Apoptotic depletion of CD4+ T cells in idiopathic CD4+ T lymphocytopenia

Reappraisal of Idiopathic CD4 Lymphocytopenia at 30 Years

BACKGROUND

Idiopathic CD4 lymphocytopenia (ICL) is a clinical syndrome that is defined by CD4 lymphopenia of less than 300 cells per cubic millimeter in the absence of any primary or acquired cause of immunodeficiency. Some 30 years after its original identification, ICL has remained a disease of obscure cause, with limited evidence with respect to its prognosis or management, despite diagnostic and therapeutic innovations.

METHODS

We evaluated the clinical, genetic, immunologic, and prognostic characteristics of 108 patients who were enrolled during an 11-year period. We performed whole-exome and targeted gene sequencing to identify genetic causes of lymphopenia. We also performed longitudinal linear mixed-model analyses of T-cell count trajectories and evaluated predictors of clinical events, the response to immunization against coronavirus disease 2019 (Covid-19), and mortality.

RESULTS

After the exclusion of patients with genetic and acquired causes of CD4 lymphopenia, the study population included 91 patients with ICL during 374 person-years of follow-up. The median CD4+ T-cell count among the patients was 80 cells per cubic millimeter. The most prevalent opportunistic infections were diseases related to human papillomavirus (in 29%), cryptococcosis (in 24%), molluscum contagiosum (in 9%), and nontuberculous mycobacterial diseases (in 5%). A reduced CD4 count (<100 cells per cubic millimeter), as compared with a CD4 count of 101 to 300 cells, was associated with a higher risk of opportunistic infection (odds ratio, 5.3; 95% confidence interval [CI], 2.8 to 10.7) and invasive cancer (odds ratio, 2.1; 95% CI, 1.1 to 4.3) and a lower risk of autoimmunity (odds ratio, 0.5; 95% CI, 0.2 to 0.9). The risk of death was similar to that in the age- and sex-adjusted general population, but the prevalence of cancer was higher.

CONCLUSIONS

Among the study patients, ICL continued to be associated with increased susceptibility to viral, encapsulated fungal, and mycobacterial diseases, as well as with a reduced response to novel antigens and an increased risk of cancer. (Funded by the National Institute of Allergy and Infectious Diseases and the National Cancer Institute; ClinicalTrials.gov number, NCT00867269.).

Autoantibodies in immunodeficiency syndromes: The Janus faces of immune dysregulation

Immunodeficiency syndromes represent a diverse group of inherited and acquired disorders, characterized by a spectrum of clinical manifestations, including recurrent infections, autoimmunity, lymphoproliferation and malignancy. Autoantibodies against various self-antigens reflect the immune dysregulation underlying these disorders, and could contribute to certain clinical findings, such as susceptibility to opportunistic infections, cytopenia of different hematopoietic lineages, and organ-specific autoimmune diseases. The mechanism of autoantibody production in the context of immunodeficiency remains largely unknown but is likely shaped by both intrinsic genetic aberrations and extrinsic exposures to possible infectious agents. These autoantibodies if harbor neutralizing activities and reach certain levels in the circulation, could disrupt the biological functions of their targets, resulting in specific clinical manifestations. Herein, we reviewed the prevalence of autoantibodies against cytokines, hematopoietic cells and organ-specific antigens in immunodeficiency syndromes and examined their associations with certain clinical findings. Moreover, the potential mechanism of autoantibody production was also discussed. These may shed light on the development of mechanism-based therapies to reset the dysregulated immune system in immunodeficient patients.

Prevalence and pathogenicity of autoantibodies in patients with idiopathic CD4 lymphopenia

BACKGROUNDIdiopathic CD4 lymphopenia (ICL) is defined by persistently low CD4+ cell counts (<300 cells/μL) in the absence of a causal infection or immune deficiency and can manifest with opportunistic infections. Approximately 30% of ICL patients develop autoimmune disease. The prevalence and breadth of their autoantibodies, however, and their potential contribution to pathogenesis of ICL remain unclear.METHODSWe hybridized 34 and 51 ICL patients' sera to a 9,000-human-proteome array and to a 128-known-autoantigen array, respectively. Using a flow-based method, we characterized the presence of anti-lymphocyte Abs in the whole cohort of 72 patients, as well as the Ab functional capability of inducing Ab-dependent cell-mediated cytotoxicity (ADCC), complement deposition, and complement-dependent cytotoxicity (CDC). We tested ex vivo the activation of the classical complement pathway on ICL CD4+ T cells.RESULTSAll ICL patients had a multitude of autoantibodies mostly directed against private (not shared) targets and unrelated quantitatively or qualitatively to the patients' autoimmune disease status. The targets included lymphocyte intracellular and membrane antigens, confirmed by the detection by flow of IgM and IgG (mostly IgG1 and IgG4) anti-CD4+ cell Abs in 50% of the patients, with half of these cases triggering lysis of CD4+ T cells. We also detected in vivo classical complement activation on CD4+ T cells in 14% of the whole cohort.CONCLUSIONOur data demonstrate that a high prevalence of autoantibodies in ICL, some of which are specific for CD4+ T cells, may contribute to pathogenesis, and may represent a potentially novel therapeutic target.TRIAL REGISTRATIONClinicalTrials.gov NCT00867269.FUNDINGNIAID and National Institute of Arthritis and Musculoskeletal and Skin Diseases of the NIH.

