Chowdhary, Vaidehi

Abstract Background/Purpose Interferon (IFN) gene expression signatures have been observed in whole blood and mixed immune cell populations in systemic lupus erythematosus (SLE), but the significance of this IFN signaling in immune cell subsets is not well understood. We examined gene expression in individual SLE patient monocytes to explore the impact of increased IFN-induced transcription in single cells. Methods CD14++CD16- classical monocytes and CD14dimCD16+ non classical monocytes from SLE patients were purified by magnetic separation. Single cells were isolated, and gene expression in each individual cell was examined by rtPCR. Results Monocytes from the same SLE patient blood sample demonstrated varying levels of IFN-induced gene expression. In classical monocytes, high IFN score correlated with CD32a, IL1B, and IL8 expression. In non-classical monocytes, high IFN score was correlated with a larger number of inflammatory mediators, including cytokines such as IL12, IL23, and IL15; the immune receptors CD36, CD32a, CD80, and TLR7; and inflammatory signaling genes such as RELA, STAT2, IRAK1, IRAK4, and MyD88. ConclusionWe observed striking diversity in the IFN responses of individual monocytes, demonstrating that IFN signaling has distinct effects upon classical and non-classical monocytes. Single cell studies can reveal effects of IFN on single immune cells and uncommon populations such as non-classical monocytes, which would be masked in whole blood or mixed cell populations.

Abstract CD4 and CD8 coreceptors play an important role in the development and maturation of αβ TCR+ T cells. However, T cells lacking CD4 and CD8 (double negative T or DNT cells) are present in the periphery and are significantly expanded in systemic lupus erythematosus (SLE) and Sjogren’s syndrome. The antigens that cause expansion of these DNT cells are unknown. As T cell activation by superantigens does not require coreceptors, we hypothesized that superantigens could activate DNT cells and contribute to autoimmunity. HLA-DQ8 and HLA-DR3 transgenic mice lacking both CD4 and CD8 were generated by intercrossing CD4 and CD8 single knockout mice. The CD4.CD8 double knockout (DKO) mice harbored a diverse repertoire of DNT cells in the periphery, albeit at reduced numbers compared to wild type (WT) mice. DNT cells from DKO mice responded robustly to the superantigen, staphylococcal enterotoxin B, but not to HLA restricted conventional antigens. Implantation of mini-osmotic pumps delivering 10 or 50 μg of SEB continuously over 7 or 28 days induced a lupus-like disease in WT as well as DKO DR3 and DQ8 mice. However, the immunopathology was significantly more pronounced in DKO mice. Immunostaining revealed extensive infiltration of multiple organs including lungs, liver and kidneys with CD3+ T cells in DKO mice. Overall, our study unraveled the role of CD4 and CD8 coreceptors in T cell development/function and the role of superantigens and DNT cells in the pathogenesis of lupus.

AbstractAimEosinophilic fasciitis (EF) is a rare, fibrosing disorder of skin and subcutaneous tissue. This study was undertaken to describe its clinical and laboratory features and identify prognostic factors associated with outcome.MethodsWe conducted a retrospective review of all EF patients evaluated at our institution from 1 January1997 to 30 December 2016. Kaplan‐Meier methods were used to determine treatment response rates over time. Potential associations between baseline characteristics and complete response were examined using Cox models adjusted for age and sex. Time‐dependent covariates were used to examine treatment effects.ResultsWe identified 89 EF patients, with a female‐to‐male ratio of 1:1. Clinical features included groove sign in 26 (29%), peau d'orange/dimpling in 22 (25%), inflammatory arthritis in 9 (10%) and muscle weakness in 9 (10%). Aldolase was elevated in 11/36 (31%). Complete response rate was 60% (95% confidence interval [CI]: 35‐75) at 3 years. Diagnostic delay was inversely associated with treatment response (hazards ratio: 0.84 per 1 month increase; 95% CI: 0.73‐0.98). No baseline characteristics correlated with treatment response, but a trend toward positive association of elevated aldolase, hypergammaglobulinemia and presence of hematologic disorders was noted. Methotrexate was the most commonly used immunosuppressant in 79%, hydroxychloroquine in 45%, mycophenolate mofetil in 18% and azathioprine in 8%. No single immunosuppressant agent was associated with a superior response during treatment.ConclusionsEF is characterized by relatively high response rates. Consensus diagnostic criteria, standardized management algorithms, and large prospective multi‐center cohorts are needed to develop an evidence‐directed approach to this challenging condition.

