MICa/b-dependent activation of natural killer cells by CD64+ inflammatory type 2 dendritic cells contributes to autoimmunity.

Primary Sjögren's syndrome (pSS) is an inflammatory autoimmune disorder largely mediated by type I and II interferon (IFN). The potential contribution of innate immune cells, such as natural killer (NK) cells and dendritic cells (DC), to the pSS pathology remains understudied. Here, we identified an enriched CD16+ CD56hi NK cell subset associated with higher cytotoxic function, as well as elevated proportions of inflammatory CD64+ conventional dendritic cell (cDC2) subtype that expresses increased levels of MICa/b, the ligand for the activating receptor NKG2D, in pSS individuals. Circulating cDC2 from pSS patients efficiently induced activation of cytotoxic NK cells ex vivo and were found in proximity to CD56+ NK cells in salivary glands (SG) from pSS patients. Interestingly, transcriptional activation of IFN signatures associated with the RIG-I/DDX60 pathway, IFN I receptor, and its target genes regulate the expression of NKG2D ligands on cDC2 from pSS patients. Finally, increased proportions of CD64hi RAE-1+ cDC2 and NKG2D+ CD11b+ CD27+ NK cells were present in vivo in the SG after poly I:C injection. Our study provides novel insight into the contribution and interplay of NK and cDC2 in pSS pathology and identifies new potential therapy targets.

Tyrosine kinase 2 modulates splenic B cells through type I IFN and TLR7 signaling.

Tyrosine kinase 2 (TYK2) is involved in type I interferon (IFN-I) signaling through IFN receptor 1 (IFNAR1). This signaling pathway is crucial in the early antiviral response and remains incompletely understood on B cells. Therefore, to understand the role of TYK2 in B cells, we studied these cells under homeostatic conditions and following in vitro activation using Tyk2-deficient (Tyk2-/-) mice. Splenic B cell subpopulations were altered in Tyk2-/- compared to wild type (WT) mice. Marginal zone (MZ) cells were decreased and aged B cells (ABC) were increased, whereas follicular (FO) cells remained unchanged. Likewise, there was an imbalance in transitional B cells in juvenile Tyk2-/- mice. RNA sequencing analysis of adult MZ and FO cells isolated from Tyk2-/- and WT mice in homeostasis revealed altered expression of IFN-I and Toll-like receptor 7 (TLR7) signaling pathway genes. Flow cytometry assays corroborated a lower expression of TLR7 in MZ B cells from Tyk2-/- mice. Splenic B cell cultures showed reduced proliferation and differentiation responses after activation with TLR7 ligands in Tyk2-/- compared to WT mice, with a similar response to lipopolysaccharide (LPS) or anti-CD40 + IL-4. IgM, IgG, IL-10 and IL-6 secretion was also decreased in Tyk2-/- B cell cultures. This reduced response of the TLR7 pathway in Tyk2-/- mice was partially restored by IFNα addition. In conclusion, there is a crosstalk between TYK2 and TLR7 mediated by an IFN-I feedback loop, which contributes to the establishment of MZ B cells and to B cell proliferation and differentiation.

Mutations in TP53 and JAK2 are independent prognostic biomarkers in B-cell precursor acute lymphoblastic leukaemia.