Idiopathic CD4 T Cell Lymphocytopenia: A Case of Overexpression of PD-1/PDL-1 and CTLA-4

Idiopathic CD4 T cell lymphocytopenia (ICL) is a rare entity characterized by CD4 T cell count of <300 cells/mm³ along with opportunistic infection for which T cell marker expression remains to be fully explored. We report an ICL case for which T lymphocyte phenotype and its costimulatory molecules expression was analyzed both ex vivo and after overnight stimulation through CD3/CD28. The ICL patient was compared to five healthy controls. We observed higher expression of inhibitory molecules PD-1/PDL-1 and CTLA-4 on CD4 T cells and increased regulatory T cells in ICL, along with high activation and low proliferation of CD4 T cells. The alteration in the expression of both the costimulatory pathway and the apoptotic pathway might participate to down-regulate both CD4 T cell functions and numbers observed in 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 CD4-positive lymphocytopenia-associated progressive multifocal leukoencephalopathy confirmed by brain biopsy following negative results of repeated CSF-JC-virus tests: a case report]

A 75-year-old man presented with dysarthria and left facial paralysis. Brain diffusion-weighted MRI revealed a high-signal intensity in the right precentral gyrus, and he was hospitalized under the diagnosis of cerebral infarction. His symptoms worsened and brain MRI findings were consistent with progressive multifocal leukoencephalopathy (PML). Cerebrospinal fluid (CSF) JC virus (JCV) was undetectable in the DNA polymerase chain reaction (PCR) test four times, but brain biopsy revealed typical PML histopathology. He had no human immunodeficiency virus infection and history of immunosuppressive treatment, but he was found to have CD4+ lymphocytopenia. He was treated with mefloquine and mirtazapine, and died 29 months after symptoms onset. In cases whose repeated DNA PCR results are negative for CSF JCV, brain biopsy may be useful for the diagnosis of PML.

DUSP4-mediated accelerated T-cell senescence in idiopathic CD4 lymphopenia

Idiopathic CD4 lymphopenia (ICL) is a rare heterogeneous immunological syndrome of unclear etiology. ICL predisposes patients to severe opportunistic infections and frequently leads to poor vaccination effectiveness. Chronic immune activation, expansion of memory T cells, and impaired T-cell receptor (TCR) signaling have been reported in ICL, but the mechanistic and causative links remain unclear. We show that late-differentiated T cells in 20 patients with ICL displayed defective TCR responses and aging markers similar to those found in T cells from elderly subjects. Intrinsic T-cell defects were caused by increased expression of dual-specific phosphatase 4 (DUSP4). Normalization of DUSP4 expression using a specific siRNA improved CD4(+) T-cell activity in ICL, as this restored TCR-induced extracellular signal-regulated kinase activation and increased the expression of the costimulatory molecules CD27 and CD40L. Conversely, repeated TCR stimulation led to defective signaling and DUSP4 overexpression in control CD4(+) T cells. This was associated with gradual acquisition of a memory phenotype and was curtailed by DUSP4 silencing. These findings identify a premature T-cell senescence in ICL that might be caused by chronic T-cell activation and a consequential DUSP4-dependent dampening of TCR signaling.

Idiopathic CD4 lymphocytopenia: clinical and immunologic characteristics and follow-up of 40 patients

Idiopathic CD4 T lymphocytopenia (ICL) is a rare and severe condition with limited available data. We conducted a French multicenter study to analyze the clinical and immunologic characteristics of a cohort of patients with ICL according to the Centers for Disease Control criteria.We recruited 40 patients (24 female) of mean age 44.2 ± 12.2 (19-70) years. Patients underwent T-lymphocyte phenotyping and lymphoproliferation assay at diagnosis, and experiments related to thymic function and interferon (IFN)-γ release by natural killer (NK) cell were performed. Mean follow-up was 6.9 ± 6.7 (0.14-24.3) years. Infectious, autoimmune, and neoplastic events were recorded, as were outcomes of interleukin 2 therapy.In all, 25 patients had opportunistic infections (12 with human papillomavirus infection), 14 had autoimmune symptoms, 5 had malignancies, and 8 had mild or no symptoms. At the time of diagnosis, the mean cell counts were as follows: mean CD4 cell count: 127/mm (range, 4-294); mean CD8: 236/mm (range, 1-1293); mean CD19: 113/mm (range, 3-547); and mean NK cell count: 122/mm (range, 5-416). Most patients had deficiency in CD8, CD19, and/or NK cells. Cytotoxic function of NK cells was normal, and patients with infections had a significantly lower NK cell count than those without (p = 0.01). Patients with autoimmune manifestations had increased CD8 T-cell count. Proliferation of thymic precursors, as assessed by T-cell rearrangement excision circles, was increased. Six patients died (15%). CD4 T-cell count <150/mm and NK cell count <100/mm were predictors of death.In conclusion, ICL is a heterogeneous disorder often associated with deficiencies in CD8, CD19, and/or NK cells. Long-term prognosis may be related to initial CD4 and NK cell deficiency.

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.

