T-cell Immunodeficiency Research Articles

Foetal presentation of cartilage hair hypoplasia with extensive granulomatous inflammation

Cartilage-hair-hypoplasia is a rare autosomal recessive metaphyseal dysplasia due to RMRP (the RNA component of the RNase MRP ribonuclease mitochondrial RNA processing complex) gene mutations. So far, about 100 mutations have been reported in the promoter and the transcribed regions. Clinical characteristics include short-limbed short stature, sparse hair and defective cell-mediated immunity. We report herein the antenatal presentation of a female foetus, in whom CHH was suspected from 23 weeks' gestation, leading to a medical termination of the pregnancy at 34 weeks gestation, and thereafter confirmed by morphological and molecular studies. Post-mortem examination confirmed short stature and limbs, and revealed thymic hypoplasia associated with severe CD4 T-cell immunodeficiency along with extensive non caseating epithelioid granulomas in almost all organs, which to our knowledge has been described only in five cases. Molecular studies evidenced on one allele the most frequently reported founder mutation NR_003051: g.70A>G, which is present in 92% of Finnish patients with Cartilage Hair Hypoplasia. On the second allele, a novel mutation consisting of a 10 nucleotide insertion at position −18 of the promoter region of the RMRP gene (M29916.1:g.726_727insCTCACTACTC) was detected. The founder mutation was inherited from the father, and the novel mutation from the mother. To our knowledge, this case report represents the first detailed foetal analysis described in the literature.

T-Cell Reconstitution after Thymus Xenotransplantation Induces Hair Depigmentation and Loss

Here we present a mouse model for T-cell targeting of hair follicles, linking the pathogenesis of alopecia to that of depigmentation disorders. Clinically, thymus transplantation has been successfully used to treat T-cell immunodeficiency in congenital athymia, but is associated with autoimmunity. We established a mouse model of thymus transplantation by subcutaneously implanting human thymus tissue into athymic C57BL/6 nude mice. These xenografts supported mouse T-cell development. Surprisingly, we did not detect multiorgan autoimmune disease. However, in all transplanted mice, we noted a striking depigmentation and loss of hair follicles. Transfer of T cells from transplanted nudes to syngeneic black-coated RAG−/− recipients caused progressive, persistent coat-hair whitening, which preceded patchy hair loss in depigmented areas. Further transfer experiments revealed that these phenomena could be induced by CD4+ T cells alone. Immunofluorescent analysis suggested that Trp2+ melanocyte-lineage cells were decreased in depigmented hair follicles, and pathogenic T cells upregulated activation markers when exposed to C57BL/6 melanocytes in vitro, suggesting that these T cells are not tolerant to self-melanocyte antigens. Our data raise interesting questions about the mechanisms underlying tissue-specific tolerance to skin antigens.

Progressive Intracranial Fusiform Aneurysms and T-Cell Immunodeficiency

In the pediatric population, intracranial fusiform aneurysms have been associated with human immunodeficiency virus/acquired immunodeficiency syndrome and rarely with opportunistic infections related to other immunodeficiencies. The HIV virus and other infectious organisms have been implicated in the pathophysiology of these aneurysms. We present a child with T-cell immunodeficiency but no evidence of human immunodeficiency virus or opportunistic intracranial infections that developed progressive bilateral fusiform intracranial aneurysms. Our findings suggest a role of immunodeficiency or inflammation in the formation of some intracranial aneurysms.

Immunodeficiency in DiGeorge Syndrome and Options for Treating Cases with Complete Athymia

The commonest association of thymic stromal deficiency resulting in T-cell immunodeficiency is the DiGeorge syndrome (DGS). This results from abnormal development of the third and fourth pharyngeal arches and is most commonly associated with a microdeletion at chromosome 22q11 though other genetic and non-genetic causes have been described. The immunological competence of affected individuals is highly variable, ranging from normal to a severe combined immunodeficiency when there is complete athymia. In the most severe group, correction of the immunodeficiency can be achieved using thymus allografts which can support thymopoiesis even in the absence of donor-recipient matching at the major histocompatibility loci. This review focuses on the causes of DGS, the immunological features of the disorder, and the approaches to correction of the immunodeficiency including the use of thymus transplantation.