ObjectiveType I interferon (IFN) is important to systemic lupus erythematosus (SLE) pathogenesis, but it is not clear how chronic elevations in IFN alter immune function. We compared cytokine responses after whole blood stimulation with Toll‐like receptor (TLR) agonists in high‐ and low‐IFN SLE patient subgroups.MethodsSLE patients and nonautoimmune controls were recruited, and SLE patients were categorized as either high or low IFN. Whole blood was dispensed into tubes coated with lipopolysaccharide (LPS), oligonucleotides with cytosine‐guanine repeats, Resiquimod, IFN‐α, and IFN‐α + LPS. Cytokine production in patient sera and after whole blood TLR stimulation was measured by multiplex assay, and type I IFN was assessed using a functional assay.ResultsCirculating plasmacytoid dendritic cell numbers were specifically reduced in high‐IFN SLE patients and not in low‐IFN SLE patients. In serum, we observed that the correlations between cytokines in serum differed to a much greater degree between the high‐ and low‐IFN groups (P < 0.0001) than the absolute cytokine levels differed between these same groups. In stimulated conditions, the high‐IFN patients had less cytokine production in response to TLR ligation than the low‐IFN SLE patients. LPS produced the most diverse response, and a number of interactions between type I IFN and LPS were observed.ConclusionWe find striking differences in resting and stimulated cytokine patterns in high‐ vs. low‐IFN SLE patients, which supports the biological importance of these patient subsets. These data could inform personalized treatment approaches and the pathogenesis of SLE flare following infection.

ObjectiveSystemic lupus erythematosus (SLE) is frequently characterized by activation of the type I interferon (IFN) pathway. We previously observed that a missense single‐nucleotide polymorphism (rs1049564) in the purine nucleoside phosphorylase (PNP) gene was associated with high levels of IFN in SLE. PNP is a key enzyme involved in purine metabolism. In this study, we performed functional follow‐up of this polymorphism in human cells.MethodsType I IFN was measured in patient sera, using a reporter cell assay. Structural modeling of the PNP variant was performed using PyMOL software. PNP messenger RNA (mRNA) and protein levels and type I IFN–induced gene expression were measured in lymphoblastoid cell lines with known PNP rs1049564 genotypes. The cell cycle was assayed using flow cytometry.ResultsStructural modeling indicated no major disruption in folding related to rs1049564. We observed that homozygous rs1049564 TT lymphoblastoid cells had decreased PNP mRNA expression and protein levels, and that cells with the TT genotype had reduced PNP enzymatic activity even when the amount of PNP was controlled. Cells with the TT genotype had a 2‐fold increase in S‐phase block as compared with cells with the homozygous CC phenotype. The S‐phase block could be pharmacologically reversed with hypoxanthine and adenosine, supporting the notion that relative PNP deficiency is the cause of the S‐phase block. Type I IFN–induced transcripts were increased in a dose‐response manner related to the rs1049564 T allele, at both baseline and after type I IFN stimulation.ConclusionThe PNP rs1049564 T allele is a loss‐of‐function variant that induces S‐phase block and IFN pathway activation in lymphocytes. The S‐phase block could be rescued in our in vitro experiments, suggesting the potential for personalized treatment.

