Immune response induced by Epstein-Barr virus and Mycobacterium avium subsp. paratuberculosis peptides in current and past infectious mononucleosis: a risk for multiple sclerosis?

BACKGROUND AND PURPOSE: Infectious mononucleosis (IM) caused by Epstein-Barr virus (EBV) has been associated with increased risk of multiple sclerosis (MS). However, the mechanism linking these pathologies is unclear. Different reports indicate the association of EBV, and recently Mycobacterium avium subsp. paratuberculosis (MAP), with MS. For a better understanding of the role of these pathogens, the host response induced by selected antigenic peptides in subjects with a history of IM that significantly increases the risk of MS was investigated. METHODS: Both humoral and cell-mediated response against peptides able to induce a specific immune activation in MS patients deriving from lytic and latent EBV antigens BOLF1(305-320), EBNA1(400-413), from MAP MAP_4027(18-32), MAP_0106c(121-132) and from human proteins IRF5(424-434) and MBP(85-98) in subjects with current and past IM were examined. RESULTS: EBNA1 and MAP_0106c peptides were able to induce a humoral immune response in subjects with a history of clinical IM in an independent manner. Moreover, these peptides were capable of inducing pro-inflammatory cytokine interferon γ by CD4+ and CD8+ T lymphocytes and interleukin 6 and tumour necrosis factor α by CD14+ monocyte cells. CONCLUSION: Our results highlight that EBV and MAP may be involved independently in the same causal process leading to MS in subjects with a history of IM.

Gallbladder neoplasm: a single institution experience according to the standard current management.

AIM: The aim of this paper was to determine if an aggressive surgical approach, with an increase in R0 resections, has resulted in improved survival for patients with gallbladder cancer. Gallbladder cancer is a silent disease, despite the efforts, the prognosis remains dismal. Consensus among surgeons regarding the indications for the extent of resection, lymph node dissection, port site resection, bile duct management has not been reached. METHODS: A retrospective review of all patients with gallbladder cancer admitted during 12 years period was conducted. Sixteen patients were identified. Cases were divided into 2 cohorts surgical treated group (STG, N.=10) and non surgical treated group (NSTG, N.=6). RESULTS: In NSTG the disease was metastatic (stage IV): liver (33.3%), peritoneum (50%), liver and peritoneum (16.7%). In STG 13 procedures were performed, 6 liver resection (2 en bloc resection, 2 bisegmentectomy, 2 wedge resection) 7 cholecystectomies. 6 R1, 7 R0 resections. All the liver resections were R0. 0% mortality, 30.7% of morbidity, all the complications were managed conservatively. Length of stay was 10 days for the STG, and 5 days for the NSTG. The median overall survival was 10 months (Std Error 2.381 CI 5.333-14.667), while in the STG 16 months (Std Error 6.275 CI 3.701-28.299) and in the NSTG was 7 months (Std Error 2.381 CI 5.337-14.667) CONCLUSION: Whenever is possible radical resection with free margin (R0) must be achieved, being the only chance to treat efficiently.

Subclinical hyperthyroidism: the cardiovascular point of view.

OBJECTIVE: Subclinical hyperthyroidism (SHyper), defined as reduced thyrotropin with free hormones within the reference range, is a common medical finding, in particular in elderly people. In the last years has gained attention due to its health-related conditions, in particular at the cardiovascular level. MATERIALS AND METHODS: We searched electronic database (PubMed) and search engines (Google Scholar) of articles and reviews using the terms "subclinical hyperthyroidism", "Atrial fibrillation", Ischemic stroke", "Hypertension", Heart failure", and "Mortality". RESULTS: Subclinical hyperthyroidism was clearly associated with the onset of atrial fibrillation and, consequently, with ischemic stroke. However, the latter association is less clear. The effect on hypertension is doubtful and fair. Subclinical hyperthyroidism could increase the risk of acute heart failure, possibly by increasing heart rhythm. Data on mortality are scanty but seem to suggest a possible association, probably linked to the detrimental effect on the cardiovascular system. CONCLUSIONS: Current findings mainly described possible associations with rhythm alterations, heart failure, and stroke but the effective beneficial effects of the treatment of subclinical hyperthyroidism are still lacking.

Natural killer cell stimulatory factor (interleukin 12 [IL-12]) induces T helper type 1 (Th1)-specific immune responses and inhibits the development of IL-4-producing Th cells.

