Restriction of T-cell receptor repertoires in idiopathic CD4+ lymphocytopenia

Successful Cord Blood Transplantation for Idiopathic CD4+ Lymphocytopenia

Idiopathic CD4+ lymphocytopenia (ICL) is the depletion of CD4+ lymphocytes to <300 cells/mm3 without human immunodeficiency virus infection or other causes of lymphocytopenia. ICL causes fatal infections; its etiology remains unclear and it lacks consensus regarding therapeutic options. We report the first patient with ICL who had a successful clinical course following a cord blood transplant (CBT). A 45-year-old woman was diagnosed with ICL and underwent partial hepatectomy for an abscess caused by the Mycobacterium avium complex. No specific gene alterations were detected through next generation sequencing-based evaluation. Following a reduced-intensity conditioning (RIC) regimen consisting of fludarabine, busulfan, and 4 Gy total body irradiation, a single-unit CBT was performed. Neutrophils were engrafted on day +14. CD4+ lymphocyte counts increased to over 300 cells/mm3 on day +436. After 75 months, she was alive without any sequelae. CBT with an RIC regimen could be a curable treatment option for ICL.

Idiopathic CD4 Lymphocytopenia: Current Insights

Idiopathic CD4 lymphocytopenia is a condition characterized by low CD4 counts. It is rare and most of the information about this illness comes from case reports. Presentation is usually in the 4th decade of life with opportunistic infections, autoimmune disease or neoplasia. The pathophysiology of this condition is not well understood. Management revolves around treatment of the presenting condition and close follow-up of these patients. This review presents a narrative summary of the current literature on idiopathic CD4 lymphocytopenia.

Humanized mouse models reveal an immunologic classification of idiopathic CD4 lymphocytopenia subtypes

Idiopathic CD4 lymphocytopenia (ICL) is a clinically heterogeneous immunodeficiency disorder defined by low numbers of circulating CD4+ T cells and increased susceptibility to opportunistic infections. CD8+ T cells, NK, and/or B cells may also be deficient in some patients. To delineate possible pathogenic cellular mechanisms in ICL, we compared immune system development and function in NOD-RAGKO-γcKO (NRG) mice transplanted with hematopoietic stem cells from patients with ICL or healthy controls. CD34+ hematopoietic stem cells from healthy controls and patients with ICL reconstituted NRG mice equally well. In contrast, PBMC transfers into NRG mice identified 2 ICL engraftment phenotypes, reconstituting and nonreconstituting (NR), based on the absence or presence of donor lymphopenia. For patients in the NR group, the distribution of lymphocyte subsets was similar in the peripheral blood of both the patient and the corresponding humanized mice. The NR-ICL group could be further divided into individuals whose CD3+ T cells had defects in proliferation or survival. Thus, ICL cellular pathogenesis might be classified by humanized mouse models into 3 distinct subtypes: (a) T cell extrinsic, (b) T cell intrinsic affecting proliferation, and (c) T cell intrinsic affecting survival. Humanized mouse models of ICL help to delineate etiology and ultimately to guide development of individualized therapeutic strategies.

Idiopathic lymphocytopenia

PURPOSE OF REVIEW

Idiopathic CD4⁺ lymphocytopenia (ICL) is defined by the reduction of the main lymphocyte subtype in peripheral blood and CD4⁺ T cells below 300/μl in the absence of any secondary known causes of lymphopenia, including viral causes. The present review aims to state the latest available data on clinical, pathological and therapeutic aspects related to ICL, published from 1990 to 2014. The last observed clinical presentation and complications of ICL patients are described. The latest findings and possible mechanisms involved in the development of ICL features are included in the present review; however, pathogenesis of ICL has remained mainly obscured. Finally, recent therapeutic efforts considered in ICL patients are discussed.

RECENT FINDINGS

In spite of the serious complications ICL has on the patients' quality of life, data on clinical, etiopathological and therapeutic behavior for ICL are very limited. On one side, an abnormal blood cell count may be the sole presentation; however, occurrence of disseminated malignant tumors is not uncommon in patients. Recent findings highlight the role of cytokines, especially interleukin-2, on features such as phenotype severity and responsiveness of the condition to therapy. In addition, some studies have suggested that a defect in hematopoietic stem cells may be involved in disease progression, an idea that is supported by the success of bone marrow transplantation in acquiring persistent remissions in ICL patients.