Inborn errors of human IL-17 immunity underlie chronic mucocutaneous candidiasis

Chronic mucocutaneous candidiasis (CMC) is characterized by recurrent or persistent symptomatic infection of the nails, skin and mucosae mostly by Candida albicans. CMC is common in patients with profound primary T-cell immunodeficiency, who often display multiple infectious and autoimmune diseases. Patients with syndromic CMC, including autosomal dominant hyper IgE syndrome (AD-HIES) and autosomal recessive autoimmune polyendocrinopathy syndrome type I (APS-I), display fewer other infections. Patients with isolated CMC (CMCD) rarely display any other severe disease. We review here recent progress in the genetic dissection of these three types of inherited CMC. Low IL-17 T-cell proportions were reported in patients with AD-HIES bearing heterozygous STAT3 mutations, prone to CMC and staphylococcal diseases, and in a kindred with autosomal recessive CARD9 deficiency, prone to CMC and other fungal infections. High levels of neutralizing autoantibodies against IL-17 cytokines were documented in patients with APS-I presenting with CMC as their only infectious disease. The first three genetic causes of CMCD were then reported: autosomal recessive IL-17RA and autosomal dominant IL-17F deficiencies and autosomal dominant STAT1 gain-of-function, impairing IL-17-producing T-cell development. Inborn errors of human IL-17 immunity underlie CMC. Impaired IL-17 immunity may therefore account for CMC in other settings, including patients with acquired immunodeficiency.

Raltegravir intensification shows differing effects on CD8 and CD4 T cells in HIV-infected HAART-suppressed individuals with poor CD4 T-cell recovery

Immunodiscordant HIV-infected patients show viral suppression during antiretroviral therapy but fail to recover CD4 T cells. Immunodiscordance is characterized by partial CD4 T-cell immunodeficiency and increased inflammation, activation and immunosenescence in both CD4 and CD8 T cells. A randomized, controlled, 48-week intensification study to assess the effect of raltegravir on immunological parameters in immunodiscordant patients (CD4 cell counts <350 cells/μl; viral load <50 copies/ml for >2 years). Patients were randomized (2 : 1) to intensify therapy with raltegravir (intensified arm, n = 30) or continue with the same therapy (control arm, n = 14). Both groups showed similar immunological baseline characteristics. CD4 T-cell counts increased faster in the intensified arm (P = 0.01, week 12). However, no differences between groups were observed at week 48. Additionally, no changes in thymic output (CD45RA(+)CD31(+) cells), activation (HLA-DR(+)CD95(+) cells) or ex-vivo cell death were observed in CD4 T cells at any time point intergroups or intragroups. Conversely, intensified arm showed significant decreases in the expression of the CD8 T-cell activation marker CD38 at weeks 24-48, which were more evident in memory cells. Despite this, the levels of HLA-DR expression in CD8 T cells and plasma soluble CD14 remained stable in both arms overtime. Long-term (48-week) raltegravir intensification failed to counterbalance CD4 T-cell deficiency and its associated features: hyperactivation and death of CD4 T cells. However, raltegravir induced a specific reduction of CD38 expression in CD8 T cells, suggesting a beneficial effect on CD8 T-cell hyperactivation, which has been linked with HIV-associated comorbidities.

Occurence of Malignancies in Patients with Primary Immunodeficiencies: An Analysis of the French Primary Immunodeficency Registry

