, CXCL13 was found to be sufficient to mediate CD4+ CD3− IL-7Rαhi cell recruitment in vivo to an ectopic site. These findings indicate that CXCL13 and CCR7 ligands promote accumulation of CD4+ CD3− IL-7Rαhi cells, delivering IL-7Rα–dependent LTα1β2 signals critical for LN development