Effects of local cryotherapy on systemic endothelial activation, dysfunction, and vascular inflammation in adjuvant-induced arthritis (AIA) rats.

AIM: This study explored the systemic vascular effects of local cryotherapy with a focus on endothelial changes and arterial inflammation in the model of rat adjuvant-induced arthritis (AIA). METHODS: Cryotherapy was applied twice a day on hind paws of AIA rats from the onset of arthritis to the acute inflammatory phase. Endothelial activation was studied in the aorta by measuring the mRNA levels of chemokines (CXCL-1, MCP-1 (CCL-2), MIP-1α (CCL-3)) and adhesion molecules (ICAM-1, VCAM-1) by qRT-PCR. Endothelial dysfunction was measured in isolated aortic and mesenteric rings. Aortic inflammation was evaluated via the mRNA expression of pro-inflammatory cytokines (TNF-α, IL-6) by qRT-PCR and leucocyte infiltration analysis (flow cytometry). Plasma levels of TNF-α, IL-6, IL-1ß, IL-17A, and osteoprotegerin (OPG) were measured using Multiplex/ELISA. RESULTS: AIA was associated with an increased aortic expression of CXCL-1 and ICAM-1 as well as an infiltration of leucocytes and increased mRNA expression of IL-6, IL-1ß, and TNF-α. Local cryotherapy, which decreased arthritis score and structural damages, reduced aortic mRNA expression of CXCL-1, IL-6, IL-1ß, and TNF-α, as well as aortic infiltration of leucocytes (T lymphocytes, monocytes/macrophages, neutrophils) and improved acetylcholine-induced vasorelaxation in the aorta and mesenteric arteries. Plasma levels of IL-17A and OPG were significantly reduced by cryotherapy, while the number of circulating leucocytes was not. IL-17A levels positively correlated with endothelial activation and dysfunction. CONCLUSION: In the AIA model, local cryotherapy reduced systemic endothelial activation, immune cell infiltration, and endothelial dysfunction. Mechanistically, the reduction of circulating levels of IL-17A appears as the possible link between joint cooling and the remote vascular effects.

Human primary neutrophil mRNA does not contaminate human resolving macrophage mRNA after efferocytosis.

The ingestion of apoptotic corpses by macrophages, a process called efferocytosis, is a crucial step in inflammation resolution, since it alters macrophage phenotype toward a pro-resolving profile to foil inflammation and to favor tissue repair. Up to now, the resolving macrophages remain poorly characterized, especially in humans. Global investigations, like RNA sequencing, would be very helpful to unravel some features of these elusive cells. Nonetheless, these inquiries may be challenging in a single-species model, since the fate of ingested mRNA remains unknown and may hinder any subsequent mRNA investigations in the phagocyte. A full human model consisting of primary human neutrophil and primary human monocyte-derived macrophage co-culture was set up several decades ago to mimic in vitro the efferocytosis process. However, to our knowledge, this model has not been characterized as a suitable model to perform global mRNA investigations. Indeed, the extent of ingested neutrophil mRNA contamination has not been assessed in resolving macrophages. This work answers to this crucial question. Indeed, based on the protocols presented in this article, we demonstrate that neutrophil mRNA is severely degraded and is not able to cross-contaminate resolving macrophage mRNA, contrary to apoptotic human peripheral blood derived mononuclear cell (PBMC) or apoptotic leukemic Jurkat cell mRNA. Moreover, this allogenic co-culture system does not favor neither neutrophil activation nor macrophage pro-inflammatory cytokine release. Collectively, we highlight that this model of primary human neutrophil and primary human monocyte-derived macrophage co-culture is the best model for mRNA investigations in human resolving macrophages to help improving our knowledge on these crucial cells.

Local ice cryotherapy decreases synovial interleukin 6, interleukin 1ß, vascular endothelial growth factor, prostaglandin-E2, and nuclear factor kappa B p65 in human knee arthritis: a controlled study.