AbstractAbstract 1057 Background:Primary immunodeficiencies (PID) are rare congenital disorders involving defects of the immune system. Aside from infectious complications, patients are at increased risk of malignant complications, which represent a leading cause of mortality in this context. The pathophysiology underlying malignant complications, especially lymphoid malignancies, in PID is not fully understood. The molecular mechansims of PID, that often involve lymphoid developent pathways, may also play a role in oncogenesis. A better understanding of the epidemiology of malignancies in PID may provide important insights in oncogenesis, particularly in lympomagenesis. Material and methods:French National Reference Center for Primary Immune Deficiencies (CEREDIH) has registered 4632 patients with PID as of July 2012. T-cell immunoficiencies and B-cell immodificencies reprensent 35.8% and 46.1% respectively. Patients with Ataxia-Telangiectasia and Severe Congenital Neutropenia were excluded frome the present analysis as they represent a more homogeneous group in terms of molecular pathophysiology and have been described elsewhere. T-cell immunodeficiencies comprise Severe combined immudoficiencies, Combined immunodeficiencies, other well defined T-cell immunoficiencies (including Wiskott-Aldrich Syndrome), and diseases of immune regulation (including X-linked lymphoproliferative disease and Autoimmune lymphoproliferative syndrome). B-cell immunodeficiencies include Agammaglobulinemia, Common Variable Immunodeficiency, Unspecified primary hypogammaglobulinemia, Selective IgA deficiency, Hyper-IgM symdrome and IgG subclass deficiency. Diagnostic class of PID, Age at diagnosis of PID, age at diagnosis of neoplastic complication, type of neoplasia, and survival were retrospectively colloected from the medical files. Non-melanomatous skin cancers and lymphoproliferative disorders occuring after allogeneic stem cell tranplantation were excluded from the analysis. Results:4632 patients with PID were analyzed. Two hundred and sixty seven patients developed 276 cancers (incidence 5.8%). One hundred and fifty seven patients developed lymphoid malignancies and 78 patients developed solid tumors (56.4% vs. 28.3% respectively). Compared to patients with B-cell PID, patients with T-cell PID had lower age at diagnosis of PID (5.5 [0–12.4] vs. 1.3–78]). Lymphoid malignancies, mainly high grade lymphomas were more prevalent in T-cell PID and PID diagnosed at a younger age (median age at diagnosis of PID for patients with lymphoid malignancies vs. solid tumors, 5.2 yr [0–85] and 37.5 [0–80] respectively, p<0,001). More than 75% of solid tumors occured in patients with B-cell PID with a median age of 45 yr. at diagnosis of cancer (p<0,001 compared to lymphoid malignancies for the entire cohort). Occurence of lymphoid malignancies had a major impact on mortality in patients with PID, with an overall survival (OS) of 24.7 yr [0.2–86] vs. 58.3 yr [0.2–90.8] for patients with solid tumors (p<0,001). The difference in OS between PID patients developing solid tumors was not statistically different than the whole cohort of PID patients. Both high and low-grade lymphomas were observed in patients with PID developing lymphoid malginancies. The majority of low grade-malignancies were oberserved in patients with B-cell PID. Discussion:PID bear a high risk of malignancies (5.8%). Solid tumors are observed mainly in B-cell PID and are diagnosed at an older age. Lymphoid malignancies are observed mainly in T-cell PID and B-cell PID diagnosed at a younger age, underlying a possible pathophysiological link between T-cell PID and a subset of B-cell PID. Disclosures:No relevant conflicts of interest to declare.

Upregulated TCRζ Enhances Interleukin-2 Production in T-Cells from Patients with CML

T-cell immunodeficiency is a common feature in patients with chronic myeloid leukemia (CML), and deficiency in CD3 levels was detected in T cells from these patients, which may represent a characteristic that is related to a lower T cell activation. In this study, we explored the possibility that forced TCRζ gene expression may upreg-u-late T cell receptor (TCR) signaling activation and reverse interleukin-2 (IL-2) production in T cells from patients with CML. A recombinant eukaryotic vector expressing TCRζ was transfected into T cells by nucleofection. Phosphorylated TCRζ, phosphorylated NF-κB, and the IL-2 level in TCRζ-transfected CD3+T cells that were activated with anti-CD3 and anti-CD28 antibodies were measured by Western blot and enzyme-linked immunosorbent assay (ELISA). Significantly increased TCRζ levels were found in TCRζ-transfected CD3+T cells. After CD3 and CD28 antibody stimulation, a significantly higher phosphorylated TCRζ chain level was demonstrated, and an increased IL-2 production in TCRζ-upregulated T cells was associated with the increased expression of the phosphorylated NF-κB. In conclusion, TCRζ gene transfection could restore TCRζ chain deficiency and enhance IL-2 production in T cells from patients with CML. It is possible that TCRζ chain reconstitution in leukemia-specific, clonally expanded T cells will effectively increase their activation of antileukemia cytotoxicity.

