The costimulatory molecule CD226 signals through VAV1 to amplify TCR signals and promote IL-17 production by CD4+ T cells

The activation of T cells requires the guanine nucleotide exchange factor VAV1. Using mice in which a tag for affinity purification was attached to endogenous VAV1 molecules, we analyzed by quantitative mass spectrometry the signaling complex that assembles around activated VAV1. Fifty VAV1-binding partners were identified, most of which had not been previously reported to participate in VAV1 signaling. Among these was CD226, a costimulatory molecule of immune cells. Engagement of CD226 induced the tyrosine phosphorylation of VAV1 and synergized with T cell receptor (TCR) signals to specifically enhance the production of interleukin-17 (IL-17) by primary human CD4⁺ T cells. Moreover, co-engagement of the TCR and a risk variant of CD226 that is associated with autoimmunity (rs763361) further enhanced VAV1 activation and IL-17 production. Thus, our study reveals that a VAV1-based, synergistic cross-talk exists between the TCR and CD226 during both physiological and pathological T cell responses and provides a rational basis for targeting CD226 for the management of autoimmune diseases.

Themis1 enhances T cell receptor signaling during thymocyte development by promoting Vav1 activity and Grb2 stability

The T cell signaling protein Themis1 is essential for the positive and negative selection of thymocytes in the thymus. Although the developmental defect that results from the loss of Themis1 suggests that it enhances T cell receptor (TCR) signaling, Themis1 also recruits Src homology 2 domain-containing phosphatase-1 (SHP-1) to the vicinity of TCR signaling complexes, suggesting that it has an inhibitory role in TCR signaling. We used TCR signaling reporter mice and quantitative proteomics to explore the role of Themis1 in developing T cells. We found that Themis1 acted mostly as a positive regulator of TCR signaling in vivo when receptors were activated by positively selecting ligands. Proteomic analysis of the Themis1 interactome identified SHP-1, the TCR-associated adaptor protein Grb2, and the guanine nucleotide exchange factor Vav1 as the principal interacting partners of Themis1 in isolated mouse thymocytes. Analysis of TCR signaling in Themis1-deficient and Themis1-overexpressing mouse thymocytes demonstrated that Themis1 promoted Vav1 activity both in vitro and in vivo. The reduced activity of Vav1 and the impaired T cell development in Themis1(-/-) mice were due in part to increased degradation of Grb2, which suggests that Themis1 is required to maintain the steady-state abundance of Grb2 in thymocytes. Together, these data suggest that Themis1 acts as a positive regulator of TCR signaling in developing T cells, and identify a mechanism by which Themis1 regulates thymic selection.

Cell growth in aggregates determines gene expression, proliferation, survival, chemoresistance, and sensitivity to immune effectors in follicular lymphoma

Lymphomas grow as dense aggregates in patients, but whether this spatial organization affects lymphoma cell biology is unknown. We grew follicular lymphoma (FL) cells in vitro as multicellular aggregates of lymphoma cells to investigate this question. Gene expression analysis revealed that 612 genes were differentially expressed when cells grew in multicellular aggregates of lymphoma cells rather than in suspension. These genes correspond to several GO biological processes, such as hypoxia, activation of NF-κB pathway, and negative regulation of cell cycle, a gene signature also found in the transcriptomes from FL biopsies. Pimonidazole staining, HIF-1A accumulation, and VEGFA release confirmed that cells in multicellular aggregates of lymphoma cells actually respond to hypoxia. In adaptation to such conditions, they also displayed an activated NF-κB pathway and a quiescent status far more frequently than in suspension. When cultured in three dimensions, FL cells display resistance to doxorubicin and bendamustine, two drugs largely used in FL therapy, compared to FL cultured in suspension. Finally, multicellular aggregates of lymphoma cells were also found to be less sensitive to purified natural killer cells. To conclude, our study shows that in FL, spatial organization results in dramatic changes in FL biology, including gene expression, proliferation, drug resistance, and immune escape.