Primary immunodeficiencies: a rapidly evolving story

The characterization of primary immunodeficiencies (PIDs) in human subjects is crucial for a better understanding of the biology of the immune response. New achievements in this field have been possible in light of collaborative studies; attention paid to new phenotypes, infectious and otherwise; improved immunologic techniques; and use of exome sequencing technology. The International Union of Immunological Societies Expert Committee on PIDs recently reported on the updated classification of PIDs. However, new PIDs are being discovered at an ever-increasing rate. A series of 19 novel primary defects of immunity that have been discovered after release of the International Union of Immunological Societies report are discussed here. These new findings highlight the molecular pathways that are associated with clinical phenotypes and suggest potential therapies for affected patients.

Consequences of a mutation in the UNC119 gene for T cell function in idiopathic CD4 lymphopenia

The activation of a T cell through T cell receptor (TCR) is fundamental to adaptive immune responses. The lymphocyte specific kinase (LCK) plays a central role in the initiation of signaling from the TCR. TCR activates LCK through the adaptor protein uncoordinated 119 (UNC119). A mutation of human UNC119 impairs LCK activation and is associated with inadequate signaling, diminished T cell responses to TCR stimulation, CD4 lymphopenia, and infections of viral, bacterial, and fungal origin. The above clinical and immunological findings meet the criteria of the idiopathic CD4 lymphopenia (ICL). The discovery of the UNC119 defect provides a molecular mechanism for a subset of patients with this previously unexplained disease. Here we review our recent findings on the UNC119 mutation in ICL.

Altered responses to homeostatic cytokines in patients with idiopathic CD4 lymphocytopenia

Idiopathic CD4 lymphocytopenia (ICL) is a rare immune deficiency characterized by a protracted CD4(+) T cell loss of unknown etiology and by the occurrence of opportunistic infections similar to those seen in AIDS. We investigated whether a defect in responses to cytokines that control CD4(+) T cell homeostasis could play a role in ICL. Immunophenotype and signaling responses to interleukin-7 (IL-7), IL-2, and thymic stromal lymphopoietin (TSLP) were analyzed by flow cytometry in CD4(+) T cells from 15 ICL patients and 15 healthy blood donors. The induction of phospho-STAT5 after IL-7 stimulation was decreased in memory CD4(+) T cells of some ICL patients, which correlated with a decreased expression of the IL-7Rα receptor chain (R = 0.74, p<0.005) and with lower CD4(+) T cell counts (R = 0.69, p<0.005). IL-2 responses were also impaired, both in the Treg and conventional memory subsets. Decreased IL-2 responses correlated with decreased IL-7 responses (R = 0.75, p<0.005), pointing to combined defects that may significantly perturb CD4(+) T cell homeostasis in a subset of ICL patients. Unexpectedly, responses to the IL-7-related cytokine TSLP were increased in ICL patients, while they remained barely detectable in healthy controls. TSLP responses correlated inversely with IL-7 responses (R = -0.41; p<0.05), suggesting a cross-regulation between the two cytokine systems. In conclusion, IL-7 and IL-2 signaling are impaired in ICL, which may account for the loss of CD4(+) T cell homeostasis. Increased TSLP responses point to a compensatory homeostatic mechanism that may mitigate defects in γc cytokine responses.

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.

Decreased interleukin 7 responsiveness of T lymphocytes in patients with idiopathic CD4 lymphopenia

BACKGROUND

Elevated serum interleukin 7 (IL-7) levels are observed in lymphopenic conditions, including idiopathic CD4 lymphopenia (ICL), which is characterized by CD4 lymphopenia in the absence of human immunodeficiency virus infection or other known immunodeficiency.

METHODS

To test whether defective IL-7 signaling could be an etiologic or contributing factor in ICL, peripheral blood mononuclear cells from patients with ICL (median CD4 T-cell count, 160 cells/μL) and healthy controls (median CD4 T-cell count, 582 cells/μL) were evaluated for expression of IL-7Rα chain (CD127) and intracellular phosphorylated STAT-5 (a marker of γc cytokine signaling) after cytokine stimulation. Gene expression was analyzed by real-time polymerase chain reaction following IL-7 stimulation.

RESULTS

The percentage of CD4+CD127+ T cells was lower in patients with ICL, compared with controls (P < .001). Lower levels of STAT-5 phosphorylation after IL-7 stimulation were observed in both CD4 and CD8 T cells from patients with ICL, compared with controls (P < .001 and P = .017, respectively), that inversely correlated in CD4 T cells with serum IL-7 levels (r = -0.734, P = .013). Destabilization of p27(kip1), a critical step for IL-7-induced T-cell cycling, was decreased in patients with ICL, compared with controls (P = .004), after IL-7 stimulation.

CONCLUSIONS

These data suggest that diminished responsiveness to IL-7 in CD4 and CD8 T cells during ICL may be contributing to the dysregulation of T-cell homeostasis.

Successful treatment of sepsis caused by Staphylococcus lugdunensis in an adult with 22q11.2 deletion syndrome

A 27-year-old woman visited our hospital because of high fever. She had been diagnosed as 22q11.2 deletion syndrome (22q11.2DS) due to her cardiac history (tetralogy of Fallot), thymic hypoplasia and 22q11.2 deletion. She had a normal CD4/CD8 ratio, a slightly decreased lymphocyte count and normal serum immunoglobulin levels. Blood cultures were positive for Staphylococcus lugdunensis (S. lugdunensis). Infection route of S. lugdunensis in this case was unclear. The patient was successfully treated with several intravenous antibiotics. Infection should be considered when managing patients with 22q.11.2DS. regardless of whether their immune system is impaired.