Primary T-cell immunodeficiency with immunodysregulation caused by autosomal recessive LCK deficiency

Signals emanating from the antigen T-cell receptor (TCR) are required for T-cell development and function. The T lymphocyte-specific protein tyrosine kinase (Lck) is a key component of the TCR signaling machinery. On the basis of its function, we considered LCK a candidate gene in patients with combined immunodeficiency. We identify and describe a child with a T-cell immunodeficiency caused by a homozygous missense mutation of the LCK gene (c.1022T>C) resulting from uniparental disomy. Genetic, molecular, and functional analyses were performed to characterize the Lck deficiency, and the associated clinical and immunologic phenotypes are reported. The mutant LCK protein (p.L341P) was weakly expressed with no kinase activity and failed to reconstitute TCR signaling in LCK-deficient T cells. The patient presented with recurrent respiratory tract infections together with predominant early-onset inflammatory and autoimmune manifestations. The patient displayed CD4(+) T-cell lymphopenia and low levels of CD4 and CD8 expression on the T-cell surface. The residual T lymphocytes had an oligoclonal T-cell repertoire and exhibited a profound TCR signaling defect, with only weak tyrosine phosphorylation signals and no Ca(2+) mobilization in response to TCR stimulation. We report a new form of T-cell immunodeficiency caused by a LCK gene defect, highlighting the essential role of Lck in human T-cell development and responses. Our results also point out that defects in the TCR signaling cascade often result in abnormal T-cell differentiation and functions, leading to an important risk factor for inflammation and autoimmunity.

Tetralogy of Fallot with Complete DiGeorge Syndrome: Report of a Case and a Review of the Literature

Complete DiGeorge syndrome (CDGS) has a severe T-cell immunodeficiency and is fatal without thymus or bone marrow transplantation. Associated congenital heart disease (CHD) further complicates the clinical management. We report an infant with tetralogy of Fallot, confluent and hypoplastic pulmonary arteries, right aortic arch, and aberrant left subclavian artery. He was athymic with no CD3+ T cells. CDGS was diagnosed with 22q11.2 deletion. The patient underwent central aortopulmonary shunt at 12 days of age. The patient died at 5 weeks of age awaiting thymus transplantation. We performed a review of the literature regarding CDGS and CHD. We found 43 cases including conotruncal defects (20) and nonconotruncal defects (23). The overall mortality rate was 67%. Among 30 cases undergoing transplantation (bone marrow 16 and thymus 12, bone marrow + thymus 2), the mortality rate was 53%. The patients with conotruncal defects were more likely to die before transplantation (45% vs. 16%, P =.04). The main cause of death was infection before and after transplantation. We conclude that children with CDGS and CHD have a high mortality. Bone marrow and thymus transplantation can improve the survival, but the overall management of these high risk patients remains challenging.

T-cell receptor excision circles and repertoire diversity in children with profound T-cell immunodeficiency

Approximately 40% of patients with profound T-cell immunodeficiency have no identified molecular basis. Early assessment of T-cell impairment is vital for medical intervention, if hematopoietic stem cell transplantation is needed. The dynamics of T-cell receptor excision circles (TRECs) revealing recent thymic output of naïve T cell and T-cell receptor (TCR) repertoire diversity reflecting broader responses to multiple antigens, are both important in resisting infections. The TRECs value and TCR repertoire diversity were evaluated from peripheral blood mononuclear cells in patients with primary severe T cell immunodeficiency, to elucidate the T-cell response. In seven children with <30% of normal phytohemagglutinin (PHA)-stimulated lymphocyte proliferation, including two IL2RG (Try74Gly and Arg226Lys, X-linked) and one RAG2 mutations [(Ser205Tyr) and (del 1366T, frameshift, 484stop); autosomal recessive], lower TRECs value and oligo- and restricted TCR diversity patterns, were associated with increased susceptibility to opportunistic infections, but not inversely correlated to the severity and frequency of infections. Three patients had successful cord blood stem cell transplantation which reconstructed the T cell immunodeficiency, with normalized TRECs value and TCR repertoire diversity at 6 months post-transplant, without clinical events. Low TRECs value and restricted TCR repertoire diversity can help in the early diagnosis of T cell immunodeficiency before irreversible sequelae and in the monitoring of post-transplantation T-cell immune reconstruction.