BACKGROUND: In B-cell precursor acute lymphoblastic leukaemia (B-ALL), the identification of additional genetic alterations associated with poor prognosis is still of importance. We determined the frequency and prognostic impact of somatic mutations in children and adult cases with B-ALL treated with Spanish PETHEMA and SEHOP protocols. METHODS: Mutational status of hotspot regions of TP53, JAK2, PAX5, LEF1, CRLF2 and IL7R genes was determined by next-generation deep sequencing in 340 B-ALL patients (211 children and 129 adults). The associations between mutation status and clinicopathological features at the time of diagnosis, treatment outcome and survival were assessed. Univariate and multivariate survival analyses were performed to identify independent prognostic factors associated with overall survival (OS), event-free survival (EFS) and relapse rate (RR). RESULTS: A mutation rate of 12.4% was identified. The frequency of adult mutations was higher (20.2% vs 7.6%, P=0.001). TP53 was the most frequently mutated gene (4.1%), followed by JAK2 (3.8%), CRLF2 (2.9%), PAX5 (2.4%), LEF1 (0.6%) and IL7R (0.3%). All mutations were observed in B-ALL without ETV6-RUNX1 (P=0.047) or BCR-ABL1 fusions (P<0.0001). In children, TP53mut was associated with lower OS (5-year OS: 50% vs 86%, P=0.002) and EFS rates (5-year EFS: 50% vs 78.3%, P=0.009) and higher RR (5-year RR: 33.3% vs 18.6% P=0.037), and was independently associated with higher RR (hazard ratio (HR)=4.5; P=0.04). In adults, TP53mut was associated with a lower OS (5-year OS: 0% vs 43.3%, P=0.019) and a higher RR (5-year RR: 100% vs 61.4%, P=0.029), whereas JAK2mut was associated with a lower EFS (5-year EFS: 0% vs 30.6%, P=0.035) and a higher RR (5-year RR: 100% vs 60.4%, P=0.002). TP53mut was an independent risk factor for shorter OS (HR=2.3; P=0.035) and, together with JAK2mut, also were independent markers of poor prognosis for RR (TP53mut: HR=5.9; P=0.027 and JAK2mut: HR=5.6; P=0.036). CONCLUSIONS: TP53mut and JAK2mut are potential biomarkers associated with poor prognosis in B-ALL patients.

Immune-Regulatory Molecule CD69 Controls Peritoneal Fibrosis.

Patients with ESRD undergoing peritoneal dialysis develop progressive peritoneal fibrosis, which may lead to technique failure. Recent data point to Th17-mediated inflammation as a key contributor in peritoneal damage. The leukocyte antigen CD69 modulates the setting and progression of autoimmune and inflammatory diseases by controlling the balance between Th17 and regulatory T cells (Tregs). However, the relevance of CD69 in tissue fibrosis remains largely unknown. Thus, we explored the role of CD69 in fibroproliferative responses using a mouse model of peritoneal fibrosis induced by dialysis fluid exposure under either normal or uremic status. We found that cd69-/- mice compared with wild-type (WT) mice showed enhanced fibrosis, mesothelial to mesenchymal transition, IL-17 production, and Th17 cell infiltration in response to dialysis fluid treatment. Uremia contributed partially to peritoneal inflammatory and fibrotic responses. Additionally, antibody-mediated CD69 blockade in WT mice mimicked the fibrotic response of cd69-/- mice. Finally, IL-17 blockade in cd69-/- mice decreased peritoneal fibrosis to the WT levels, and mixed bone marrow from cd69-/- and Rag2-/-γc-/- mice transplanted into WT mice reproduced the severity of the response to dialysis fluid observed in cd69-/- mice, showing that CD69 exerts its regulatory function within the lymphocyte compartment. Overall, our results indicate that CD69 controls tissue fibrosis by regulating Th17-mediated inflammation.

BCR-JAK2 drives a myeloproliferative neoplasm in transplanted mice.

BCR-JAK2 is an infrequent gene fusion found in chronic/acute, myeloid/lymphoid Philadelphia chromosome-negative leukaemia. In this study, we demonstrated that in vivo expression of BCR-JAK2 in mice induces neoplasia, with fatal consequences. Transplantation of BCR-JAK2 bone marrow progenitors promoted splenomegaly, with megakaryocyte infiltration and elevated leukocytosis of myeloid origin. Analysis of peripheral blood revealed the presence of immature myeloid cells, platelet aggregates and ineffective erythropoiesis. A possible molecular mechanism for these observations involved inhibition of apoptosis by deregulated expression of the anti-apoptotic mediator Bcl-xL and the serine/threonine kinase Pim1. Together, these data provide a suitable in vivo molecular mechanism for leukaemia induction by BCR-JAK2 that validates the use of this model as a relevant preclinical tool for the design of new targeted therapies in Philadelphia chromosome-negative leukaemia involving BCR-JAK2-driven activation of the JAK2 pathway.