A mutation in the human Uncoordinated 119 gene impairs TCR signaling and is associated with CD4 lymphopenia

Idiopathic CD4 lymphopenia (ICL) is an immunodeficiency disorder of unclear etiology. Here we describe a heterozygous dominant-negative missense mutation (codon 22 GGC→GTC; V22G) of the signaling adaptor protein Uncoordinated 119 (Unc119) in an ICL patient. The patient is a 32-year-old female with < 300 CD4 T cells/μL and with a history of recurrent sinusitis/otitis media, frequent episodes of shingles, a widespread fungal nail infection, fungal dermatitis, oral herpetic lesions, and bronchiolitis obliterans organizing pneumonia after 2 episodes of bacterial pneumonia. The patient's cells have reduced response to TCR stimulation, with impairment in both localization and enzymatic activation of the lymphocyte-specific kinase (Lck) resulting in decreased cell proliferation. Transduction of the mutant Unc119 but not wild-type Unc119 into normal T cells reproduces the signaling and proliferation defects. The mutation disrupts the Unc119-Lck interaction which is normally needed for stimulation of the Lck catalytic activity by TCR. The mutant protein also causes mislocalization of Lck to Rab11(+) perinuclear endosomes. The mutation is not present in 2 other patients with ICL, patients with secondary CD4 lymphopenia or 60 healthy subjects. The V22G mutation of Unc119 represents a novel genetic defect in ICL.

Orbital lymphoma in the setting of idiopathic CD4+ lymphocytopenia (HIV-negative AIDS)

A 43-year-old Asian man with idiopathic CD4+ lymphocytopenia (human immunodeficiency virus [HIV]-negative acquired immunodeficiency syndrome [AIDS]) noted blurred vision OD. Visual acuity was 20/30 OD and 20/15 OS. The right eye showed features of axial proptosis (2 mm), blepharoptosis, upgaze restriction, conjunctival chemosis, color desaturation, and choroidal folds. The OS was unremarkable. There was no lymphadenopathy. Orbital MRI showed a well-circumscribed mass indenting the globe. Excision revealed diffuse large-B-cell lymphoma. Systemic evaluation was negative and adjuvant external beam radiotherapy to the right orbit was performed. Idiopathic CD4+ lymphocytopenia is a rare hematologic condition characterized by depletion of CD4+ T cells in HIV-negative patients. This condition closely resembles AIDS but HIV serology is negative. Similar to AIDS, patients are at risk for opportunistic infections and neoplasia, including systemic lymphoma. This is the first case, to the authors' knowledge, of orbital lymphoma with idiopathic CD4+ lymphocytopenia.

[Dysfunctions of the CXCL12 (SDF-1)/CXCR4 signaling axis in the WHIM syndrome and the idiopathic CD4(+) T-cell lymphocytopenia]

Chemokines are small cytokine-like secreted proteins that govern migration of leukocytes to their specific niches in lymphoid organs and to inflammatory sites. They mediate their functions by binding to and activating chemokine receptors, which belong to the heptahelical G protein-coupled receptor family. The CXC chemokine Stromal cell Derived Factor-1 (SDF-1/CXCL12) is the sole natural ligand for the broadly expressed CXCR4 receptor and acts as a chemoattractant for many leukocyte subsets. The CXCL12/CXCR4 axis exerts critical activities in homeostatic processes such as organogenesis, hematopoiesis and leukocyte trafficking. Dysregulations of CXCR4 signaling and/or expression are associated with several infectious, inflammatory, autoimmune and malignant conditions. In light of recent data, we review here CXCR4 dysfunctions unveiled in two rare human immunodeficiency disorders, one characterized by a gain of CXCR4 function, the WHIM syndrome, and the other by a loss of CXCR4 function, the idiopathic CD4(+) T-cell lymphocytopenia.

Idiopathic CD4+ T-cell lymphocytopenia is associated with impaired membrane expression of the chemokine receptor CXCR4

Idiopathic CD4(+) T-cell lymphocytopenia (ICL) is a rare acquired T-cell immunodeficiency of unknown pathogenic basis. Six adults with ICL who developed opportunistic infections were investigated using extensive immunophenotyping analysis and functional evaluation of the chemokine receptor CXCR4. For all 6 patients studied, a profound defect in CXCR4 expression was detected at the surface of CD4(+) T lymphocytes, in association with an abnormal intracellular accumulation of CXCR4 and of its natural ligand, the chemokine CXCL12. For all patients studied, CD4(+) T-cell chemotactic response toward CXCL12 was decreased, whereas sensitivity to CXCL8 was preserved. CXCR4 recovery after ligand-induced endocytosis was impaired in ICL CD4(+) T cells. Upon in vitro addition of interleukin-2 (IL-2), membrane expression of CXCR4 returned to normal levels in 5 of 6 patients, whereas intracellular accumulation of CXCR4 and CXCL12 disappeared. Upon therapeutic administration of IL-2, CD4(+) T-cell count and membrane CXCR4 expression and function improved over time in 3 of 4 patients treated. Therefore, our data indicate that ICL is associated with defective surface expression of CXCR4, which may be reversed by IL-2.