BACKGROUND: The aim of this study was to assess the anti-inflammatory effects of local cryotherapy in human non-septic knee arthritis. METHODS: In the phase I of the study, patients were randomized to receive either ice (30 min; N = 16) or cold CO2 (2 min; N = 16) applied twice during 1 day at an 8-h interval on the arthritic knee. In phase II, 16 other ice-treated arthritic knees according to the same protocol were compared to the contralateral non-treated arthritic knees (N = 16). The synovial fluid was analyzed just before the first cold application, then 24 h later. IL-6, IL-1ß, TNF-α, IL-17A, VEGF, NF-kB-p65 protein, and PG-E2 levels were measured in the synovial fluid and compared before/after the two cold applications. RESULTS: Forty-seven patients were included (17 gouts, 11 calcium pyrophosphate deposition diseases, 13 rheumatoid arthritides, 6 spondyloarthritides). Local ice cryotherapy significantly reduced the IL-6, IL-1ß, VEGF, NF-kB-p65, and PG-E2 synovial levels, especially in the microcrystal-induced arthritis subgroup, while only phosphorylated NF-kB-p65 significantly decreased in rheumatoid arthritis and spondyloarthritis patients. Cold CO2 only reduced the synovial VEGF levels. In the phase II of the study, the synovial PG-E2 was significantly reduced in ice-treated knees, while it significantly increased in the corresponding contralateral non-treated arthritic knees, with a significant inter-class effect size (mean difference - 1329 [- 2232; - 426] pg/mL; N = 12). CONCLUSIONS: These results suggest that local ice cryotherapy reduces IL-6, IL-1ß, and VEGF synovial protein levels, mainly in microcrystal-induced arthritis, and potentially through NF-kB and PG-E2-dependent mechanisms. TRIAL REGISTRATION: Clinicaltrials.gov, NCT03850392-registered February 20, 2019-retrospectively registered.

Antithymocytes globulins: Time to revisit its use in kidney transplantation?

T cell depletion by polyclonal antithymocyte globulins (ATG) has been used for many years in both organ and hematopoietic cell transplantation as an induction and rejection therapy. Nevertheless, its use remains largely empirical and many clinical questions, such as the determination of an individualized dose, therapeutic relevance of nondepletive effects, or prediction of long-term effects, are still unresolved. This review evaluates the evidence-based knowledge and the uncertainties concerning ATG, and suggests perspectives and opportunities for modern use of this old drug.

Fcγ receptor expression on splenic macrophages in adult immune thrombocytopenia.

Splenic macrophages play a key role in immune thrombocytopenia (ITP) pathogenesis by clearing opsonized platelets. Fcγ receptors (FcγR) participate in this phenomenon, but their expression on splenic macrophages and their modulation by treatment have scarcely been studied in human ITP. We aimed to compare the phenotype and function of splenic macrophages between six controls and 24 ITP patients and between ITP patients according to the treatments they received prior to splenectomy. CD86, human leucocyte antigen D-related (HLA-DR) and FcγR expression were measured by flow cytometry on splenic macrophages. The major FcγR polymorphisms were determined and splenic macrophage function was assessed by a phagocytosis assay. The expression of the activation markers CD86 and HLA-DR was higher on splenic macrophages during ITP compared to controls. While the expression of FcγR was not different between ITP and controls, the phagocytic function of splenic macrophages was reduced in ITP patients treated with intravenous immunoglobulin (IVIg) within the 2 weeks prior to splenectomy. The FCGR3A (158V/F) polymorphism, known to increase the affinity of FcγRIII to IgG, was over-represented in ITP patients. Thus, these are the first results arguing for the fact that the therapeutic use of IVIg during human chronic ITP does not modulate FcγR expression on splenic macrophages but decreases their phagocytic capabilities.

Pre-transplant end-stage renal disease-related immune risk profile in kidney transplant recipients predicts post-transplant infections.

BACKGROUND: End-stage renal disease (ESRD) is associated with premature aging of the T-cell system. Nevertheless, the clinical significance of pre-transplant ESRD-related immune senescence is unknown. METHODS: We studied whether immune risk phenotype (IRP), a typical feature of immune senescence, may affect post-transplant infectious complications. A total of 486 patients were prospectively studied during the first year post transplant. IRP was defined as positive cytomegalovirus serology with at least 1 of the following criteria: CD4/CD8 ratio <1 and/or CD8 T-cell count >90th percentile. RESULTS: We found that 47 patients (9.7%) had pre-transplant IRP. IRP+ patients did not differ from IRP- patients for any clinical characteristics, but exhibited more pronounced immune senescence. Both opportunistic infections (43% vs. 6%, P < 0.001) and severe bacterial infection (SBI) (40% vs. 25%, P = 0.028) were more frequent in IRP(+) patients. In multivariate analysis, IRP was predictive of both opportunistic infection (hazard ratio [HR] 2.97 [95% confidence interval {CI} 1.53-5.76], P = 0.001), and SBI (HR 2.33 [95% CI 1.34-3.92], P = 0.008). Acute rejection rates were numerically much lower in IRP+ patients. A total of 418 patients (86%) had biological evaluation 1 year post transplant. Among 41 IRP+ patients, 35 (85%) remained IRP+ 1 year post transplant. CONCLUSION: Pre-transplant IRP is associated with an increased risk of post-transplant infection.