Objectives Important findings can be masked in gene expression studies of mixed cell populations. We examined single-cell gene expression in SLE patient monocytes in the context of clinical and immunological features. Methods Monocytes were purified from patients with SLE and controls, and individually isolated for single-cell gene expression measurement. A panel of monocyte-related transcripts were measured in individual classical (CL) and non-classical (NCL) monocytes. Results Analyses of both CL and NCL monocytes demonstrated that many genes had a lower expression rate in SLE monocytes than in controls. Unsupervised hierarchical clustering of the CL and NCL data sets demonstrated independent clusters of cells from the patients with SLE that were related to disease activity, type I interferon (IFN) and medication use. Thus, each of these factors exerted a different impact on monocyte gene expression that could be identified separately, and a number of genes correlated uniquely with disease activity. We found within-cell correlations between genes directly induced by type I IFN-induced and other non–IFN-induced genes, suggesting the downstream biological effects of type I IFN in individual human SLE monocytes which differed between CLs and NCLs. Conclusions In summary, single-cell gene expression in monocytes was associated with a wide range of clinical and biological features in SLE, providing much greater detail and insight into the cellular biology underlying the disease than previous mixed-cell population studies.

Abstract Mature peripheral double negative T (DNT) cells expressing αβ TCR but lacking CD4/CD8 coreceptors play protective as well as pathogenic roles. To better understand their development and functioning in vivo, we concomitantly inactivated CD4 and CD8 genes in mice with intact MHC class I and class II molecules with the hypothesis that this would enable the development of DNT cells. We also envisaged that these DNT cells could be activated by bacterial superantigens in vivo as activation of T cells by superantigens does not require CD4 and CD8 coreceptors. Because HLA class II molecules present superantigens more efficiently than murine MHC class II molecules, CD4 CD8 double knockout (DKO) mice transgenically expressing HLA-DR3 or HLA-DQ8 molecules were generated. Although thymic cellularity was comparable between wild type (WT) and DKO mice, CD3+ αβ TCR+ thymocytes were significantly reduced in DKO mice, implying defects in thymic-positive selection. Splenic CD3+ αβ TCR+ cells and Foxp3+ T regulatory cells were present in DKO mice but significantly reduced. However, the in vivo inflammatory responses and immunopathology elicited by acute challenge with the staphylococcal superantigen enterotoxin B were comparable between WT and DKO mice. Choric exposure to staphylococcal enterotoxin B precipitated a lupus-like inflammatory disease with characteristic lympho-monocytic infiltration in lungs, livers, and kidneys, along with production of anti-nuclear Abs in DKO mice as in WT mice. Overall, our results suggest that DNT cells can develop efficiently in vivo and chronic exposure to bacterial superantigens may precipitate a lupus-like autoimmune disease through activation of DNT cells.

AbstractToxic shock syndrome toxin‐1 (TSST‐1) is a potent superantigen produced by Staphylococcus aureus. In addition to menstrual and nonmenstrual toxic shock syndromes, TSST‐1 is also implicated in the immunopathogenesis of pneumonia, infective endocarditis, neonatal exanthematous disease, and atopic dermatitis among others. Superantigens first bind to major histocompatibility complex (MHC) class II molecules and then activate a large proportion of T cells by cross‐linking their T cell receptor. As binding to MHC class II molecules is a critical step in the robust activation of the immune system by TSST‐1 and other superantigens, polymorphic variations between different HLA‐DR alleles could potentially influence the magnitude of immune activation and immunopathology caused by TSST‐1. As TSST‐1 is highly toxic to humans and given that multiple variations of alleles of HLA‐DR and HLA‐DQ are expressed in each individual, it is difficult to determine how HLA‐DR polymorphisms quantitatively and qualitatively impact immune activation caused by TSST‐1 in humans. However, such investigations can be conducted on transgenic mice lacking all endogenous MHC class II molecules and expressing specific HLA class II alleles. Therefore, transgenic mice expressing different HLA‐DRB1 alleles (HLA‐DRB1*15:01, HLA‐DRB1*15:02, HLA‐DRB1*03:01, HLA‐DRB1*04:01), and sharing HLA‐A1*01:01 chain, were systemically challenged with purified TSST‐1 and multiple immune parameters were assessed. Among the HLA‐DR alleles, mice expressing HLA‐DRB1*15:01 allele elicited a significantly higher serum cytokine/chemokine response; greater splenic T cell expansion and most severe organ pathology. Our study highlights the potential utility of human leukocyte antigen (HLA) transgenic mice in understanding the impact of HLA polymorphisms on the outcomes of diseases caused by TSST‐1 and other superantigens.