Disseminated giant molluscum contagiosum in a patient with idiopathic CD4+ lymphocytopenia. Successful eradication with systemic interferon

Idiopathic CD4+ lymphocytopenia is a rare disease without HIV infection or any other underlying immunodeficiency. Patients with this condition are predisposed to various opportunistic infections. We describe a 31-year-old woman with giant molluscum contagiosum disseminated over nearly the whole body. Immunologic analysis disclosed very low numbers of CD4+ lymphocytes (<11/microl, normal range: 240-3,100), an abnormal proliferative response of the patient's lymphocytes to artificial mitogens and specific antigens, and an anergic delayed-type hypersensitivity skin response. HIV serology was repetitively negative. The diagnosis of idiopathic CD4+ lymphocytopenia was established. Systemic treatment with pegylated interferon-alpha2b (50 microg/week) for 16 months resulted in complete eradication of her disseminated giant molluscum contagiosum. In this report we will further describe the nature of idiopathic CD4+ lymphocytopenia and emphasize its relevance to clinical dermatology.

Idiopathic CD4+ lymphocytopenia: natural history and prognostic factors

Idiopathic CD4(+) lymphocytopenia (ICL) is a rare non-HIV-related syndrome with unclear natural history and prognosis. This prospective natural history cohort study describes the clinical course, CD4 T lymphocyte kinetics, outcome, and prognostic factors of ICL. Thirty-nine patients (17 men, 22 women) 25 to 85 years old with ICL were evaluated between 1992 and 2006, and 36 were followed for a median of 49.5 months. Cryptococcal and nontuberculous mycobacterial infections were the major presenting opportunistic infections. Seven patients presented with no infection. In 32, CD4 T-cell counts remained less than 300/mm(3) throughout the study period and in 7 normalized after an average of 31 months. Overall, 15 (41.6%) developed an opportunistic infection in follow-up, 5 (13.8%) of which were "AIDS-defining clinical conditions," and 4 (11.1%) developed autoimmune diseases. Seven patients died, 4 from ICL-related opportunistic infections, within 42 months after diagnosis. Immunologic analyses revealed increased activation and turnover in CD4 but not CD8 T lymphocytes. CD8 T lymphocytopenia (< 180/mm(3)) and the degree of CD4 T cell activation (measured by HLA-DR expression) at presentation were associated with adverse outcome (opportunistic infection-related death; P = .003 and .02, respectively).

Detection of CD4(+) T-cell antibodies in a patient with idiopathic CD4 T lymphocytopenia and cryptococcal meningitis

Idiopathic CD4(+) T lymphocytopenia (ICL) is defined as a CD4(+) T-cell count <0.3 x 10(9)/l or <20% of the total T-cell count on two occasions in the absence of any immunodeficiency disorder or therapy associated with reduced CD4(+) T-cell count. Although several mechanisms of ICL have been reported, the pathophysiology is still largely unknown. This case report describes a patient who presented with cryptococcal meningitis and was subsequently discovered to meet the criteria for ICL. Flow cytometric analysis of the patient's peripheral blood mononuclear cells revealed antibodies coating a much larger proportion of his CD4(+) T cells (33.61%) than the CD4(+) T cells of normal donors (3.94 +/- 1.77%). The reasons behind the development of these autoantibodies are explored.

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.

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.

Apoptosis of T cells in peripheral blood and cerebrospinal fluid is associated with disease activity of multiple sclerosis

Apoptotic elimination of pathogenic T cells is considered to be one of regulatory mechanisms in multiple sclerosis (MS). To explore the potential relationship between Fas-mediated apoptosis and the disease course of MS, we examined apoptosis, defined by annexin V (AV) binding, and Fas (CD95) expression in CD4+ and in CD8+ T cells in MS patients by using five-color flow cytometry. The percentage of AV+CD4+CD3+ cells and CD95+AV+CD4+CD3+ cells in peripheral blood and cerebrospinal fluid (CSF) were significantly decreased in active MS patients compared with inactive MS patients. A significantly lower proportion of CD95+AV+CD8+CD3+ cells in CSF was observed in active MS patients compared with inactive MS patients, but not in peripheral blood. These results indicate that the resistance of T cells to Fas-mediated apoptosis is involved in exacerbation of MS and/or that Fas-mediated apoptosis of T cells is associated with remission of MS.

Idiopathic CD4+ lymphocytopenia may be due to decreased bone marrow clonogenic capability

BACKGROUND

Idiopathic CD4+ lymphocytopenia is defined by a stable decrease of CD4+ T cells in the absence of any known cause of immune deficiency. The mechanisms responsible for the immunological impairment are still unknown, but a regenerative failure of hematopoietic stem/progenitor cells has been hypothesized.

METHODS

We evaluated in the bone marrow (BM) of 5 patients with idiopathic CD4+ lymphocytopenia the phenotype of BM progenitor cells, their differentiation capacity with colony-forming cells and long-term culture-initiating cell assays, in parallel with the spontaneous IL-7 production in the patient sera.

RESULTS

Compared with controls, a regenerative failure of hematopoietic stem cells has been observed, both in 'committed' and in 'uncommitted' progenitor cells, despite high IL-7 serum levels. The percentage of phenotypically primitive CD34+CD38-DR+ cells (this includes the lymphoid precursor cells) was decreased, suggesting an involvement of the more primitive BM compartment in the de novo T cell generation.