Donor interleukin-22 and host type I interferon signaling pathway participate in intestinal graft-versus-host disease via STAT1 activation and CXCL10.

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation, limiting the success of this therapy. We previously reported that interleukin-22 (IL-22) participates to aGVHD development, but the underlying mechanisms of its contribution remain poorly understood. In this study, we analyzed the mechanism of the pathological function of IL-22 in intestinal aGVHD. Ex-vivo colon culture experiments indicated that IL-22 was able to induce Th1-like inflammation via signal transducer and activator of transcription factor-1 (STAT1) and CXCL10 induction in the presence of type I interferon (IFN). To evaluate a potential synergy between IL-22 and type I IFN in aGVHD, we transplanted recipient mice, either wild-type (WT) or type I IFN receptor deficient (IFNAR(-/-)), with bone marrow cells and WT or IL-22 deficient (IL-22(-/-)) T cells. We observed a decreased GVHD severity in IFNAR(-/-) recipient of IL-22(-/-) T cells, which was associated with a lower level of STAT1 activation and reduced CXCL10 expression in the large intestine. Finally, immunohistochemistry staining of STAT1 performed on gastrointestinal biopsies of 20 transplanted patients showed exacerbated STAT1 activation in gastrointestinal tissues of patients with aGVHD as compared with those without aGVHD. Thus, interfering with both IL-22 and type I IFN signaling may provide a novel approach to limit aGVHD.

ATG-induced accelerated immune senescence: clinical implications in renal transplant recipients.

Persistent ATG-induced CD4(+) T cell lymphopenia is associated with serious clinical complications. We tested the hypothesis that ATG induces accelerated immune senescence in renal transplant recipients (RTR). Immune senescence biomarkers were analyzed at transplant and one-year later in 97 incident RTR -62 patients receiving ATG and 35 receiving anti-CD25 mAb (α-CD25). This consisted in: (i) thymic output; (ii) bone marrow renewal of CD34(+) hematopoietic progenitor cells (CD34(+) HPC) and lymphoid (l-HPC) and myeloid (m-HPC) progenitor ratio; (iii) T cell phenotype; and (iv) measurement of T cell relative telomere length (RTL) and telomerase activity (RTA). Clinical correlates were analyzed with a 3 year follow-up. Thymic output significantly decreased one-year posttransplant in ATG-treated patients. ATG was associated with a significant decrease in l-HPC/m-HPC ratio. Late stage differentiated CD57(+) /CD28(-) T cells increased in ATG-treated patients. One-year posttransplant T cell RTL and RTA were consequently lower in ATG-treated patients. ATG is associated with accelerated immune senescence. Increased frequency of late differentiated CD4(+) T cell frequency at transplantation tended to be predictive of a higher risk of subsequent opportunistic infections and of acute rejection only in ATG-treated patients but this needs confirmation. Considering pretransplant immune profile may help to select those patients who may benefit from ATG to prevent severe infections and acute rejection.

Diagnosis and management of nocardiosis after bone marrow stem cell transplantation in adults: lack of lymphocyte recovery as a major contributing factor.