SUMMARY

ICL is a hematologic condition of increasing importance due to its diverse clinical and pathological spectrum. Molecular studies have shown the presence of mutations involved in lymphocyte development as potential factors that may contribute to ICL occurrence. ICL patients could present either with common infections or really serious malignant conditions. The role of cytokines, especially interleukin-2, has emerged as one of the main possible mechanisms involved in clinical and pathological behavior of ICL. Today, the main therapeutic approaches are controlling life-threatening infections and underlying disorders along with efforts to cure ICL through rising CD4⁺ cell counts using cytokine interventions and transplantation.

Idiopathic CD4 Lymphocytopenia: Spectrum of opportunistic infections, malignancies, and autoimmune diseases

Idiopathic CD4 lymphocytopenia (ICL) was first defined in 1992 by the US Centers for Disease Control and Prevention (CDC) as the repeated presence of a CD4+ T lymphocyte count of fewer than 300 cells per cubic millimeter or of less than 20% of total T cells with no evidence of human immunodeficiency virus (HIV) infection and no condition that might cause depressed CD4 counts. Most of our knowledge about ICL comes from scattered case reports. The aim of this study was to collect comprehensive data from the previously published cases to understand the characteristics of this rare condition. We searched the PubMed database and Science Direct for case reports since 1989 for Idiopathic CD4 lymphocytopenia cases. We found 258 cases diagnosed with ICL in 143 published papers. We collected data about age, sex, pathogens, site of infections, CD4 count, CD8 count, CD4:CD8 ratio, presence of HIV risk factors, malignancies, autoimmune diseases and whether the patients survived or died. The mean age at diagnosis of first opportunistic infection (or ICL if no opportunistic infection reported) was 40.7 ± 19.2 years (standard deviation), with a range of 1 to 85. One-sixty (62%) patients were males, 91 (35.2%) were females, and 7 (2.7%) patients were not identified whether males or females. Risk factors for HIV were documented in 36 (13.9%) patients. The mean initial CD4 count was 142.6 ± 103.9/mm³ (standard deviation). The mean initial CD8 count was 295 ± 273.6/mm³ (standard deviation). The mean initial CD4:CD8 ratio was 0.6 ± 0.7 (standard deviation). The mean lowest CD4 count was 115.4 ± 87.1/mm³ (standard deviation). The majority of patients 226 (87.6%) had at least one infection. Cryptococcal infections were the most prevalent infections in ICL patients (26.6%), followed by mycobacterial infections (17%), candidal infections (16.2%), and VZV infections (13.1%). Malignancies were reported in 47 (18.1%) patients. Autoimmune diseases were reported in 37 (14.2%) patients.

Peptide library-based evaluation of T-cell receptor breadth detects defects in global and regulatory activation in human immunologic diseases

The ability of T-cells to respond to foreign antigens and to appropriately regulate this response is crucial for maintaining immune homeostasis. Using combinatorial peptide libraries, we functionally measured broad T-cell reactivity and observed impaired reactivity in established models of T-cell receptor repertoire restriction and in previously unrecognized disease contexts. By concurrently analyzing T-regulatory and T-effector cells, we show strong functional correlation between these subsets in healthy individuals and, strikingly, that alterations of this balance are associated with T helper type 2 (Th2)-mediated disease in a lymphopenic setting. Finally, we demonstrate that peptide-based priming of polyclonal naive cells with relatively low concentrations skews toward Th2 differentiation. These findings provide unique insight into the pathophysiology and functional consequences of abnormal T-cell repertoires and into differentiation of human naive T-cells.