The gene expression profile of phosphoantigen-specific human γδ T lymphocytes is a blend of αβ T-cell and NK-cell signatures

Global transcriptional technologies have revolutionised the study of lymphoid cell populations, but human γδ T lymphocytes specific for phosphoantigens remain far less deeply characterised by these methods despite the great therapeutic potential of these cells. Here we analyse the transcriptome of circulating TCRVγ(+) γδ T cells isolated from healthy individuals, and their relation with those from other lymphoid cell subsets. We report that the gene signature of phosphoantigen-specific TCRVγ(+) γδ T cells is a hybrid of those from αβ T and NK cells, with more 'NK-cell' genes than αβ T cells have and more 'T-cell' genes than NK cells. The expression profile of TCRVγ(+) γδ T cells stimulated with phosphoantigen recapitulates their immediate physiological functions: Th1 cytokine, chemokine and cytotoxic activities reflect their high mitotic activity at later time points and do not indicate antigen-presenting functions. Finally, such hallmarks make the transcriptome of γδ T cells, whether resting or clonally expanding, clearly distinctive from that of NK/T or peripheral T-cell lymphomas of the γδ subtype.

PAX5 mutations occur frequently in adult B-cell progenitor acute lymphoblastic leukemia and PAX5 haploinsufficiency is associated with BCR-ABL1 and TCF3-PBX1 fusion genes: a GRAALL study

Adult and child B-cell progenitor acute lymphoblastic leukemia (BCP-ALL) differ in terms of incidence and prognosis. These disparities are mainly due to the molecular abnormalities associated with these two clinical entities. A genome-wide analysis using oligo SNP arrays recently demonstrated that PAX5 (paired-box domain 5) is the main target of somatic mutations in childhood BCP-ALL being altered in 38.9% of the cases. We report here the most extensive analysis of alterations of PAX5 coding sequence in 117 adult BCP-ALL patients in the unique clinical protocol GRAALL-2003/GRAAPH-2003. Our study demonstrates that PAX5 is mutated in 34% of adult BCP-ALL, mutations being partial or complete deletion, partial or complete amplification, point mutation or fusion gene. PAX5 alterations are heterogeneous consisting in complete loss in 17%, focal deletions in 10%, point mutations in 7% and translocations in 1% of the cases. PAX5 complete loss and PAX5 point mutations differ. PAX5 complete loss seems to be a secondary event and is significantly associated with BCR-ABL1 or TCF3-PBX1 fusion genes and a lower white blood cell count.

Decreased motivational properties of morphine in mouse models of cancerous- or inflammatory-chronic pain: implication of supraspinal neuropeptide FF(2) receptors

Our main purpose was to evaluate the influence of cancer pain on the rewarding properties of morphine. Opioids are very addictive when used by healthy persons, conversely the occurrence of an opioid addiction seems very low when patients suffering from cancer are treated with morphine. We investigated the reinforcing properties of morphine in the place preference paradigm on a new model of mice suffering from a cancer pain induced by syngenic melanoma cells injected in the hind paw. These data were compared with mice suffering either from a short-term- or a chronic-inflammatory pain induced respectively by injection of carrageenan or complete Freund's adjuvant. Remarkably, mice suffering from cancer pain or chronic inflammatory pain did not develop any preference for the environment associated with the injection of morphine. In mice injected with melanoma cells, the specific binding of [(125)I]EYWSLAAPQRF-NH(2), an agonist of neuropeptide FF(2) receptors, was increased in several brain areas involved in the rewarding properties of opiates, including the shell of the nucleus accumbens, the major islands of Calleja, the ventral endopiriform nucleus and the amygdaloid area. Our study is the first to reveal a modification of morphine rewarding properties under cancer pain in rodents. We postulate that anti-opioid neuropeptides might contribute to the suppression of morphine rewarding effects in this murine model of cancer pain.