Defining combined immunodeficiency

Although the extreme condition of typical profound T-cell dysfunction (TD), severe combined immunodeficiency (SCID), has been carefully defined, we are currently in the process of better defining less typical T-cell deficiencies, which tend to present with autologous circulating T-cell combined immunodeficiency (CID). Because autologous cells might interfere with the outcome of bone marrow transplantation, protocols usually include conditioning regimens. Therefore it is important to define the numbers of autologous cells usually detected in patients with CID versus those with SCID. We sought to determine the number of circulating T cells in patients with SCID as opposed to those with CID, to study their function, and to evaluate their possible detection during newborn screening using T-cell receptor excision circle (TREC) analysis. Numbers of circulating CD3(+) T cells (as determined by means of flow cytometry), in vitro responses to PHA, and TREC levels, all measured at presentation, were compiled from the research charts of the entire cohort of patients followed prospectively for T-cell immunodeficiency at the Hospital for Sick Children. Clinical data were ascertained retrospectively from the patient's hospital charts. One hundred three patients had CD3(+) determinations, and 80 of them had a genetic diagnosis. All patients considered to have typical SCID had CD3(+) T-cell counts of fewer than 500 cells/μL. Some variability was observed among different genotypes. In vitro responses to PHA were recorded in 88 patients, of whom 68 had a genetic diagnosis. All patients with low CD3(+) T-cell numbers (<500 cells/μL) also had markedly decreased responses to PHA (typical SCIDs). However, responses ranged widely in the groups of patients with TD who had more than 500 CD3(+) autologous circulating T cells per microliter. Although patients with Omenn syndrome and ζ chain-associated protein, 70 kDa (ZAP70), and purine nucleoside phosphorylase (PNP) deficiencies had low responses, patients with the p.R222C mutation in the IL-2 receptor γ(IL2RG) gene as well as IL-10 receptor and CD40 ligand deficiencies had normal or near-normal mitogen responses. Finally, 51 patients had TREC levels measured. All patients with typical SCID, Omenn syndrome, and ZAP70 deficiency had low TREC levels. In contrast, patients with mutations in forkhead box protein 3 (FOXP3), CD40 ligand (CD40L), and IL-10 receptor α(IL10RA), as well as patients with the p.R222C mutation in the IL2RG gene, had normal TREC levels. Patients with typical SCID can be defined as having fewer than 500 circulating CD3(+) T cells. Most patients with autologous T cells still have profound TD, as defined by reduced in vitro function and thymus output. Some patients with conditions including TD have normal TREC levels and will therefore not be detected in a TREC-based newborn screening program.

T-cell immunodeficiency and reconstruction based on TCR rearrangement analysis in hematological malignancy: update from 2011 ASH annual meeting

Poor cellular immune function may relate to carcinogenic processes and to worse prognosis in solid tumor patients as well as in leukemia. Moreover, the progression of tumor might further induce the cellular immune suppression. Therefore, a set of molecular immunological techniques to analyze and monitor the changes of host T-cell immune status is needed, which can fully characterize the feature of T-cell immunodeficiency in different malignancies, providing information and direction for immune reconstruction, in particular for enhancement the specific anti-tumor immune function.

MST1 mutations in autosomal recessive primary immunodeficiency characterized by defective naive T-cell survival

AbstractThe molecular mechanisms that underlie T-cell quiescence are poorly understood. In the present study, we report a primary immunodeficiency phenotype associated with MST1 deficiency and primarily characterized by a progressive loss of naive T cells. The in vivo consequences include recurrent bacterial and viral infections and autoimmune manifestations. MST1-deficient T cells poorly expressed the transcription factor FOXO1, the IL-7 receptor, and BCL2. Conversely, FAS expression and the FAS-mediating apoptotic pathway were up-regulated. These abnormalities suggest that increased cell death of naive and proliferating T cells is the main mechanism underlying this novel immunodeficiency. Our results characterize a new mechanism in primary T-cell immunodeficiencies and highlight a role of the MST1/FOXO1 pathway in controlling the death of human naive T cells.

Expression feature of CD3, FcɛRIγ, and Zap-70 in patients with chronic lymphocytic leukemia