Idiopathic CD4 lymphocytopenia: a case of missing, wandering or ineffective T cells

Idiopathic CD4 lymphocytopenia (ICL) is a presumed heterogenous syndrome with key element low CD4 T-cell counts (below 300/mm³) without evidence of HIV infection or other known immunodeficiency. The etiology, pathogenesis, and management of ICL remain poorly understood and inadequately defined. The clinical presentation can range from serious opportunistic infections to incidentally diagnosed asymptomatic individuals. Cryptococcal and non-tuberculous mycobacterial infections and progressive multifocal leukoencephalopathy are the most significant presenting infections, although the spectrum of opportunistic diseases can be similar to that in patients with lymphopenia and HIV infection. Malignancy is common and related to opportunistic pathogens with an oncogenic potential. Autoimmune diseases are also seen in ICL with an increased incidence. The etiology of ICL is unknown. Mechanisms implicated in CD4 reduction may include decreased production, increased destruction, and tissue sequestration. New distinct genetic defects have been identified in certain patients with ICL, supporting the hypothesis of the lack of a common etiology in this syndrome. The management of ICL is focused on the treatment of opportunistic infections, appropriate prophylactic antibiotics, and close monitoring. In selected patients with life-threatening infections or profound immunodeficiency, strategies to increase T-cell counts or enhance immune function could be considered and have included interleukin-2, interferon-gamma, interleukin-7, and hematopoietic stem cell transplantation. The prognosis is influenced by the accompanying opportunistic infections and may be affected by publication bias of severe cases with unfavorable outcomes. As newer laboratory investigation techniques are being developed and targeted experimental treatments become available, our comprehension and prognosis of this rare syndrome could be significantly improved.

[Lymphocytopenia: aetiology and diagnosis, when to think about idiopathic CD4(+) lymphocytopenia?]

Une lymphopénie est définie par un nombre de lymphocytes circulants inférieur à 1500/mm³ chez l’adulte et 4500/mm³ chez l’enfant avant huit mois. La lymphopénie peut être globale ou sélective, affectant une population lymphocytaire particulière. Le diagnostic étiologique doit tenir compte de l’âge, du contexte, des manifestations clinicobiologiques associées et des thérapeutiques reçues. Les lymphopénies de l’adulte peuvent être liées schématiquement à : (1) une insuffisance de production (carence en zinc, corticothérapie, déficits immunitaires primitifs…), (2) un excès de catabolisme (radiothérapie, chimiothérapie, traitements immunosuppresseurs, infection par le VIH ou lupus systémique, etc.), (3) une modification de la répartition des lymphocytes (infections virales, choc septique, brûlures étendues, hypersplénisme, granulomatoses, etc.), (4) les étiologies multifactorielles ou non identifiées (insuffisance rénale chronique, certaines hémopathies lymphoïdes, tumeur solide, causes ethniques, etc.). Chez l’enfant, à ces étiologies s’ajoutent d’autres déficits immunitaires primitifs d’expression sévère (défaut des précurseurs thymiques, déficit cytokinique, défaut de synthèse des récepteurs des lymphocytes B et T et défaut de la transduction du signal ou des interactions cellulaires). La lymphopénie CD4⁺ idiopathique de l’adulte est un diagnostic d’élimination. Cette affection rare se définit par une lymphopénie T CD4⁺ inférieure ou égale à 300/mm³ ou inférieure ou égale à 20 % des lymphocytes totaux, persistante en l’absence de diagnostic alternatif. Elle peut être asymptomatique, s’associer à des infections à germes opportunistes, ou se compliquer de symptômes auto-immuns (en particulier cytopénies) ainsi que de néoplasies. Le traitement, calqué sur la prise en charge des patients infectés par le VIH, peut nécessiter le recours à une immunothérapie spécifique dont le bénéfice clinique reste à évaluer.

Cryptococcosis and idiopathic CD4 lymphocytopenia

We reviewed the cases of 11 patients with cryptococcosis and idiopathic CD4 lymphocytopenia (ICL) referred to our institution in the previous 12 years, as well as 42 similar cases reported in the literature, to assess the characteristics of the infection in this population. Cryptococcosis in 53 patients with ICL had features in common with cryptococcosis in previously normal patients. ICL patients had a slight male predominance (1.2:1) and a median age of presentation of 41 years (range, 4.5-85 yr). Initial cerebrospinal fluid findings showed glucose below 40 mg/dL in 60% of the patients, a median pleocytosis of 59 white blood cells/mm (range, 0-884), and protein of 156 mg/dL (range, 25-402 mg/dL). The median CD4 count at diagnosis of ICL and at the last available measurement was 82 (range, 7-292) and 132 (range, 13-892) cells/mm, respectively, for an average follow-up of 32 months in 46 patients. Unlike previously normal patients with cryptococcosis, those with ICL had an excess incidence of dermatomal zoster (7 episodes in 46 ICL cases). Pneumocystis pneumonia was rare (1 case), casting doubt on the need for prophylaxis in patients with ICL. A favorable outcome (cured or improved) may be more common in ICL patients than in previously normal patients with cryptococcal meningitis and no predisposing factors. Identification of ICL in patients who were apparently normal before the onset of cryptococcosis appears to be useful because it predicts a favorable outcome. Patients with cryptococcal infection and ICL have an increased likelihood of developing dermatomal zoster. The long-term follow-up of these patients offers some reassurance regarding favorable prognosis.