Genetic variants regulating the immune response improve the prediction of COVID-19 severity provided by clinical variables.

The characteristics of the host are crucial in the final outcome of COVID-19. Herein, the influence of genetic and clinical variants in COVID-19 severity was investigated in a total of 1350 patients. Twenty-one single nucleotide polymorphisms of genes involved in SARS-CoV-2 sensing as Toll-like-Receptor 7, antiviral immunity as the type I interferon signalling pathway (TYK2, STAT1, STAT4, OAS1, SOCS) and the vasoactive intestinal peptide and its receptors (VIP/VIPR1,2) were studied. To analyse the association between polymorphisms and severity, a model adjusted by age, sex and different comorbidities was generated by ordinal logistic regression. The genotypes rs8108236-AA (OR 0.12 [95% CI 0.02-0.53]; p = 0.007) and rs280519-AG (OR 0.74 [95% CI 0.56-0.99]; p = 0.03) in TYK2, and rs688136-CC (OR 0.7 [95% CI 0.5-0.99]; p = 0.046) in VIP, were associated with lower severity; in contrast, rs3853839-GG in TLR7 (OR 1.44 [95% CI 1.07-1.94]; p = 0.016), rs280500-AG (OR 1.33 [95% CI 0.97-1.82]; p = 0.078) in TYK2 and rs1131454-AA in OAS1 (OR 1.29 [95% CI 0.95-1.75]; p = 0.110) were associated with higher severity. Therefore, these variants could influence the risk of severe COVID-19.

Expression and function of dectin-1 is defective in monocytes from patients with systemic lupus erythematosus and rheumatoid arthritis.

The aim of this work was to study the expression and function of the innate immune receptor dectin-1 in patients with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). We studied twenty-six patients with SLE not receiving immunosuppressive therapy, twenty-six patients with RA, and fifteen controls. We found that monocytes from SLE patients showed a diminished expression of dectin-1 compared to healthy controls, and an inverse correlation between percent of dectin-1(+) cells and the disease activity score was detected. In addition, cells from SLE patients showed an abnormal calcium flux response induced by dectin-1 ligands as well as an enhanced release of IL-1ß, IL-6 and TNF-α, but not IL-23, upon dectin-1 engagement. Monocytes from patients with RA also showed a diminished expression, and a defective function of dectin-1. Our data suggest that dectin-1 receptor defects could contribute to the pathogenesis of autoimmune inflammatory conditions.

MAFB shapes human monocyte-derived macrophage response to SARS-CoV-2 and controls severe COVID-19 biomarker expression.

Monocyte-derived macrophages, the major source of pathogenic macrophages in COVID-19, are oppositely instructed by macrophage CSF (M-CSF) or granulocyte macrophage CSF (GM-CSF), which promote the generation of antiinflammatory/immunosuppressive MAFB+ (M-MØ) or proinflammatory macrophages (GM-MØ), respectively. The transcriptional profile of prevailing macrophage subsets in severe COVID-19 led us to hypothesize that MAFB shapes the transcriptome of pulmonary macrophages driving severe COVID-19 pathogenesis. We have now assessed the role of MAFB in the response of monocyte-derived macrophages to SARS-CoV-2 through genetic and pharmacological approaches, and we demonstrate that MAFB regulated the expression of the genes that define pulmonary pathogenic macrophages in severe COVID-19. Indeed, SARS-CoV-2 potentiated the expression of MAFB and MAFB-regulated genes in M-MØ and GM-MØ, where MAFB upregulated the expression of profibrotic and neutrophil-attracting factors. Thus, MAFB determines the transcriptome and functions of the monocyte-derived macrophage subsets that underlie pulmonary pathogenesis in severe COVID-19 and controls the expression of potentially useful biomarkers for COVID-19 severity.

Occurrence of SARS-CoV-2 viremia is associated with genetic variants of genes related to COVID-19 pathogenesis.