CONCLUSIONS

Despite the low number of patients, due to the low incidence of the disease, the decrease of primitive precursors sustains the possibility that diminished stem cell precursors might contribute to the development of CD4+ T cell depletion.

A case of pulmonary cryptococcosis with non-small cell lung cancer in idiopathic CD4+ T-lymphocytopenia

Cryptococcus neoformans commonly causes opportunistic infections in immunocompromised patients, especially in patients with AIDS. CD4+ T-lymphocytopenia in AIDS indicates an increased risk of opportunistic infection and a decline in immunological function. Idiopathic CD4 T-lymphocytopenia (ICL) is characterized by depletions in the CD4+ T-cell subsets, without evidence of HIV infection. Immunodeficiency can exist in the absence of laboratory evidence of HIV infection, and T-cell subsets should be evaluated in patients who present with unusual opportunistic infections. We report a case of pulmonary cryptococcosis and lung cancer in a patient with persistently low CD4+ cell counts, without evidence of HIV infection.

Change in serum concentrations of interleukin-2 and interferon-gamma during treatment of tuberculosis

We aimed to investigate changes in serum concentrations of the cytokines interleukin (IL)-2 and interferon (IFN)-gamma during the clinical course of active tuberculosis, to establish the presence of cellular immunity before and after treatment. Blood samples were taken from 18 patients with active tuberculosis before and 2 months after therapy; IL-2 and IFN-gamma concentrations were evaluated. The mean serum IL-2 concentration before therapy was 164.5 pg/ml (range 12-980 pg/ml) and the concentration 2 months after therapy was 92.11 pg/ml (range 1-490 pg/ml). The mean serum IFN-gamma concentrations were 10.83 pg/ml (range 1-22.2 pg/ml) and 4.64 pg/ml (range 1-28.5 pg/ml), respectively. The decrease in concentrations of both cytokines after therapy was statistically significant. Further studies investigating the benefits of adding cytokines to drug treatment for tuberculosis are needed.

Pleural cryptococcosis with idiopathic CD4 positive T-lymphocytopenia

A 19-year-old man was admitted to our hospital because of chest pain. He was diagnosed as having pleural cryptococcosis by pleural biopsy. His CD4 positive T-lymphocyte count was low (< 300 microl) and there was no evidence of human immunodeficiency virus infection. He was successfully treated with fluconazole. However, his CD4 positive lymphocyte counts remained low after the recovery and he was diagnosed as idiopathic CD4 positive T-lymphocytopenia. Pleural cryptococcosis is rare and its predisposing condition is still controversial. To our knowledge, this is the first case of pleural cryptococcosis associated with idiopathic CD4 positive T lymphocytopenia.

Selective deficiency of naïve CD4+ T-lymphocytes in a child with congenital lymphoedema

We describe the first known case of congenital lymphoedema associated with selective deficit of naïve CD4+ T-lymphocytes. A high proportion of naïve CD4+ T-lymphocytes was found in the ascitic fluid, supporting the hypothesis of extra-vascular sequestration of these cells into lymphoedematous tissue.

Roxithromycin promotes lymphocyte apoptosis in Dermatophagoides-sensitive asthma patients

A new macrolide, roxithromycin, may be an effective treatment for asthma. Lymphocyte apoptosis is impaired in patients with asthma, while spontaneous apoptosis increases during remission, and such changes may be involved in the onset and remission of mite-sensitive asthma. Lymphocyte apoptosis was evaluated by incubating cells from patients with asthma in the presence of roxithromycin. Low concentrations of roxithromycin (1-500 ng/ml) augmented the early, but not late, phase of apoptosis in Dermatophagoides farinae-stimulated peripheral blood mononuclear (PBM) cells, while high concentrations of roxithromycin (1 microg/ml; 6 microg/ml is the maximum serum level) augmented both the early and late phases of apoptosis. In both unstimulated and phytohemagglutinin-stimulated cells, roxithromycin did not significantly affect the induction of apoptosis. In cells from normal subjects, roxithromycin did not affect the induction of apoptosis. Other antibiotics, including cefazolin and ampicillin, did not cause significant induction of apoptosis. Fas ligand, but not Fas receptor, expression on D. farinae-stimulated cells was up-regulated after stimulation with 1 microg/ml roxithromycin, while Bcl-2 expression on both unstimulated and D. farinae-stimulated cells showed a decrease after the same treatment. Roxithromycin can induce apoptosis of D. farinae-activated lymphocytes in patients with D. farinae-sensitive asthma. Induction of the Fas/Fas ligand system and reduced Bcl-2 expression were involved in the promotion of apoptosis by roxithromycin treatment.

Toxoplasmic myositis as a presenting manifestation of idiopathic CD4 lymphocytopenia

Toxoplasma gondii encysts in skeletal muscle. Although only rarely found at muscle biopsy, this parasite has previously been regarded as a possible cause of polymyositis. We report a case of biopsy-proven toxoplasmic myositis in a non-HIV-infected patient that led to recognition of idiopathic CD4 lymphocytopenia (ICL), a rare condition typically associated with opportunistic infections. Interestingly, the CD25(+) subset that corresponds to the CD4(+) regulatory T cells controlling autoimmune processes was lacking. Steroid and antiprotozoal therapy led to recovery.