The effects exerted on the in vitro development of antigen-specific T cell lines and T cell clones by addition or neutralization of interleukin 12 (IL-12) in lymphocyte bulk culture were examined. T cell lines specific for Dermatophagoides pteronyssinus group I (Der p I) derived in the presence of IL-12 exhibited reduced ability to produce IL-4 and increased ability to produce interferon gamma (IFN-gamma), and developed into Der p I-specific CD4+ T cell clones showing a T helper type 0 (Th0)- or Th1-, instead of Th2-, like cytokine profile. In contrast, purified protein derivative (PPD)-specific T cell lines derived in the presence of anti-IL-12 antibody exhibited an increased ability to produce IL-4 and developed into PPD-specific CD4+ T cell clones showing a Th0-, instead of Th1-, like profile. The influence of IL-12 on the cytokine secretion profile of Der p I-specific T cell lines was not prevented by addition to lymphocyte bulk cultures of anti-IFN-gamma antibody, but could be at least partially inhibited by the removal from bulk cultures of CD16+ cells. Thus, IL-12 and CD16+ cells appear to have inhibitory effects on the development of IL-4-producing cells and to play an inductive role in promoting Th1-like responses.

Th2-like CD8+ T cells showing B cell helper function and reduced cytolytic activity in human immunodeficiency virus type 1 infection.

We analyzed at clonal level the functional profile of circulating or skin-infiltrating T lymphocytes from two individuals infected with the human immunodeficiency virus type 1 (HIV-1), suffering from a Job's-like syndrome (eczematous dermatitis, recurrent skin and sinopulmonary infections, and hypergammaglobulinemia E) and showing virtually no circulating CD4+ T cells. Most of the CD3+ T cell clones generated from both patients were CD4- CD8+ TCR alpha beta +. The others were CD4- CD8- TCR alpha beta + which exhibited reduced mRNA expression for the CD8 molecule or no mRNA expression for either CD4 or CD8 molecules. The great majority of both CD4- CD8+ and CD4- CD8- did not produce interferon (IFN) gamma and exhibited reduced cytolytic activity. Rather, most of them produced large amounts of both interleukin (IL) 4 and IL-5 and provided B cell helper function for IgE synthesis. These data suggest that a switch of cytolytic CD8+ T cells showing a Th1-like cytokine secretion profile to cells that make Th2-type cytokines, exhibit reduced cytolytic potential, and provide B cell helper function can occur in the course of HIV-1 infection. These cells may contribute to the reduced defense against viral infections and intracellular parasites and account for the elevated IgE serum levels, eosinophilia, and the allergic-like clinical manifestations seen in a proportion of HIV-1-infected individuals.

A genetically detoxified derivative of heat-labile Escherichia coli enterotoxin induces neutralizing antibodies against the A subunit.

Escherichia coli enterotoxin (LT) and the homologous cholera toxin (CT) are A-B toxins that cause travelers' diarrhea and cholera, respectively. So far, experimental live and killed vaccines against these diseases have been developed using only the nontoxic B portion of these toxins. The enzymatically active A subunit has not been used because it is responsible for the toxicity and it is reported to induce a negligible titer of toxin neutralizing antibodies. We used site-directed mutagenesis to inactivate the ADP-ribosyltransferase activity of the A subunit and obtained nontoxic derivatives of LT that elicited a good titer of neutralizing antibodies recognizing the A subunit. These LT mutants and equivalent mutants of CT may be used to improve live and killed vaccines against cholera and enterotoxinogenic E. coli.

CD30 expression by CD8+ T cells producing type 2 helper cytokines. Evidence for large numbers of CD8+CD30+ T cell clones in human immunodeficiency virus infection.

A large panel of CD8+ T cell clones generated from peripheral blood lymphocytes (PBL) of healthy donors or human immunodeficiency virus (HIV)-infected individuals were assessed for both cytokine secretion profile and CD30 expression and release. The great majority of CD8+ T cell clones generated from healthy individuals showed the ability to produce interferon gamma (IFN-gamma), but not interleukin 4 (IL-4), and none of them either expressed membrane CD30 or released substantial amounts of soluble CD30 (sCD30) in their supernatant. In contrast, high numbers of CD8+ T cell clones generated from HIV-infected individuals, which produced IL-4 (and IL-5) in addition to IFN-gamma or IL-4 (and IL-5) alone, expressed membrane CD30 and released detectable amounts of sCD30 in their supernatants. Indeed, CD30 expression appeared to be positively correlated with the ability of CD8+ T cell clones to produce IL-4 and IL-5 and inversely correlated with their ability to produce IFN-gamma, whereas no correlation between CD30 expression and production of IL-10 was observed. These data suggest that CD30 is a marker for CD8+ T cells that have switched to the production of type 2 helper cytokines.