Hematopoietic cell transplantation (HCT) is a curative treatment for hematological malignancies. This therapeutic approach is associated with a profound immune deficiency and an increased rate of opportunistic infections. Nocardiosis is a rare bacterial infection occurring mainly in patients with deficient cell-mediated immunity, such as AIDS patients or transplant recipients. Diagnosis of nocardiosis can be challenging, as signs and symptoms are non-specific. Routine prophylaxis with trimethoprin/sulfamethoxazole (TMP/SMZ) does not prevent the risk of infection. Between May 2001 and December 2009, five cases of nocardiosis were diagnosed from the 366 allogeneic HCT recipients in our centre. Four patients developed a disseminated nocardiosis within the first year after HCT. The fifth patient presented a localized cutaneous nocardiosis. In disseminated cases, median total CD4+ T-cells were below 100 cells/µL. Naive CD4+ CD45RA+/RO- T-cells were almost undetectable. CD8(+) T-cells and NK cells were below the normal range and CD19+ B-cell reconstitution was completely deficient. In a localized case, we observed a lack of naive thymic emigrants CD4+ CD45RA+/RO- T-cells.

Can leg ulcer fibroblasts phenotype be influenced by human amniotic membrane extract?

Prevalence of leg ulcer in general population is important and new efficient treatments are now needed, especially for chronic leg ulcers. Human amniotic membrane (HAM) can be used as an alternative treatment for recalcitrant leg ulcers. The aim of this study is to investigate the effects of a HAM extract on normal fibroblasts (NF) and ulcer fibroblasts (UF). NF and UF were obtained from biopsies by explants technique. HAM extract was used at 10 µg of total proteins per ml. Single patient-matched NF and UF were compared, without or with HAM extract. Studied parameters were proliferation rate, retraction of free-floating lattices, alpha smooth muscle actin expression by flow cytometry, and synthesis of elastin, glycosaminoglycans (GAGs), pro-collagen I, MMP-1 and TIMP-1. Our results show that UF had a specific phenotype compared to NF: low proliferation, high expression of alpha-SM actin and high synthesis of MMP-1, TIMP-1 and elastin. HAM extract significantly increased the synthesis of GAGs, pro-collagen I and MMP-1 in NF and decreased retraction of free lattices. HAM extract transiently increased UF proliferation, slowed down lattices retraction and decreased elastin synthesis. In conclusion, HAM extract has little effect on UF for the parameters studied and NF are more responsive than UF. However, clinical beneficial effect of HAM application on leg ulcers was previously observed and might rather be related to an action on keratinocytes and/or a modulation of the highly inflammatory environment of these chronic wounds.

IL-22 deficiency in donor T cells attenuates murine acute graft-versus-host disease mortality while sparing the graft-versus-leukemia effect.

Acute graft-versus-host disease (aGVHD) remains a major complication following allogeneic hematopoietic cell transplantation (allo-HCT), limiting the success of this therapy. Many proinflammatory cytokines secreted following the conditioning regimen have been linked to aGVHD initiation. Interleukin-22 (IL-22) is a cytokine related to IL-10 for its structure and is secreted by T helper type 17 (TH17) cells and innate immune cells. Given the paradoxical role of IL-22 in inflammation with both protective or proinflammatory functions, we investigated whether IL-22 could have a role in aGVHD pathophysiology in a mouse allo-HCT model. In this study, we show that IL-22 deficiency in donor T cells can decrease the severity of aGVHD, while limiting systemic and local inflammation in aGVHD target organs. In addition, we found that Foxp3+ regulatory T cells (Treg cells) were increased in recipient mice that received IL-22-deficient T cells, suggesting that Treg were involved in the reduced severity of GVHD. Finally, we found that the graft-versus-leukemia (GVL) effect mediated by donor T cells was preserved in the absence of IL-22. Overall, these data suggest that targeting of IL-22 may represent a valid approach towards decreasing aGVHD severity after allo-HCT while preserving the GVL effect.

Subclinical Epstein-Barr virus viremia among adult renal transplant recipients: incidence and consequences.

The natural history and clinical significance of posttransplant Epstein-Barr virus (EBV) infection remain largely unknown. The aims of this study are to describe the incidence, risk factors and consequences of EBV infection after kidney transplantation. A total of 383 consecutive patients having received a kidney transplant between January 2002 and December 2010 were included. EBV polymerase chain reaction (PCR) was performed every 2 weeks for 3 months, and every 4 weeks for the next 9 months. A total of 155 of the 383 patients (40%) had at least one positive viremia during the first year posttransplant. The median time to viremia was day 31 posttransplant (14-329). A total of 73 (47%) had EBV viremia > 10(3) log and 23 (15%) had positive viremia for more than 6 months. EBV D+/R- patients (12/18 (67%) versus 143/365 (39%), p = 0.02) and those having received antithymocyte globulins (ATG) (54% vs. 35%; p<0.001) were more likely to develop EBV infection. EBV infection (hazard ratio [HR], 3.03; 95% confidence interval [CI], 1.72-8.29; p = 0.01) was associated with the occurrence of opportunistic infections. A positive EBV PCR during the first 6 months posttransplant was associated with graft loss (HR, 3.04; 95% CI, 1.36-6.79; p = 0.014). EBV reactivation is frequent after transplantation and reflects overimmunosuppression. Prospective studies should examine the association between EBV and graft loss.