Laboratory assessment of immune function in renal transplant patients

BACKGROUND

Advances in immunosuppression have made renal transplantation an effective therapy for end stage renal failure; with low rejection rates and long graft survival times. However, the major adverse consequences, infection and malignancy have not diminished. To predict this risk a score of immune competence has been developed from the simultaneous laboratory assessment of multiple parameters of immune function.

METHODS

The immune status of 152 transplant recipients (138 renal and 14 pancreas/renal) was assessed by measurement of lymphocyte subsets, mitogen-induced T-cell proliferative responses, neutrophil phagocytic capacity and reactive oxygen species (ROS) generation. A scoring system was devised based on the average number of these parameters below 10th percentile of normal.

RESULTS

The most common abnormality was B-cell lymphopenia (85%) followed by reduced neutrophil ROS production (63% of patients), NK cell lymphopenia (50%), lymphocyte mitogen response (49%) and CD4 number (23%). The abnormalities were unrelated to the duration of immunosuppression (up to 15 years), and variable combinations of cyclosporine A, azathioprine, prednisolone and mycophenolate mofetil (MMF) (except for a consistent reduction in lymphocyte mitogen response in MMF treated patients). Retrospective comparison of infective episodes showed a significantly greater index of infections in patients with the worst score compared with a normal score.

CONCLUSIONS

The data suggests that this quantification of immune function may allow assessment of the level of host immune defence reflecting the level of drug-induced immunosuppression and thus risks of immunosuppressive complications.

Immunodeficiency with recurrent panlymphocytopenia, impaired maturation of B lymphocytes, impaired interaction of T and B lymphocytes, and impaired integrity of epithelial tissue: a variant of idiopathic CD4+ T lymphocytopenia?

Idiopathic CD4+ T lymphocytopenia (ICL) has been defined as a cause of immunodeficiency with a variable clinical course and an unknown etiology. Here we describe a now 18-year-old boy with ICL, chronic mucocutaneous candidiasis (CMC), recurrent abscesses, and relapsing aphthous and ulcerous lesions. In addition to ICL the patient frequently showed a panlymphocytopenia. An increased percentage of gamma+delta+ T lymphocytes and IgD+ IgM+ B lymphocytes, and a decreased percentage of CD21+ B lymphocytes, were observed. In vitro assays showed normal T-cell responses to candidin and T-cell mitogens, but impaired B-cell responses to pokeweed mitogen (PWM). B-cell maturation after stimulation with Staphylococcus aureus Cowan I (SAC) and interleukin 2 (IL-2) was nearly normal. The clinical course of the patient improved substantially on administration of constant low-dose therapy with fluconazole.

Primary leptomeningeal lymphoma in a patient with concomitant CD4+ lymphocytopenia

BACKGROUND

Idiopathic CD4+ lymphocytopenia (ICL) is a rare disorder in which patients have mild and/or severe opportunistic infections or maybe without symptoms. The etiology is currently unknown. Diagnosis is made by excluding retroviral infections (human immunodeficiency virus-1 or -2, human T cell lymphotropic virus-1 or -2) or other known causes of immunosuppression.

OBJECTIVE

To provide a case report of a patient with possible ICL who presented with a rare form of primary non-Hodgkin lymphoma (NHL) of the central nervous system (CNS). Review of the literature has identified only five other patients with NHL and ICL; however, none of these had a CNS lymphoma.

RESULTS

We describe a patient with possible ICL, and address links between lymphopenia and lymphoproliferative disorders.

CONCLUSIONS

Although not uncommon for patients infected with human immunodeficiency virus to develop CNS NHL, this is the first case of a possible ICL patient with such a lymphoma. This case revisits an important relationship between lymphopenia and lymphoproliferative disorders.

Anti-platelet factor 4/heparin antibodies from patients with heparin-induced thrombocytopenia provoke direct activation of microvascular endothelial cells

Heparin-induced thrombocytopenia (HIT) is a serious complication that occurs in approximately 1-5% of patients treated with heparin and may be associated with severe thrombotic events. HIT is mediated by antibodies directed mostly to epitope(s) formed by complexes between heparin or other anionic mucopolysaccharides and platelet factor 4 (PF4). Anti-PF4/heparin IgG antibodies from six patients with HIT were affinity purified and assessed for interaction with human microvascular and macrovascular endothelial cells (EC). The antibodies directly activated primary cultures of human bone marrow microvascular EC (HBMEC) and SV40 immortalized HBMEC (TrHBMEC) only in the presence of PF4, but did not activate macrovascular human umbilical vein EC (HUVEC) under the same conditions. These antibodies were found to bind to TrHBMEC through the F(ab)(2) portion of the anti-PF4/heparin IgG. TrHBMEC activation was characterized by an augmented release of IL-6, von Willebrand factor, soluble thrombomodulin, and by an elevated expression of the adhesion molecules P-selectin, E-selectin and vascular cellular endothelial molecule-I to different degrees. Enhanced monocyte adhesion to PF4/heparin antibody-treated TrHBMEC (33-72% adhesion) was also observed. None of these effects occurred with unstimulated HUVEC. However, pre-treatment of HUVEC with tumor necrosis factor-alpha resulted in the same changes observed with microvascular EC exposed to the HIT antibodies. Our findings indicate that anti-PF4/heparin antibodies directly activate microvascular EC while interaction with macrovascular EC requires pre-activation. These results may explain some of the specific clinical manifestations in HIT.