Introduction: SARS-CoV-2 viral load has been related to COVID-19 severity. The main aim of this study was to evaluate the relationship between SARS-CoV-2 viremia and SNPs in genes previously studied by our group as predictors of COVID-19 severity. Materials and methods: Retrospective observational study including 340 patients hospitalized for COVID-19 in the University Hospital La Princesa between March 2020 and December 2021, with at least one viremia determination. Positive viremia was considered when viral load was above the quantifiable threshold (20 copies/ml). A total of 38 SNPs were genotyped. To study their association with viremia a multivariate logistic regression was performed. Results: The mean age of the studied population was 64.5 years (SD 16.6), 60.9% patients were male and 79.4% white non-Hispanic. Only 126 patients (37.1%) had at least one positive viremia. After adjustment by confounders, the presence of the minor alleles of rs2071746 (HMOX1; T/T genotype OR 9.9 p < 0.0001), rs78958998 (probably associated with SERPING1 expression; A/T genotype OR 2.3, p = 0.04 and T/T genotype OR 12.9, p < 0.0001), and rs713400 (eQTL for TMPRSS2; C/T + T/T genotype OR 1.86, p = 0.10) were associated with higher risk of viremia, whereas the minor alleles of rs11052877 (CD69; A/G genotype OR 0.5, p = 0.04 and G/G genotype OR 0.3, p = 0.01), rs2660 (OAS1; A/G genotype OR 0.6, p = 0.08), rs896 (VIPR1; T/T genotype OR 0.4, p = 0.02) and rs33980500 (TRAF3IP2; C/T + T/T genotype OR 0.3, p = 0.01) were associated with lower risk of viremia. Conclusion: Genetic variants in HMOX1 (rs2071746), SERPING1 (rs78958998), TMPRSS2 (rs713400), CD69 (rs11052877), TRAF3IP2 (rs33980500), OAS1 (rs2660) and VIPR1 (rs896) could explain heterogeneity in SARS-CoV-2 viremia in our population.

Correction: Transmembrane protease serine 2 (TMPRSS2) rs75603675, comorbidity and sex are the primary predictors of Covid-19 severity.

We identified an error in the abstract of the article: TPMRSS2 rs75603675 OR is incorrectly indicated. It should read (OR = 2.140) instead of (OR = 0.586). We apologize for this error. However, since the main text is correct, it has no impact on the results displayed in the study.

Transmembrane protease serine 2 (TMPRSS2) rs75603675, comorbidity, and sex are the primary predictors of COVID-19 severity.

By the end of December 2021, coronavirus disease 2019 (COVID-19) produced more than 271 million cases and 5.3 million deaths. Although vaccination is an effective strategy for pandemic control, it is not yet equally available in all countries. Therefore, identification of prognostic biomarkers remains crucial to manage COVID-19 patients. The aim of this study was to evaluate predictors of COVID-19 severity previously proposed. Clinical and demographic characteristics and 120 single-nucleotide polymorphisms were analyzed from 817 patients with COVID-19, who attended the emergency department of the Hospital Universitario de La Princesa during March and April 2020. The main outcome was a modified version of the 7-point World Health Organization (WHO) COVID-19 severity scale (WHOCS); both in the moment of the first hospital examination (WHOCS-1) and of the severest WHOCS score (WHOCS-2). The TMPRSS2 rs75603675 genotype (OR = 0.586), dyslipidemia (OR = 2.289), sex (OR = 0.586), and the Charlson Comorbidity Index (OR = 1.126) were identified as the main predictors of disease severity. Consequently, these variables might influence COVID-19 severity and could be used as predictors of disease development.

SARS-CoV-2 Viremia Precedes an IL6 Response in Severe COVID-19 Patients: Results of a Longitudinal Prospective Cohort.