In leukemia patients, T-cell function has been suppressed with the disease progress. Patients with chronic lymphocytic leukemia (CLL) are all to a degree immunodeficient. In order to elucidate the feature of T-cell receptor signal transduction in CLL, the expression levels of CD3γ, δ, ɛ, and ζ chain, FcɛRIγ, and Zap-70 genes in peripheral blood mononuclear cells (PBMCs) were analyzed. Real-time polymerase chain reaction with SYBR Green technique was used for detecting the gene expression level in PBMCs from 13 patients with CLL, 13 healthy individuals, and 10 B-cell acute lymphocytic leukemia (B-ALL) served as control. The β2-microglobulin gene was used as an endogenous reference. Relative mRNA expression level of genes was analyzed by using the 2−ΔCt × 100% method. Significant lower expression levels of CD3γ, ɛ, and ζ chain genes, as well as FcɛRIγ gene were found in CLL samples. Moreover, there was lost the negative correlation of the expression levels between CD3ζ and FcɛRIγ genes. The expression level of Zap-70 in CLL was lower than those from healthy controls, while higher than those from B-ALL group. There was no significant correlation between the expression levels of CD3ζ and Zap-70 genes neither in the healthy group nor in the CLL group. In conclusion, the results provide a global gene expression profile of CD3γ, δ, ɛ, and ζ chains, and the CD3ζ-related genes FcɛRIγ and Zap-70 in CLL. Deficiency of these gene expression levels might represent the feature related to T-cell immunodeficiency. The study might contribute to better understand the cellular immune features in CLL patients.

Autoimmune Dysregulation and Purine Metabolism in Adenosine Deaminase Deficiency

Genetic defects in the adenosine deaminase (ADA) gene are among the most common causes for severe combined immunodeficiency (SCID). ADA-SCID patients suffer from lymphopenia, severely impaired cellular and humoral immunity, failure to thrive, and recurrent infections. Currently available therapeutic options for this otherwise fatal disorder include bone marrow transplantation (BMT), enzyme replacement therapy with bovine ADA (PEG-ADA), or hematopoietic stem cell gene therapy (HSC-GT). Although varying degrees of immune reconstitution can be achieved by these treatments, breakdown of tolerance is a major concern in ADA-SCID. Immune dysregulation such as autoimmune hypothyroidism, diabetes mellitus, hemolytic anemia, and immune thrombocytopenia are frequently observed in milder forms of the disease. However, several reports document similar complications also in patients on long-term PEG-ADA and after BMT or GT treatment. A skewed repertoire and decreased immune functions have been implicated in autoimmunity observed in certain B-cell and/or T-cell immunodeficiencies, but it remains unclear to what extent specific mechanisms of tolerance are affected in ADA deficiency. Herein we provide an overview about ADA-SCID and the autoimmune manifestations reported in these patients before and after treatment. We also assess the value of the ADA-deficient mouse model as a useful tool to study both immune and metabolic disease mechanisms. With focus on regulatory T- and B-cells we discuss the lymphocyte subpopulations particularly prone to contribute to the loss of self-tolerance and onset of autoimmunity in ADA deficiency. Moreover we address which aspects of immune dysregulation are specifically related to alterations in purine metabolism caused by the lack of ADA and the subsequent accumulation of metabolites with immunomodulatory properties.

Screening newborns for primary T-cell immunodeficiencies: consensus and controversy

Newborn screening for early identification of T-cell lymphopenia and severe combined immunodeficiency has recently been recommended as an addition to the newborn screening programs in all states. This article will review the evidence supporting the use of this newborn screening test, and will outline the barriers to nationwide implementation, which include issues specific to this test and controversies regarding newborn screening in general.

Multi-focal EBV-mucocutaneous ulcer heralding late-onset T-cell immunodeficiency in a woman with lupus erythematosus