Interleukin 12 induces stable priming for interferon gamma (IFN-gamma) production during differentiation of human T helper (Th) cells and transient IFN-gamma production in established Th2 cell clones.

Interleukin 12 (IL-12) facilitates the generation of a T helper type 1 (Th1) response, with high interferon gamma (IFN-gamma) production, while inhibiting the generation of IL-4-producing Th2 cells in polyclonal cultures of both human and murine T cells and in vivo in the mouse. In this study, we analyzed the effect of IL-12, present during cloning of human T cells, on the cytokine profile of the clones. The culture system used allows growth of clones from virtually every T cell, and thus excludes the possibility that selection of precommitted Th cell precursors plays a role in determining characteristics of the clones. IL-12 present during the cloning procedures endowed both CD4+ and CD8+ clones with the ability to produce IFN-gamma at levels severalfold higher than those observed in clones generated in the absence of IL-12. This priming was stable because the high levels of IFN-gamma production were maintained when the clones were cultured in the absence of IL-12 for 11 d. The CD4+ and some of the CD8+ clones produced variable amounts of IL-4. Unlike IFN-gamma, IL-4 production was not significantly different in clones generated in the presence or absence of IL-12. These data suggest that IL-12 primes the clone progenitors, inducing their differentiation to high IFN-gamma-producing clones. The suppression of IL-4-producing cells observed in polyclonally generated T cells in vivo and in vitro in the presence of IL-12 is not observed in this clonal model, suggesting that the suppression depends more on positive selection of non-IL-4-producing cells than on differentiation of individual clones. However, antigen-specific established Th2 clones that were unable to produce IFN-gamma with any other inducer did produce IFN-gamma at low but significant levels when stimulated with IL-12 in combination with specific antigen or insoluble anti-CD3 antibodies. This induction of IFN-gamma gene expression was transient, because culture of the established clones with IL-12 for up to 1 wk did not convert them into IFN-gamma producers when stimulated in the absence of IL-12. These results suggest that Th clones respond to IL-12 treatment either with a stable priming for IFN-gamma production or with only a transient low level expression of the IFN-gamma gene, depending on their stage of differentiation.

Oligomeric and subunit structure of the Helicobacter pylori vacuolating cytotoxin.

Disease-associated strains of Helicobacter pylori produce a potent toxin that is believed to play a key role in peptic ulcer disease in man. In vitro the toxin causes severe vacuolar degeneration in target cells and has thus been termed VacA (for vacuolating cytotoxin A). Cytotoxic activity is associated with a > 600-kD protein consisting of several copies of a 95-kD polypeptide that undergoes specific proteolytic cleavage after release from the bacteria to produce 37- and 58-kD fragments. Quick freeze, deep etch electron microscopy has revealed that the native cytotoxin is formed as regular oligomers with either six- or seven-fold radial symmetry. Within each monomer, two domains can clearly be distinguished, suggesting that the 37- and 58-kD fragments derive from proteolytic cleavage between discrete subunits of the monomer. Analysis of preparations of the toxin that had undergone extensive cleavage into the 37- and 58-kD subunits supports this interpretation and reveals that after cleavage the subunits remain associated in the oligomeric structure. The data suggest a structural similarity with AB-type toxins.

Ability of HIV to promote a TH1 to TH0 shift and to replicate preferentially in TH2 and TH0 cells.

Both interferon gamma (IFN-gamma) produced by T helper 1 (TH1) lymphocytes and interleukin-4 (IL-4) produced by TH2 lymphocytes were reduced in either bulk circulating mononuclear cells or mitogen-induced CD4+ T cell clones from the peripheral blood of individuals infected with human immunodeficiency virus (HIV). There was a preferential reduction in clones producing IL-4 and IL-5 in the advanced phases of infection. However, enhanced proportions of CD4+ T cell clones producing both TH1-type and TH2-type cytokines (TH0 clones) were generated from either skin-infiltrating T cells that had been activated in vivo or peripheral blood T cells stimulated by antigen in vitro when cells were isolated from HIV-infected individuals. All TH2 and most TH0 clones supported viral replication, although viral replication was not detected in any of the TH1 clones infected in vitro with HIV. These results suggest that HIV (i) does not induce a definite TH1 to TH2 switch, but can favor a shift to the TH0 phenotype in response to recall antigens, and (ii) preferentially replicates in CD4+ T cells producing TH2-type cytokines (TH2 and TH0).