Background: Interleukin 6 (IL6) levels and SARS-CoV-2 viremia have been correlated with COVID-19 severity. The association over time between them has not been assessed in a prospective cohort. Our aim was to evaluate the relationship between SARS-CoV-2 viremia and time evolution of IL6 levels in a COVID-19 prospective cohort. Methods: Secondary analysis from a prospective cohort including COVID-19 hospitalized patients from Hospital Universitario La Princesa between November 2020 and January 2021. Serial plasma samples were collected from admission until discharge. Viral load was quantified by Real-Time Polymerase Chain Reaction and IL6 levels with an enzyme immunoassay. To represent the evolution over time of both variables we used the graphic command twoway of Stata. Results: A total of 57 patients were recruited, with median age of 63 years (IQR [53-81]), 61.4% male and 68.4% Caucasian. The peak of viremia appeared shortly after symptom onset in patients with persistent viremia (more than 1 sample with > 1.3 log10 copies/ml) and also in those with at least one IL6 > 30 pg/ml, followed by a progressive increase in IL6 around 10 days later. Persistent viremia in the first week of hospitalization was associated with higher levels of IL6. Both IL6 and SARS-CoV-2 viral load were higher in males, with a quicker increase with age. Conclusion: In those patients with worse outcomes, an early peak of SARS-CoV-2 viral load precedes an increase in IL6 levels. Monitoring SARS-CoV-2 viral load during the first week after symptom onset may be helpful to predict disease severity in COVID-19 patients.

Candida albicans beta-glucan exposure is controlled by the fungal CEK1-mediated mitogen-activated protein kinase pathway that modulates immune responses triggered through dectin-1.

Innate immunity to Candida albicans depends upon the recognition of molecular patterns on the fungal cell wall. However, the masking of major components such as beta-glucan seems to be a mechanism that fungi have evolved to avoid immune cell recognition through the dectin-1 receptor. Although the role of C. albicans mitogen-activated protein kinase (MAPK) pathways as virulence determinants has been established previously with animal models, the mechanism involved in this behavior is largely unknown. In this study we demonstrate that a disruption of the C. albicans extracellular signal-regulated kinase (ERK)-like 1 (CEK1)-mediated MAPK pathway causes enhanced cell wall beta-glucan exposure, triggering immune responses more efficiently than the wild type, as measured by dectin-1-mediated specific binding and human dendritic cell (hDC)- and macrophage-mediated phagocytosis, killing, and activation of intracellular signaling pathways. At the molecular level, the disruption of CEK1 resulted in altered spleen tyrosine kinase (Syk), Raf-1, and ERK1/2 activations together with IkappaB degradation on hDCs and increased dectin-1-dependent activator protein 1 (AP-1) activation on transfected cells. In addition, concurring with these altered pathways, we detected increased reactive oxygen species production and cytokine secretion. In conclusion, the CEK1-mediated MAPK pathway is involved in beta-glucan exposure in a fungal pathogen, hence influencing dectin-1-dependent immune cell recognition, thus establishing this fungal intracellular signaling route as a promising novel therapeutic target.

Candida albicans internalization by host cells is mediated by a clathrin-dependent mechanism.

Candida albicans is a major cause of oropharyngeal, vulvovaginal and haematogenously disseminated candidiasis. Endocytosis of C. albicans hyphae by host cells is a prerequisite for tissue invasion. This internalization involves interactions between the fungal invasin Als3 and host E- or N-cadherin. Als3 shares some structural similarity with InlA, a major invasion protein of the bacterium Listeria monocytogenes. InlA mediates entry of L. monocytogenes into host cells through binding to E-cadherin. A role in internalization, for a non-classical stimulation of the clathrin-dependent endocytosis machinery, was recently highlighted. Based on the similarities between the C. albicans and L. monocytogenes invasion proteins, we studied the role of clathrin in the internalization of C. albicans. Using live-cell imaging and indirect immunofluorescence of epithelial cells infected with C. albicans, we observed that host E-cadherin, clathrin, dynamin and cortactin accumulated at sites of C. albicans internalization. Similarly, in endothelial cells, host N-cadherin, clathrin and cortactin accumulated at sites of fungal endocytosis. Furthermore, clathrin, dynamin or cortactin depletion strongly inhibited C. albicans internalization by epithelial cells. Finally, beads coated with Als3 were internalized in a clathrin-dependent manner. These data indicate that C. albicans, like L. monocytogenes, hijacks the clathrin-dependent endocytic machinery to invade host cells.