Intravenous infusion of donor apoptotic leukocytes before transplantation delays allogeneic islet graft rejection through regulatory T cells.

AIM: This study describes the ability of intravenous donor apoptotic leukocyte infusion before islet transplantation to delay allogeneic graft rejection and implicates regulatory T cells (T(reg)) in the effect. METHODS: Allogeneic FVB (Friend virus B-type) islet transplants were placed under the kidney capsule of BALB/c recipient mice rendered diabetic by streptozotocin. Apoptotic donor leukocytes were infused intravenously 7 days before transplantation. Foxp3/DTR/GFP transgenic C57BL/6 mice were used as recipients to show depletion of T(reg) after apoptotic cell infusion. Control mice received islet transplants without apoptotic cells. RESULTS: The graft median survival time (MST) in recipient mice was 15±1.5 days when apoptotic cells were infused 7 days prior to transplantation of a 1000-islet-containing allograft and 6±0.5 days in the control mice (P<0.01). The same effect was observed using a 500-islet allograft, with an MST of 9±1.1 days vs. 3±0.8 days with and without (controls) apoptotic cells, respectively (P<0.01). This immunomodulatory effect was not observed when apoptotic cell administration was performed on the day of transplantation. Specific T(reg) depletion in Foxp3/DTR/GFP recipient mice inhibited the beneficial effect of apoptotic cell infusion with an MST of 8±1.5 days after apoptotic cell infusion vs. 2±0.2 days when T(reg) were depleted (P<0.01). Furthermore, T(reg) were specifically detected in the islet grafts of mice infused with apoptotic cells prior to islet transplantation. CONCLUSION: Infusion of donor apoptotic cells 7 days before allogeneic transplantation delays islet allograft rejection through a process involving T(reg).

Phosphatidylserine-expressing cell by-products in transfusion: A pro-inflammatory or an anti-inflammatory effect?

Labile blood products contain phosphatidylserine-expressing cell dusts, including apoptotic cells and microparticles. These cell by-products are produced during blood product process or storage and derived from the cells of interest that exert a therapeutic effect (red blood cells or platelets). Alternatively, phosphatidylserine-expressing cell dusts may also derived from contaminating cells, such as leukocytes, or may be already present in plasma, such as platelet-derived microparticles. These cell by-products present in labile blood products can be responsible for transfusion-induced immunomodulation leading to either transfusion-related acute lung injury (TRALI) or increased occurrence of post-transfusion infections or cancer relapse. In this review, we report data from the literature and our laboratory dealing with interactions between antigen-presenting cells and phosphatidylserine-expressing cell dusts, including apoptotic leukocytes and blood cell-derived microparticles. Then, we discuss how these phosphatidylserine-expressing cell by-products may influence transfusion.

Plasmacytoid dendritic cells and Th17 immune response contribution in gastrointestinal acute graft-versus-host disease.

The contribution of Th17 cells in acute graft-versus-host disease (aGVHD) has been demonstrated in aGVHD mouse models. However, their contribution in human gastrointestinal aGVHD remains unclear. We evaluated Th17 cells in a cohort of 23 patients at diagnosis of aGVHD. In this study, we have shown that the absolute number of Th17 cells using the CCR6 and CD161 markers were significantly higher in the intestinal mucosa of patients with aGVHD compared with intestinal mucosa of patients without aGVHD. Moreover, in keeping with the increase of CCR6+ and CD161+ T cells, RORγt the key transcription factor that orchestrates the differentiation of Th17 cells, was significantly increased in the intestinal mucosa of patients with aGVHD compared with intestinal mucosa of patients without aGVHD (P=0.01). Since plasmacytoid dendritic cells (PDCs) have been reported to drive the differentiation of the Th17 subset, we quantified PDCs in these patients. PDC CD123+ cells were increased in the intestinal mucosa of patients with aGVHD. Furthermore, the number of CD123+ PDCs paralleled the histological grade of aGVHD, providing evidence for a role of Th17-mediated responses and a potential new pathophysiological link between PDCs and Th17 in human aGVHD.