In situ immunologic characterization of follicular lymphomas

Surface markers were studied in a series of follicular lymphomas with immunofluorescence on frozen sections (39 cases) and on cell suspensions (21 cases), and with immunoperoxidase on frozen sections using a panel of 15 monoclonal antibodies (17 cases). With immunofluorescence on frozen sections, 22/39 cases showed monotypic sIg (IgMK: 14 cases, IgML: 7 cases, M: 1 case). In the remaining 17 cases the neoplastic follicles were negative. Nevertheless, even if sIg is not detected, the absence of an extracellular immunoglobulin network is indicative of the neoplastic, and not of the reactive nature of lymphoid follicles. The results obtained with immunofluorescence on frozen sections and on cell suspensions were identical in about half of the cases. In 9/21 cases monotypic sIg were detected by only one of these two methods. All the 17 cases studied with immunoperoxidase on frozen sections using monoclonal antibodies demonstrated monotypic sIg. On low magnification 6/17 sIg+ exhibited a nodular staining pattern while 7/17 cases this staining was diffuse. In 4/17 cases the staining pattern for heavy and light chains was different. A thin mantle zone, with sIgM plus sIgD cells, was observed in only 4 cases. Anti-HLA-DR and Leu-10 were positive in all cases. T cells positive for OKT3 were mainly distributed in the interfollicular areas; OKT4+ cells outnumbered OKT8+ cells. Within the neoplastic follicles, T cells stained mainly for OKT4 and OKT8+ cells were scarce. Leu-7+ cells predominated within the neoplastic nodules in 5 cases. With the anti-dendritic reticulum cell monoclonal antibody, all 17 cases showed a network, usually more loosely arranged than in reactive follicles. In 4 cases, of follicular and diffuse lymphoma, this network was extremely dissociated and in some areas these cells were scanty or lacking. We concluded that immunoperoxidase on frozen sections, using monoclonal antibodies, appears to be the most reliable method for the immunological phenotyping of follicular lymphomas.

[Chronic diarrhea in nonspecific colopathies in children. Trial of etiological classification]

305 children with non specific colopathies were studied with respect to the etiologic factors which may be responsible for the onset of the diarrheic syndrome. Epidemiologic factors (ethnic group, mode of housing, standard of living, parents's age and profession) did not appear to play a significant role and studies of familial and personal histories did not appear to be of any help. On the contrary, analysis of the diet showed a high incidence of nutritional imbalances (75.2% of cases) especially with respect to hyperprotidic diets. The role of a major and repeated antibiotic therapy and of psychologic problems may be suggested in 46 (15%) and 36 (11.8%) of the 305 cases, respectively. Fiberoptic and histologic investigations of the proctosigmoid mucosa were performed in 67 children: an inflammatory aspect was found in 22. In 21 of these 22 cases, no etiologic factors could be found and these cases, especially those occurring before 6 months of age, might belong to a special clinical entity.

Richter's syndrome. Evidence for the clonal origin of the two proliferations

A case of Richter's syndrome was investigated by several technics: light and electron microscopy, surface markers, immunohistological studies and immunoelectron microscopy. On light microscopy lymph node proliferation was composed of large lymphoid cells, some exhibiting Reed-Sternberg like features. On electron microscopy many intermediary cells, from small lymphocytes to immunoblasts and plasma cells, were noted. The circulating small lymphocytes were characterized as B cells (SIg +; MRBC+). The lymph node cells shared the same SIg phenotype (IgMK) but the percentage of MRBC was slightly lower. Immunohistological studies showed that lymph node cells were stained exclusively by anti micron and anti kappa antisera. These results are indicative of the B clonal origin of the two cell proliferations. Immunoelectron microscopy showed three staining patterns: 1) cells presenting only surface staining, 2) cells with diffuse staining presumably related to ribosomal fixation, 3) cells with endoplasmic reticulum staining. The significance of these three patterns is discussed with regard to B lymphocyte differentiation.

Granulomatous hepatitis in Q fever

Liver lesions in 17 patients with serologically diagnosed Q fever are described. A distinctive granulomatous pattern, with granuloma formation plus a fibrinoid ring, was observed in 14 cases. In two cases the fibrinoid material consisted of fibrillar eosinophilic structures without an annular arrangement, interspersed among epithelioid cells. In only one case was a nonspecific granuloma (devoid of fibrinoid material) noted. We conclude that the association of a granuloma with fibrinoid material is highly indicative of Q fever, but serial sections are often necessary to demonstrate this pattern.