T-lymphocyte production, function, and death in children who recovered from opsoclonus-myoclonus syndrome

Reduced CD4+ lymphocytes have been recently found in peripheral blood of children with active opsoclonus-myoclonus syndrome. The authors identified 2 children who recovered from this syndrome, one of whom showed reduced CD4+ lymphocytes 2 years after the disease onset. Except for a decrease of "naive" CD45RA+ CD4+ population and a mild restriction of T-cell heterogeneity in this patient, probably related to the immune response to viral infections, no alterations of T-cell homeostasis and function were found in either child. Therefore, the decrease of CD4+ cells may persist after clinical recovery, but the causes of this abnormality cannot be ascribed to intrinsic T-cell defects.

Idiopathic CD4 lymphocytopenia

PURPOSE OF REVIEW

A severe decrease of CD4 T cells predisposes humans to opportunistic infections. In adults, HIV is certainly the most common cause of CD4 lymphocytopenia, but other causes, such as infections, autoimmune diseases, immunosuppressive therapy, lymphoma and idiopathic forms need to be considered. This review summarizes the current knowledge of the poorly understood syndrome of idiopathic CD4 lymphocytopenia.

RECENT FINDINGS

Little research has tried to systematically dissect this probably heterogeneic syndrome after its initial description in 1992. Numerous cases presenting with opportunistic infections have been reported. Disturbed differentiation of stem cell precursors may contribute to CD4 lymphocytopenia. Because infections and lymphoma may also cause CD4 lymphocytopenia, the distinction between cause and effect may evolve only during follow-up.

SUMMARY

The manifestation of opportunistic infections calls for the evaluation of the immune system for CD4 lymphocytopenia. The differential diagnosis of this condition in adults comprises primarily HIV infection and less often other diseases or drugs. Idiopathic CD4 lymphocytopenia is very rare. The clinical significance of low CD4 cell counts in HIV negative patients still awaits its systematic analysis. Prophylaxis of opportunistic infections is oriented at the recommendations of HIV-infected individuals and causal treatment remains experimental.

Reduced thymic output, increased spontaneous apoptosis and oligoclonal B cells in polyethylene glycol-adenosine deaminase-treated patients

Impairment of purine metabolism due to adenosine deaminase (ADA) deficiency is associated with a severe combined immunodeficiency (SCID). Polyethylene glycol-modified ADA (PEG-ADA) has provided noncurative, life-saving treatment for these patients, but full immune recovery is not achieved with this therapy. Since ADA-SCID is perhaps the most difficult form of SCID to handle clinically, understanding the benefits and limitations of PEG-ADA therapy may be relevant for treatment selection. To this purpose, we analyzed the rate of thymic output, T and B cell repertoires, number of T cell divisions, IFN-gamma and IL-4 production, and the extent of cell death in five ADA-SCID patients following a prolonged period of treatment with PEG-ADA. We found that thymic output was low in these patients. However, their T cell repertoire was heterogeneous, and their T lymphocytes produced cytokines upon activation and responded to mitogen stimulation, although with different kinetics. Furthermore, a high number of peripheral T lymphocytes were committed to apoptosis. Anomalies were also observed in the B cell compartment, with oligoclonal expansions of B cell clonotypes in two patients. Our data indicate that decreased thymic function, B cell oligoclonality, and increased spontaneous apoptosis may be the mechanisms by which the immunodeficiency of ADA-SCID patients persists in spite of treatment with PEG-ADA.