Mutants of pertussis toxin suitable for vaccine development.

Immunization with chemically detoxified pertussis toxin can prevent severe whooping cough with an efficacy similar to that of the cellular pertussis vaccine, which normally gives unwanted side effects. To avoid the reversion to toxicity and the loss of immunogenicity that may follow chemical treatment of pertussis toxin, inactive toxins were constructed by genetic manipulation. A number of genetically engineered alleles of the pertussis toxin genes, constructed by replacing either one or two key amino acids within the enzymatically active S1 subunit, were introduced into the chromosome of strains of Bordetella pertussis, B. parapertussis, and B. bronchiseptica. These strains produce mutant pertussis toxin molecules that are nontoxic and immunogenic and that protect mice from the intracerebral challenge with virulent Bordetella pertussis. Such molecules are ideal for the development of new and safer vaccines against whooping cough.

Identification of vaccine candidates against serogroup B meningococcus by whole-genome sequencing.

Neisseria meningitidis is a major cause of bacterial septicemia and meningitis. Sequence variation of surface-exposed proteins and cross-reactivity of the serogroup B capsular polysaccharide with human tissues have hampered efforts to develop a successful vaccine. To overcome these obstacles, the entire genome sequence of a virulent serogroup B strain (MC58) was used to identify vaccine candidates. A total of 350 candidate antigens were expressed in Escherichia coli, purified, and used to immunize mice. The sera allowed the identification of proteins that are surface exposed, that are conserved in sequence across a range of strains, and that induce a bactericidal antibody response, a property known to correlate with vaccine efficacy in humans.

Efficacy and safety of full-thickness resection device based on over-the-scope clip system for resecting of gastric lesions in selected patients. Case series from a referral center for gastrointestinal diseases treatment and literature overview.

Since gastroduodenal FTRD system is commercially available, several data have been reported in Literature concerning duodenal full-thickness resections, whereas few cases of gastric full-thickness resections has been described. In this case series We report three patients treated with this innovative tool for resecting lesions of the gastric wall. The indications ranged notably: a neuroendocrine tumor in a difficult to treat environment in the first case, a recurrent adenocarcinoma in a poorly surgical candidate patient in the second case and a pre-pyloric lesion for the third patient. In the third patient, a complete pyloric stenosis due to the clip deployment occurred. Clinical success rate was 100%. Even if current Literature is still poor of articles dealing with gastric full-thickness resection device based on over-the-scope-clip system. Our case series show how this novel tool might be take into consideration for whenever both surgery and standard endoscopic resection techniques are poorly feasible.

Life-threatening bleeding for a large cameron ulcer. A novel description of a tailored-surgical strategy: report of a case and literature overview.

Hiatal hernias (HHs) are usually divided into two main groups: sliding and para-esophageal (torsional) ones. Sometimes patients presenting HHs experience progressive anemia, whereas rarely an acute anemia with melena or hematemesis can occur. In such cases a Cameron ulcer should be suspected and a careful esophago-gastro-duodenoscopy (EGDS) with a meticulous inspection of the mucosal folds along the neck of the hernia is the best examination in order to find out the ulcer itself. In front of massive hemorrhage due to a Cameron erosion, the first aim should be the control of the bleeding itself, in order to ree1Romastablish hemodynamic stability. The Authors report the case of a 72-year-old man presenting a severe bleeding secondary to a large Cameron ulcer in a para-esophageal hiatal hernia. Firstly, a combined medical-endoscopic therapy was tried; the patient underwent transfusions of pooled red blood cells and endovenous anti-acid therapy combined with an operative endoscopic treatment; unfortunately this initial approach failed, therefore the patient was referred to surgery. The surgeons realized a minimally invasive atypical gastric resection associated with the HH repair; the post-operative course was uneventful and no other rebleeding episodes occurred. The urgency treatment of a life-threatening bleeding for Cameron ulcers remains a very challenging problem as no univocal and standardized recommendation has been described in literature since now. In this case-report the Authors make an overview of the current literature on the treatment of Cameron ulcers, describing a novel surgical technique for massive upper gastro-intestinal bleeding secondary to these lesions.