Angioimmunoblastic T-cell lymphoma after acute myeloid leukemia: Alleged common pathogenesis. A case report and literature review.

The genomic landscape of AITL is characterized by mutation of epigenetic modifiers. This gene expression pattern resembles myeloid diseases and shows a potential role for hypomethylating agents as possible therapy for AITL.

TYK2 Variants in B-Acute Lymphoblastic Leukaemia.

B-cell precursor acute lymphoblastic leukaemia (B-ALL) is a malignancy of lymphoid progenitor cells with altered genes including the Janus kinase (JAK) gene family. Among them, tyrosine kinase 2 (TYK2) is involved in signal transduction of cytokines such as interferon (IFN) α/ß through IFN-α/ß receptor alpha chain (IFNAR1). To search for disease-associated TYK2 variants, bone marrow samples from 62 B-ALL patients at diagnosis were analysed by next-generation sequencing. TYK2 variants were found in 16 patients (25.8%): one patient had a novel mutation at the four-point-one, ezrin, radixin, moesin (FERM) domain (S431G) and two patients had the rare variants rs150601734 or rs55882956 (R425H or R832W). To functionally characterise them, they were generated by direct mutagenesis, cloned in expression vectors, and transfected in TYK2-deficient cells. Under high-IFNα doses, the three variants were competent to phosphorylate STAT1/2. While R425H and R832W induced STAT1/2-target genes measured by qPCR, S431G behaved as the kinase-dead form of the protein. None of these variants phosphorylated STAT3 in in vitro kinase assays. Molecular dynamics simulation showed that TYK2/IFNAR1 interaction is not affected by these variants. Finally, qPCR analysis revealed diminished expression of TYK2 in B-ALL patients at diagnosis compared to that in healthy donors, further stressing the tumour immune surveillance role of TYK2.

Regulated recruitment of DC-SIGN to cell-cell contact regions during zymosan-induced human dendritic cell aggregation.

Zymosan is a beta-glucan, mannan-rich yeast particle widely used to activate the inflammatory response of immune cells. We studied the zymosan-binding potential of human dendritic cells (hDCs) by using specific carbohydrate inhibitors and blocking monoclonal antibodies. We show that DC-specific intercellular adhesion molecule-grabbing nonintegrin (DC-SIGN) is a major nonopsonic recognition receptor for zymosan on hDCs. Indeed, blocking of DC-SIGN inhibited the inflammatory response of DCs to zymosan. We compared the zymosan-binding capacity of hDC-SIGN to that of Dectin-1 and complement receptor 3 (CR3), which are receptors involved in the nonopsonic recognition of these yeast-derived particles. Dectin-1- and DC-SIGN-K562 cells bound to zymosan particles, whereas CR3-K562 cells did not. DC-SIGN and Dectin-1 were also expressed in COS cells to compare their ability to trigger particle internalization in a nonphagocytic cell line. DC-SIGN transfectants were unable to internalize bound particles, indicating that DC-SIGN is primarily involved in recognition but not in particle internalization. Zymosan induced a rapid DC aggregation that was accompanied by a dramatic change of DC-SIGN distribution in the plasma membrane. Under resting conditions, DC-SIGN was diffusely distributed through the cell surface, displaying clusters at the free leading edge. Upon zymosan treatment, DC-SIGN was markedly redistributed to cell-cell contacts, supporting an adhesion role in DC-DC interactions. The mechanism(s) supporting DC-SIGN-mediated intercellular adhesion were further investigated by using DC-SIGN-K562 aggregation. DC-SIGN was highly concentrated at points of cell-cell contact, suggesting a role for enhanced avidity during DC-SIGN-mediated intercellular adhesion.

High molecular response rate and clinical correlation in patients with follicular lymphoma treated with cyclophosphamide-vincristine-prednisone plus interferon alpha 2b.