Post-natal ontogenesis of the T-cell receptor CD4 and CD8 Vbeta repertoire and immune function in children with DiGeorge syndrome

DiGeorge syndrome (DGS) is a congenital disorder characterized by typical facial features, hypoparatyroidism, conotruncal cardiac defects and thymic hypoplasia. Although there are some reports addressing lymphocytes counts and function in DGS children over time, few data have been reported on the T-cell receptor V beta (TCRBV) repertoire in relation to disease progression. The aim of this study was to evaluate the degree and nature of immunodeficiency and to investigate a possible correlation to clinical findings. We used third complementary region (CDR3) size spectratyping as a tool for monitoring T-cell repertoire diversity in 7 DGS's children. The rate of thymic output, the phenotype and function of peripheral T-cells and the humoral immunity were also investigated. At baseline a profound alteration of the TCR repertoire was noted, mainly in the CD8+ T-cells, in DGS patients when compared to a control group. Furthermore, analysis of thymic output showed a significant decrease in TCR rearrangement excision circles (TRECs) levels in the patient group. Immunoglobulin abnormalities were also detected. The observed TCR repertoire alterations, although not statistically significant, may suggest an increased susceptibility to infections. A parallel increase in the TCR repertoire diversity and clinical improvement occurred during the follow-up. Our results confirm that the extent of immunodeficiency is highly variable and could improve through childhood, and indicate that TCR repertoire may be a useful marker to clinically monitor thymic function in this primary immunodeficiency.

Profound loss of T-cell receptor repertoire complexity in cutaneous T-cell lymphoma

Cutaneous T-cell lymphoma (CTCL) is a malignancy of skin-homing T cells. A major feature of CTCL is profound immunosuppression, such that patients with advanced mycosis fungoides or Sézary syndrome have been compared with patients with advanced HIV disease and are susceptible to opportunistic infection. The etiology of this immunosuppression is unclear. We analyzed peripheral blood T cells of patients with CTCL with stage I to IV disease, using a sensitive beta-variable complementarity-determining region 3 spectratyping approach. Our data revealed a profound disruption of the complexity of the T-cell repertoire, which was universally observed in patients with advanced disease (stages III and IV), and present in up to 50% of patients with early-stage disease (stages I and II). In most patients, multiple monoclonal and oligoclonal complementarity-determining region 3 (CDR3) spectratype patterns in many different beta-variable families were seen. Equally striking was a reduction of normal T cells (as judged by absolute CD4 counts) across multiple beta-variable families. In general, CTCL spectratypes were reminiscent of advanced HIV spectratypes published elsewhere. Taken together, these data are most consistent with a global assault on the T-cell repertoire in patients with CTCL, a process that can be observed even in early-stage disease.

Restriction in T-cell receptor repertoire in a patient affected by trichothiodystrophy and CD4+ lymphopenia

Molecular analysis of T-cell receptor (TCR) repertoire, by measuring the CDR3 heterogeneity length of beta-variable regions (spectratyping), is useful for acquiring novel information on the status of immune system in primary immunodeficiency. Here, we evaluate TCR repertoire in a child with trichothiodystrophy (TTD) and combined immunodeficiency (CID). Spectratyping revealed marked alterations of TCR repertoire distribution: 21 and 10 out of 27 TCR Vbeta (TCRBV) families and subfamilies were skewed in CD8+ and CD4+ subsets, respectively. These findings revealed, for the first time in a TTD patient with CID, a marked reduction in the TCR repertoire complexity, which may reflect alterations in the mechanisms regulating the generation and homeostasis of T cells.

Human immunedeficiency virus type 1 (HIV-1) disease progression may be due to defects in the expression of the TCR/CD3 complex as well as to a T CD4+ cell deficit

The loss of T CD4+ cells leading to impairment of the immune system is the major cause of disease progression during HIV infection. More recently, the use of highly active anti-retroviral therapy (HAART) has raised important questions regarding the immune system restoration. Idiopathic CD4+ T lymphocytopenia syndrome (ICL) is similar to AIDS, except for the presence of HIV. Despite this similarity, ICL patients have a longer survival time than AIDS cases without HAART. The impairment of TCR/CD3-directed CD4+ T cell immune responses may be responsible for HIV disease progression. We think that the reduction of opportunistic infections which lead to death after HAART, is due to the ability of these memory clones to restore enough clones of the TCR/CD3 complex with fair capacity and diversity to confront frequent pathogens.