Homologous HSV1 and alpha-synuclein peptides stimulate a T cell response in Parkinson's disease.

Environmental factors are implicated in the development of Parkinson's disease (PD). The aim of this study is to investigate the role of cell-mediated immunity upon a specific immune-stimulation with HSV-1 and human alpha-synuclein homologues peptides by using the intracellular cytokine method on Parkinson's patients and healthy controls. The study showed, for the first time, a specific response to TNF-α CD8, CD4 and NK cells after stimulation in PD patients. Our data show a possible role of the immune system in the pathogenesis of Parkinson's disease, and that HSV-1 infections may lead to a progression of the disease.

Underserved populations and bacterial and protozoal sexually transmitted infections: a lost health-care opportunity.

OBJECTIVE: The purpose of our review is an update about the burden of sexually transmitted infections (STIs) among various types of underserved populations, such as migrants, substance abusers, homeless and incarcerated inmates. First-line test and treatment based on the latest available evidence according to the revised guidelines of Centers for Disease Control and Prevention have also been considered. MATERIALS AND METHODS: We performed a comprehensive research using scientific databases such as Medline and Pubmed, followed by a review of citations and reference list. A consultation with other experts in the management of the various subpopulations was also conducted. RESULTS: Health-care is often influenced by social determinants, which play a vital role in the diffusion of STIs. The consequence is a socio-economical and ethnic disparity in the rate of STIs. Early screening and treatment of STIs should be implemented in clinical practice, starting from marginalized social groups, which are the most affected by this health problem. CONCLUSIONS: In the literature, there are very few papers containing information on STIs prevalence in various types of underserved populations, such as migrants, substance abusers, homeless and incarcerated inmates. The availability of more accurate epidemiological data is needed. In these groups, the most relevant barrier is the lower perception of health-care need, with an underestimation of risk and symptoms of STIs, causing a retard of diagnosis and health-care provision and use. For these populations, targeted interventions are needed, particularly on unaware people, responsible for most STIs transmissions.

Peripheral blood CD8+ T-cell profiles in patients with psoriatic arthritis: a cross-sectional case-control study.

OBJECTIVE: While CD4+ T-cells are traditionally regarded as the main pathogenic T-cell subpopulation in psoriatic arthritis (PsA), the role of circulating CD8+ T-cells remains poorly characterized. We evaluated the differential representation of CD8+ T-cell subpopulations in peripheral blood (PB) of PsA patients. PATIENTS AND METHODS: CD8+IL-17+, CD8+IFNγ+ and CD8+IL-17-IL-22+ T-cells were evaluated by flow-cytometry in 25 consecutive PsA patients, 7 rheumatoid arthritis (RA) patients, 16 patients with psoriasis, and 26 healthy controls (HC). RESULTS: We observed a significant expansion of circulating IFN-γ producing CD8+ T-cells in PsA when compared to psoriasis [21.2 (6.9-55.8)% vs. 3.8 (0.7-11.8)%, p < 0.0001] and HC samples [21.2 (6.9-55.8)% vs. 4.05 (0.44-19.8)%, p < 0.0001]. A frequency of circulating IFN-γ producing CD8+T-cells ≥ 9% distinguished PsA from psoriasis patients with a specificity of 84% and a sensitivity of 87.5% [AUC = 0.9 (0.80-0.99), p < 0.0001]. In addition, we found a significant expansion of circulating IL-17 producing CD8+ T cells in RA patients when compared to PsA, psoriasis and HC samples. By contrast, there were no significant between-group differences in the prevalence of circulating IL-22 producing CD8+ T-cells. In PsA patients there was a significant correlation between number of swollen joints and frequency of circulating IFN-γ producing CD8+ T-cells, and between extent and severity of psoriasis and frequency of circulating IL-17 producing CD8+ T-cells. CONCLUSIONS: Circulating IFNγ-producing CD8+ T-cells are raised in PsA when compared to psoriasis, suggesting a potential pathogenetic involvement of CD8+ T-cells and IFNγ production in chronic joint inflammation and damage. The significant enrichment of circulating IL-17 producing CD8+ T-cells in RA when compared to PsA warrants functional characterization and confirmation in larger studies. We found no significant enrichment of circulating IL-22 producing CD8+ T-cells in PsA, RA and psoriasis.

