Staining of Ki67 and CTLA-4 in Tfr cells (left)

Staining of Ki67 and CTLA-4 in Tfr cells (left). B cell responses is usually highlighted by the lack of class switched antibodies in mice lacking Tfh cells (Crotty, 2011). Tfh cells are identified by expression of CXCR5, the chemokine receptor which guides them to GCs (Breitfeld et al., 2000; Crotty, 2011). Tfh cells also express high amounts of the transcription factor Bcl6 which is thought to control the Tfh cell program (Johnston et al., 2009) (Yu (+)-MK 801 Maleate et al., 2009) (Nurieva et al., 2009). Tfh cells are controlled by positive costimulatory signals through the inducible To cell costimulator (ICOS) and CD28 receptors, as well as co-inhibitory signals through Programmed death 1 (PD-1). ICOS encourages Tfh cell generation and maintenance, whereas PD-1 inhibits Tfh differentiation and/or leave into the blood (Akiba et al., 2005; Choi et al., 2011; Good-Jacobson et al., 2010; Hams et al., 2011; Kawamoto et al., 2012; Sage et al., 2013). T Follicular Regulatory (Tfr) cells are a newly defined, specialized effector subset of T regulatory (Treg) cells that suppress B cell responses (Chung et al., 2011; Linterman et al., 2011; Wollenberg et al., 2011). Like Tfh cells, Tfr cells express large levels of CXCR5, which guides them to GCs. The ability of Tfr cells to suppress B cell responses may be unique to Tfr cells because CXCR5Treg cells are unable to strongly suppress some GC B cell responses (Chung et al., 2011; Sage et al., 2013; Wollenberg et al., 2011). However , the precise role Tfr versus non-Tfr Treg cells in controlling W cell responses remains undetermined. Tfr cells are managed by positive and bad costimulatory signals; ICOS and CD28 promote Tfr cell development (Linterman et al., 2011; Sage et al., 2013), whereas PD-1 attenuates both Tfr cell generation and suppressive function (Sage et al., 2013). It has been proposed that within the GC, the family member proportions of Tfr to Tfh cells (as well as their functional capacity) regulates B cell responses, rather than absolute numbers of either cell type (Sage et al., 2013). Although CTLA-4 continues to be implicated in Rabbit polyclonal to CBL.Cbl an adapter protein that functions as a negative regulator of many signaling pathways that start from receptors at the cell surface. controlling W cell responses, the mechanism by which CTLA-4 regulates antibody production (+)-MK 801 Maleate remains unknown. CTLA-4 is a important mediator of Treg cell function and also controls standard T cells. CTLA-4 is usually constitutively expressed in Treg cell subsets, but induced upon activation in To (+)-MK 801 Maleate conventional cells (Walker, 2013). Germline deletion of CTLA-4 results in fatal multi-organ inflammation within 2 to 4 weeks of age (Tivol et al., 1995; Waterhouse et al., 1995), as well as increased antibody levels (Bour-Jordan et al., 2003; Walker et al., 2003). Treg-specific deletion of CTLA-4 recapitulates this great increase in antibody production, pointing to an essential role for CTLA-4 on Treg cells in limiting W cell responses (Wing et al., 2008). However , it is far from yet obvious whether CTLA-4 suppresses W cell responses by controlling Tfr, Treg and/or Tfh cells, due to the lethality associated with CTLA-4 global and Treg cell-specific deficiency, and the failure for blocking antibodies to target specific cells. There are data supporting cell intrinsic and cell extrinsic mechanisms through which CTLA-4 exerts its effects (Corse and Allison, 2012; Walker and Sansom, 2011; Walunas et al., 1996; Wang et al., 2012). CTLA-4 binds to B7-1 (+)-MK 801 Maleate (CD80) and B7-2 (CD86) with higher affinity than CD28. In vitro studies have demonstrated that CTLA-4 can attenuate B7-1 or B7-2 expression on dendritic cells either by downregulation or trans-endocytosis (Onishi et al., 2008; Qureshi et al., 2011; Wing et al., 2008). Whether CTLA-4 attenuates B7-1or B7-2 expression in vivo or if these CTLA-4 mediated cell-extrinsic mechanisms control W cell responses are still unclear. Here we investigate mobile mechanisms through which CTLA-4 regulates B cell responses using CTLA-4 inducible knockout strategies. We analyzed how CTLA-4 controls Tfh, Tfr, Treg and W cell responses. Our studies showed that CTLA-4 inhibited Tfh.