A novel two-score system for interferon status segregates autoimmune diseases and correlates with clinical features

Measurement of type I interferon (IFN-I) has potential to diagnose and stratify autoimmune diseases, but existing results have been inconsistent. Interferon-stimulated-gene (ISG) based methods may be affected by the modularity of the ISG transcriptome, cell-specific expression, response to IFN-subtypes and bimodality of expression. We developed and clinically validated a 2-score system (IFN-Score-A and -B) using Factor Analysis of 31 ISGs measured by TaqMan selected from 3-IFN-annotated modules. We evaluated these scores using in-vitro IFN stimulation as well as in sorted cells then clinically validated in a cohort of 328 autoimmune disease patients and healthy controls. ISGs varied in response to IFN-subtypes and both scores varied between cell subsets. IFN-Score-A differentiated Systemic Lupus Erythematosus (SLE) from both Rheumatoid Arthritis (RA) and Healthy Controls (HC) (both p < 0.001), while IFN-Score-B differentiated SLE and RA from HC (both p < 0.001). In SLE, both scores were associated with cutaneous and hematological (all p < 0.05) but not musculoskeletal disease activity. Comparing with bimodal (IFN-high/low) classification, significant differences in IFN-scores were found between diagnostic groups within the IFN-high group. Our continuous 2-score system is more clinically relevant than a simple bimodal classification of IFN status. This system should allow improvement in diagnosis, stratification, and therapy in IFN-mediated autoimmunity.

S1PR1 drives a feedforward signalling loop to regulate BATF3 and the transcriptional programme of Hodgkin lymphoma cells

The Hodgkin/Reed-Sternberg cells of classical Hodgkin lymphoma (HL) are characterised by the aberrant activation of multiple signalling pathways. Here we show that a subset of HL displays altered expression of sphingosine-1-phosphate (S1P) receptors (S1PR)s. S1P activates phosphatidylinositide 3-kinase (PI3-K) in these cells that is mediated by the increased expression of S1PR1 and the decreased expression of S1PR2. We also showed that genes regulated by the PI3-K signalling pathway in HL cell lines significantly overlap with the transcriptional programme of primary HRS cells. Genes upregulated by the PI3-K pathway included the basic leucine zipper transcription factor, ATF-like 3 (BATF3), which is normally associated with the development of dendritic cells. Immunohistochemistry confirmed that BATF3 was expressed in HRS cells of most HL cases. In contrast, in normal lymphoid tissues, BATF3 expression was confined to a small fraction of CD30-positive immunoblasts. Knockdown of BATF3 in HL cell lines revealed that BATF3 contributed to the transcriptional programme of primary HRS cells, including the upregulation of S1PR1. Our data suggest that disruption of this potentially oncogenic feedforward S1P signalling loop could provide novel therapeutic opportunities for patients with HL.

Signal transduction through Vav-2 participates in humoral immune responses and B cell maturation

B and T lymphocytes develop normally in mice lacking the guanine nucleotide exchange factor Vav-2. However, the immune responses to type II thymus-independent antigen as well as the primary response to thymus-dependent (TD) antigen are defective. Vav-2-deficient mice are also defective in their ability to switch immunoglobulin class, form germinal centers and generate secondary immune responses to TD antigens. Mice lacking both Vav-1 and Vav-2 contain reduced numbers of B lymphocytes and display a maturational block in the development of mature B cells. B cells from Vav-1(-/-)Vav-2(-/-) mice respond poorly to antigen receptor triggering, both in terms of proliferation and calcium release. These studies show the importance of Vav-2 in humoral immune responses and B cell maturation.

Large-cell lymphoma. An unusual late relapse

We report a case of a 40-year-old man with a stage 4, anaplastic, large-cell lymphoma. He had been diagnosed 13 years before as having a liposarcoma, at which point he was treated with combination chemotherapy, which included anthracycline. On review of the histopathology from 13 years before, the original diagnosis of liposarcoma was revised to that of an anaplastic large-cell lymphoma. A diagnosis of relapsed anaplastic large-cell lymphoma was made. A MUGA scan showed a reduced ejection fraction of 46%. Our patient responded initially to combination chemotherapy, which included anthracycline, without further reduction in his ejection fraction. This was followed by high-dose chemotherapy and peripheral blood stem-cell transplantation. Twenty months later he is well and remains in complete remission.

Development of T-leukaemias in CD45 tyrosine phosphatase-deficient mutant lck mice

The CD45 tyrosine phosphatase lowers T-cell antigen receptor signalling thresholds by its positive actions on p56(lck) tyrosine kinase function. We now show that mice expressing active lck(F505) at non-oncogenic levels develop aggressive thymic lymphomas on a CD45(-/-) background. CD45 suppresses the tumorigenic potential of the kinase by dephosphorylation of the Tyr394 autophosphorylation site. In CD45(-/-) thymocytes the kinase is switched to a hyperactive oncogenic state, resulting in increased resistance to apoptosis. Transformation occurs in early CD4(-)CD8(-) thymocytes during the process of TCR-beta chain rearrangement by a recombinase-independent mechanism. Our findings represent the first example in which a tyrosine phosphatase in situ prevents the oncogenic actions of a SRC: family tyrosine kinase.

CD19 as a membrane-anchored adaptor protein of B lymphocytes: costimulation of lipid and protein kinases by recruitment of Vav

CD19 is a coreceptor that amplifies signaling by membrane immunoglobulin (mIg) to promote responses of the B lymphocyte to T-dependent antigens. Vav is a guanine nucleotide exchange factor for the Rho, Rac, Cdc42 family of small GTPases. We found that coligating mIg and CD19 causes a synergistic increase in the tyrosine phosphorylation of CD19. Phosphorylated tyrosine-391 of CD19 binds Vav to mediate a sustained increase in intracellular Ca2+ concentration. This response correlates with activation by the CD19-Vav complex of phosphatidylinositol 4-phosphate 5-kinase for the synthesis of phosphatidylinositol 4,5-bisphosphate. Interaction of CD19 with Vav also mediates the synergistic activation of the mitogen-activated protein kinase JNK. Therefore, CD19 is a membrane adaptor protein that recruits Vav for the activation of lipid and protein kinases.

Co-receptors of B lymphocytes

The past year has seen advances in our understanding of accessory membrane proteins that modulate the B cell response to antigen-receptor stimulation. The generation of complement receptor deficient mice has reinforced our appreciation of the importance of complement receptors in the B cell response to antigen. The association of inositol polyphosphate 5-phosphatase with FcgammaRIIB suggests another mechanism, in addition to recruitment of the phosphotyrosine phosphatase SHP-1, by which secreted immunoglobulin can limit further response to antigen. The in vivo function of CD22 in regulating the threshold of antigen-receptor signalling has been shown using CD22-deficient mice. Lastly, B cell receptor signalling in the B-1 subset of B lymphocytes has been demonstrated to be negatively regulated by CD5.