The burden of HIV-associated neurocognitive disorder (HAND) in post-HAART era: a multidisciplinary review of the literature.

OBJECTIVE: The purpose of the present multidisciplinary review is to give an updated insight into the most recent findings regarding the pathophysiology, diagnosis and therapeutics of HIV-associated neurocognitive disorder (HAND). MATERIALS AND METHODS: We performed a comprehensive search, through electronic databases (Pubmed - MEDLINE) and search engines (Google Scholar), of peer-reviewed publications (articles and reviews) and conferences proceedings on HAND pathophysiology, diagnosis, and therapy, from 1999 to 2016. RESULTS: It seems to be increasingly clear that neurodegeneration in HIV-1 affected patients is a multi-faceted disease involving numerous factors, from chronic inflammation to central nervous system (CNS) compartmentalization of HIV. Diagnosis of HAND may benefit from both laboratory analysis and advanced specific neuroimaging techniques. As regards HAND therapy, modified HAART combinations and simplification strategies have been tested, while novel exciting frontiers seem to involve the use of nanoparticles with the ability to cross the Blood-Brain Barrier (BBB). CONCLUSIONS: Albeit highly active antiretroviral therapy (HAART) allowed a major decrease in morbidity and mortality for AIDS patients, CNS involvement still represents a challenge in HIV patients even today, affecting up to 50% of patients with access to combination antiretroviral therapy (cART). Future studies will have to focus on CNS compartmentalization, drugs' ability to penetrate and suppress viral replication in this compartment, and on new approaches to reduce HIV-associated neuroinflammation.

HPV16 E7 protein associates with the protein kinase p33CDK2 and cyclin A.

E7 is the major transforming protein of human papillomavirus type 16 (HPV16). It has been found to associate with the retinoblastoma protein Rb1. We investigated whether HPV16 E7 protein was associated with other cellular proteins, in particular with those involved in cell cycle control. Immunoprecipitates from CaSki cell extracts with an anti E7 monoclonal antibody contained a histone H1 kinase. Recombinant E7, synthesized in yeast, when mixed with protein extracts from epithelial cells bound histone H1 kinase activity in vitro. The in vivo and the in vitro-formed E7-kinase complex had the same periodicity of activity during the cell cycle, being most active in S and G2/M. Immunoblotting of E7 immunoprecipitates with an antibody raised against the p33CDK2, revealed a 33 kDa protein band not detected by an anti-p34cdc2 antibody, suggesting that the E7-associated kinase activity is due to the p33CDK2. The interaction appears to be via cyclin A, since probing of similar immunoblots showed a 50 kDa band corresponding to cyclin A. The association of E7 with cyclin A appeared to be direct, not involving Rb 1 or other proteins.

Assessment of chemokine receptor expression by human Th1 and Th2 cells in vitro and in vivo.

The preferential association of some chemokine receptors with human Th1 or Th2 cells has recently been reported. In this study, the expression of CCR3, CCR5, CXCR3, and CXCR4 were analyzed by flow cytometry in three distinct in vitro models of Th1/Th2 polarization, activated naive and memory T cells, and T-cell clones, in which the intracellular synthesis of interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) and the surface expression of CD30 and LAG-3 were also assessed. Moreover, by using immunohistochemistry the in vivo expression of CCR3, CCR5, CXCR3, and CXCR4 was examined in the gut of patients suffering from Crohn's disease, a Th1-dominated disorder, and in the skin of patients suffering from systemic sclerosis, a Th2-dominated disorder. CCR5 and LAG-3 exhibited the same pathway of Th1 association, whereas CXCR3 did not discriminate between Th1- and Th2-dominated responses. On the other hand, CCR3 was found only occasionally in a small proportion of allergen-specific memory T cells with Th2/ThO profile of cytokine production in vitro. However, it was neither seen in Th2-polarized activated naive T cells nor in established Th2 clones and could be detected in vivo only on non-T cells. Finally, whereas CXCR4 expression was not limited to Th2 cells in vivo, it was markedly up-regulated by IL-4 and down-regulated by IFN-gamma in vitro. Thus, the results of this study confirm the existence of flexible programs of chemokine receptor expression during the development of Th1 and Th2 cells. However, caution is advised in interpreting these receptors as surrogate markers of a given type of effector response.