Epstein Barr virus (EBV)-positive mucocutaneous ulcer (MCU) is a new clinicopathologic entity with a self-limited indolent course, and responds well to conservative management [1]. These are invariably localized (60% in oropharyngeal area) and may occur in patients with senile or iatrogenic immunosuppression. Lesions typically regress with reduction in immunosuppression, but may recur. Prognosis is always favorable. We report a unique case of multifocal EBV-related MCU as the first manifestation of an unsuspected T-cell immunodeficiency. A 45-year-old woman had been treated with azathioprine and steroids for lupus nephritis and encephalitis from age 20. Her medications were stopped for 10 years. She presented with mycobacterium avium intracellulare (MAI) lymphadenopathy of groin and was treated with ethambutol, clarithromycin and rifampicin. Six months later, she suffered from left facial palsy, molluscum contagiosum (Fig. 1a) and a gum lesion (Fig. 1b). Positron emission tomography (PET) scanning showed uptake in left ear, lung, and gum (SUVmax 1.5–5.0) (Fig. 1c). A biopsy (Fig. 1d, e) showed a dense lymphoid infiltrate positive for CD20 (L26), CD30 (BerH2), and EBER. This was compatible with EBV-related mucocutaneous lymphoproliferation [1]. Antibodies to human immunodeficiency virus (HIV) and human T-cell lymphotropic virus (HTLV-1) and autoimmune markers were negative, but her CD4 (76 L/lL, normal 354–1,526) and CD8 counts (71 L/lL, normal 318–1,458) were severely depressed, with normal B and NK cell numbers. Cytogenetic study showed mosiac 46, XX, delXq27 [5]/46, XX [59]. In view of likely persistent low T-cell counts, disseminated lesions, and functional deficit, she was treated with rituximab (375 mg/ m 9 8) [2] with a complete metabolic response and partial facial nerve recovery. The CD4 and CD8 counts remained depressed at 2 years and she refused further genetic tests or family studies. We report the first case of multifocal EBV-related MCU in an adult patient with multiple opportunistic infections due to cellular immune defect. In HIV patients, molluscum contagiosum and MAI infections occur when the CD4 count falls near 50 L/lL [3], and both are rare in acquired T-cell immunodeficiency cases. Late-onset T-cell immunodeficiency (10% of cases and up to age 64) is increasingly recognized [4]. Over 20% of late-onset immunodeficiencies had lymphoma and autoimmune manifestations [4]. Patients with genetic T-cell defects are genetically heterogeneous ([150 disorders described). Intriguingly, our case carries a mosaic chromosome X cytogenetic defect. Iatrogenic immunodeficiency is also possible, but her therapy had been stopped many years ago, and her SLE is likely secondary to her T-cell dysregulation [5]. Irrespective of the underlying predisposition, in patients with unexplained sequential opportunistic infections and malignancies, a full work-up for immunodeficiency is needed. W. Y. Au (&) Department of Medicine, UMU, 4/F, Professorial Block, Queen Mary Hospital, Pokfulam Road, Hong Kong, Hong Kong e-mail: auwing@hotmail.com

Disseminated fusariosis in immunocompromised patients

Immunocompromised patients are at high risk of developing serious disseminated infections by opportunistic fungi (Aspergillus, Candida, and Fusarium spp), which frequently present as cutaneous lesions, sometimes as a first sign. Prolonged and deep neutropenia, immunodepressive treatments (systemic steroids and chemotherapy) and severe T-cell immunodeficiency are the most important risk factors. We report 2 patients with acute lymphoblastic leukemia, who developed multiple tender erythematous skin lesions on their legs and arms during chemotherapy treatment. Skin biopsies for histology and culture studies established the diagnosis of Fusarium infection. They received treatment with systemic antifungal and granulocyte colony-stimulting factor. The infection responded after recovering from neutropenia. Early diagnosis and treatment is very important to improve the prognosis, because these infections in immunodepressed hosts have a high mortality rate.

Autonomous and extrinsic regulation of thymopoiesis inhuman immune system (HIS) mice

Human Immune System (HIS) mice represent a novel biotechnology platform to dissect human haematopoiesis and immune responses. However, the limited human T-cell development that is observed in HIS mice restricts its utility for these applications. Here, we address whether reduced thymopoiesis in HIS mice reflects an autonomous defect in T-cell precursors and/or a defect in the murine thymic niche. Human thymocyte precursors seed the mouse thymus and their reciprocal interactions with murine thymic epithelial cells (TECs) led to both T-cell and TEC maturation. The human thymocyte subsets observed in HIS mice demonstrated survival, proliferative and phenotypic characteristics of their normal human counterparts, suggesting that the intrinsic developmental program of human thymocytes unfolds normally in this xenograft setting. We observed that exogenous administration of human IL-15/IL-15Rα agonistic complexes induced the survival, proliferation and absolute numbers of immature human thymocyte subsets, without any obvious effect on cell-surface phenotype or TCR Vβ usage amongst the newly selected mature single-positive (SP) thymocytes. Finally, when IL-15 was administered early after stem cell transplantation, we noted accelerated thymopoiesis resulting in the more rapid appearance of peripheral naïve T cells. Our results highlight the functional capacity of murine thymic stroma cells in promoting human thymopoiesis in HIS mice but suggest that the "cross-talk" between murine thymic stroma and human haematopoietic precursors may be suboptimal. As IL-15 immunotherapy promotes early thymopoiesis, this novel approach could be used to reduce the period of T-cell immunodeficiency in the post-transplant clinical setting.