[Human amniotic membrane in the management of chronic venous leg ulcers]. / La membrane amniotique humaine dans la prise en charge des ulcères de jambe veineux chroniques.

BACKGROUND: The aim of our paper is to examine changes in the use of human amniotic membrane for venous leg ulcers through clinical studies and to present different models of tissue engineering employing human amniotic membrane for the purpose of future therapeutic use in wound healing. MATERIALS AND METHODS: This review is based on information obtained from a PubMed search using the following keywords "Amnion"[Mesh] AND "Leg Ulcer"[Mesh]; "Amnion"[Mesh] AND "Dermatology"[Mesh]. The selected articles are in English or French and deal with the sole use of human amniotic membrane in venous leg ulcers alone. RESULTS: Human amniotic membrane has a positive impact on chronic venous leg ulcers by promoting granulation tissue formation, reducing fibrosis and inducing re-epithelialisation. Nevertheless, further randomized clinical studies are needed. At the same time, tissue engineering models using human amniotic membrane may help to reduce wound healing time, thereby creating renewed interest in the use of human amniotic membrane. CONCLUSION: Considering its properties and the clinical studies analysed, human amniotic membrane could be useful in venous leg ulcer care.

Chemotherapy overcomes TRAIL-R4-mediated TRAIL resistance at the DISC level.

TNF-related apoptosis-inducing ligand or Apo2L (Apo2L/TRAIL) is a promising anti-cancer drug owing to its ability to trigger apoptosis by binding to TRAIL-R1 or TRAIL-R2, two membrane-bound receptors that are often expressed by tumor cells. TRAIL can also bind non-functional receptors such as TRAIL-R4, but controversies still exist regarding their potential to inhibit TRAIL-induced apoptosis. We show here that TRAIL-R4, expressed either endogenously or ectopically, inhibits TRAIL-induced apoptosis. Interestingly, the combination of chemotherapeutic drugs with TRAIL restores tumor cell sensitivity to apoptosis in TRAIL-R4-expressing cells. This sensitization, which mainly occurs at the death-inducing signaling complex (DISC) level, through enhanced caspase-8 recruitment and activation, is compromised by c-FLIP expression and is independent of the mitochondria. Importantly, TRAIL-R4 expression prevents TRAIL-induced tumor regression in nude mice, but tumor regression induced by TRAIL can be restored with chemotherapy. Our results clearly support a negative regulatory function for TRAIL-R4 in controlling TRAIL signaling, and unveil the ability of TRAIL-R4 to cooperate with c-FLIP to inhibit TRAIL-induced cell death.

Diagnosis and treatment of digestive cryptosporidiosis in allogeneic haematopoietic stem cell transplant recipients: a prospective single centre study.

Digestive cryptosporidiosis (DC) can mimic GVHD after allogeneic haematopoietic stem cell transplantation (HSCT), thus requiring a reduction of immunosuppressive drugs and a specific therapy, whereas GVHD requires an intensification of immunosuppression. We systematically searched for cryptosporidiosis by light microscopy, immunochromatography and PCR in HSCT recipients who presented with at least one episode of diarrhoea. Of 115 consecutive patients allografted between July 2006 and November 2008, we analysed stools in 52 of 56 patients meeting these criteria. We identified Cryptosporidium parvum in 5 of the 52 patients (9.6%) at a median of 503 days (range 20-790) after HSCT. In those five patients, the median CD4+ cell and B lymphocyte counts were 60/mm3 (0-234) and 0/mm3 (0-96), respectively. Two patients died of invasive fungal infections. In the other three patients, diarrhoea disappeared after a median of 5 weeks following onset of bitherapy with azithromycine and nitazoxanide; they were still alive 433, 380 and 1179 days after the DC diagnosis. DC is probably under diagnosed after HSCT because it is difficult to detect during the asymptomatic phase. Early bitherapy and reduction of immunosuppression seem efficacious. In our series, DC has a seasonal pattern and is promoted by profound T lymphopenia.