Induction of cell death in human immunodeficiency virus-infected macrophages and resting memory CD4 T cells by TRAIL/Apo2l

Because the persistence of human immunodeficiency virus (HIV) in cellular reservoirs presents an obstacle to viral eradication, we evaluated whether tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) induces apoptosis in such reservoirs. Lymphocytes and monocyte-derived macrophages (MDM) from uninfected donors do not die following treatment with either leucine zipper human TRAIL (LZhuTRAIL) or agonistic anti-TRAIL receptor antibodies. By contrast, such treatment induces apoptosis of in vitro HIV-infected MDM as well as peripheral blood lymphocytes from HIV-infected patients, including CD4(+) CD45RO(+) HLA-DR(-) lymphocytes. In addition, LZhuTRAIL-treated cells produce less viral RNA and p24 antigen than untreated controls. Whereas untreated cultures produce large amounts of HIV RNA and p24 antigen, of seven treated CD4(+) CD45RO(+) HLA-DR(-) cell cultures, viral RNA production was undetectable in all, p24 antigen was undetectable in six, and proviral DNA was undetectable in four. These data demonstrate that TRAIL induces death of cells from HIV-infected patients, including cell types which harbor latent HIV reservoirs.

Red blood cells inhibit activation-induced cell death and oxidative stress in human peripheral blood T lymphocytes

Red blood cells (RBCs) are known to perform one prominent function: to carry and deliver oxygen to the tissues. Earlier studies, however, suggested a role for RBCs in potentiating T-cell proliferation in vitro. Here it is shown that the presence of RBCs in cultures of stimulated human peripheral blood lymphocytes strengthens T-cell proliferation and survival. Analysis of phosphatidylserine externalization and DNA fragmentation showed that RBCs inhibit T-cell apoptosis. This inhibition correlated with a reduction in CD71 but not CD95 expression. RBCs enhanced T-cell proliferation and survival upon activation with phytohemagglutinin and with OKT3 antibodies. Studies aimed at characterizing the cellular and molecular basis of the protection afforded to T cells by RBCs showed that (1) optimal protection required intact RBCs and red cell/T-cell contact but not monocytes; (2) RBCs markedly reduced the level of intracellular reactive oxygen species; and (3) RBCs inhibited the formation of protein-bound acrolein, a peroxidation adduct in biologic systems. Overall, these data indicate that human RBCs protect T cells from activation-induced cell death, at least in part by reducing the pro-oxidant state, and suggest a role for RBCs as conceivable modulators of T-cell homeostasis.

Apoptotic cell death in the pathogenesis of infectious diseases

Apoptosis is a physiological process critical for tissue homeostasis. It is essential for the regulation of immune responses. A series of molecules transduce apoptoic signals and induce the characteristic morphological appearances of apoptotic cells. Infectious diseases modulate apoptosis and this contributes to disease pathogenesis. Infection with HIV results in enhanced levels of CD4 T-lymphocyte apoptosis in both directly infected cells and in uninfected bystander cells. A variety of HIV proteins including gp120 contribute to this process. A number of different pathways induce HIV-associated CD4 T-lymphocyte apoptosis and apoptosis of uninfected bystander cells is particularly associated with increased susceptibility to Fas. Other viruses including hepatitis viruses and the human herpesviruses also modulate apoptosis. Bacterial infection induces apoptosis which is frequently mediated by the direct activation of caspases in the absence of death receptor ligation. Bacterial induction of apoptosis may either be due to bacterial factors such as the invasin IpaB of Shigella flexneri or be the result of host immune responses which control infection as demonstrated in infections due to Mycobacterium spp. Apoptosis may be modulated by therapeutic strategies, such as antiretroviral therapy, and an improved understanding of infection-associated apoptosis modulation will aid the design of novel therapeutic approaches to control infectious diseases.

Idiopathic CD4+ T cell lymphocytopenia evolving to monoclonal immunoglobulins and progressive renal damage responsive to IL-2 therapy

Idiopathic CD4+ T cell lymphocytopenia was unexpectedly detected in a 33-year-old, otherwise healthy young woman with no HIV or other viral infection, autoimmune, or neoplastic disease or increased susceptibility to infection. CD4+ T cell levels were 60-140/microl over a 3.5-year period. Following an uneventful pregnancy, the patient developed anemia and interstitial nephritis associated with a plasma cell dyscrasia with a monoclonal IgA gammopathy and a shifting immunoglobulin pattern that included IgG and IgA monoclonal proteins and increased urinary light chains. Osteolytic lesions were never detected and bone marrow aspirations revealed up to 10% atypical plasma cells. Various therapies often used in treating multiple myeloma only temporarily controlled the increasing renal damage. IL-2 therapy of 600,000 to 1 million units subcutaneously daily resulted in increased CD4+ T cells to normal levels, a decrease in the gammopathy, a return of renal function, energy, and weight gain, and apparently normal health status sustained for 2 years. The findings are compatible with a potentially fatal but nonmalignant immunoregulatory disorder that can be controlled by IL-2 administration.