PURPOSE: The role of molecular monitoring of minimal residual disease (MRD) in low-grade non-Hodgkin's lymphoma is controversial. We have performed a prospective study of the molecular behavior of 35 patients with follicular non-Hodgkin's lymphoma who received cyclophosphamide-vincristine-prednisone chemotherapy in conjunction with IFN-alpha 2b. EXPERIMENTAL DESIGN: Bcl-2 and clonal immunoglobulin heavy chain (IgH) gene rearrangements were assayed at diagnosis by PCR in lymph node and bone marrow (BM) and sequentially after treatment. RESULTS: Molecular markers were detected in BM of 29 (83%) patients at diagnosis: Bcl-2 rearrangement in 20 patients (90% major breakpoint and 10% minor cluster) and clonal IgH rearrangement in 9 of 15 patients negative for Bcl-2. Molecular and clinical response was noted in 25 (86%) patients after induction treatment. Progression-free survival at 5 years was 78.1 +/- 8%. A correlation between clinical and molecular response was found in 24 patients with molecular markers in BM at diagnosis and >2 years of follow-up: 94% of patients with undetectable MRD showed continuous clinical remission, whereas 50% of patients who reverted back to positive molecular markers relapsed (P < 0.05). CONCLUSIONS: The rate of molecular response is high in patients treated with cyclophosphamide-vincristine-prednisone and IFN and MRD sequential analysis is useful for disease surveillance.

Chemokine receptors that mediate B cell homing to secondary lymphoid tissues are highly expressed in B cell chronic lymphocytic leukemia and non-Hodgkin lymphomas with widespread nodular dissemination.

B cell neoplasms present heterogeneous patterns of lymphoid organ involvement, which may be a result of the differential expression of chemokine receptors. We found that chemokine receptor (CCR)7, CXC chemokine receptor (CXCR)4, or CXCR5, the main chemokine receptors that mediate B cell entry into secondary lymphoid tissues and their homing to T cell and B cell zones therein, were highly expressed in B malignancies with widespread involvement of lymph nodes. Conversely, those pathologies with little or no nodular dissemination showed no expression to very low levels of CCR7 and CXCR5 and low to moderate levels of CXCR4. These findings provide evidence for the role of CCR7, CXCR4, and CXCR5 in determining the pattern of lymphoid organ involvement of B tumors. Functional studies were performed on B malignancies expressing different levels of CCR7, CXCR5, and CXCR4. Multiple myeloma (MM) cells did not express CCR7 nor CXCR5 and did not migrate in response to their ligands; a moderate expression of CXCR4 on MM cells was accompanied by a migratory response to its ligand, CXCL12. By contrast, cells from B cell chronic lymphocytic leukemia (B-CLL) expressed the highest levels of these chemokine receptors and efficiently migrated in response to all ligands of CCR7, CXCR4, and CXCR5. In addition, the migration index of B-CLL cells in response to both of the CCR7 ligands correlated with the presence of clinical lymphadenopathy, thus indicating that the high expression of functional chemokine receptors justifies the widespread character of B-CLL, representing a clinical target for the control of tumor cell dissemination.

T cells kill bacteria captured by transinfection from dendritic cells and confer protection in mice.

Dendritic cells (DCs) phagocytose, process, and present bacterial antigens to T lymphocytes to trigger adaptive immunity. In vivo, bacteria can also be found inside T lymphocytes. However, T cells are refractory to direct bacterial infection, leaving the mechanisms by which bacteria invade T cells unclear. We show that T cells take up bacteria from infected DCs by the process of transinfection, which requires direct contact between the two cells and is enhanced by antigen recognition. Prior to transfer, bacteria localize to the immunological synapse, an intimate DC/T cell contact structure that activates T cells. Strikingly, T cells efficiently eliminate the transinfecting bacteria within the first hours after infection. Transinfected T cells produced high levels of proinflammatory cytokines and were able to protect mice from bacterial challenge following adoptive transfer. Thus, T lymphocytes can capture and kill bacteria in a manner reminiscent of innate immunity.