Flow cytometry in formamide treated cells

The use of formamide for the study in flow cytometry of cell cycle phases, by DNA content measurement in human cancer cell lines, was recently published. In this manuscript, we verify the possibility of extending the procedure to simultaneous analysis of other parameters. The results obtained, here reported, show that the treatment of samples by formamide is compatible with the simultaneous detection of DNA content and surface phenotypes, with quantification of replicating DNA and with measurement of cells with fractional content of DNA. For each of these three applications, we have adapted the procedure to gain simple, reproducible and above all advantageous protocols. Regarding the simultaneous analysis of DNA content and phenotyping the use of formamide achieves optimal DNA stoichiometric staining (C.V. < 3; G2/G1 ratio = 2 ± 0.05) and sufficient maintenance of physical parameters and membrane fluorescence. In the study of duplicating DNA labeled with click chemistry, our procedure eliminates paraformaldehyde (PFA) fixation improving the DNA stoichiometric staining and allows the use of 7-aminoactinomycin D (7-AAD) preserving the Alexa Fluor 488 quantum efficiency. Concerning the detection of cells with fractional content of DNA, permeabilization and fixation by formamide gives the advantage of resolve on linear scale sub-G1 cells from debris and to allow optimal sample recovery (>90%) which is essential in the study of cell necrobiology. Cells treatment by formamide, suitably modified for different applications, can be used to prepare cell samples for flow cytometry analyses that go far beyond stoichiometric staining of DNA.

PARP inhibitors enhance replication stress and cause mitotic catastrophe in MYCN-dependent neuroblastoma

High-risk and MYCN-amplified neuroblastomas are among the most aggressive pediatric tumors. Despite intense multimodality therapies, about 50% of these patients succumb to their disease, making the search for effective therapies an absolute priority. Due to the important functions of poly (ADP-ribose) polymerases, PARP inhibitors have entered the clinical settings for cancer treatment and are being exploited in a variety of preclinical studies and clinical trials. PARP inhibitors based combination schemes have also been tested in neuroblastoma preclinical models with encouraging results. However, the expression of PARP enzymes in human neuroblastoma and the biological consequences of their inhibition remained largely unexplored. Here, we show that high PARP1 and PARP2 expression is significantly associated with high-risk neuroblastoma cases and poor survival, highlighting its previously unrecognized prognostic value for human neuroblastoma. In vitro, PARP1 and 2 are abundant in MYCN amplified and MYCN-overexpressing cells. In this context, PARP inhibitors with high 'PARP trapping' potency, such as olaparib or talazoparib, yield DNA damage and cell death preceded by intense signs of replication stress. Notwithstanding the activation of a CHK1-CDC25A replication stress response, PARP-inhibited MYCN amplified and overexpressing cells fail to sustain a prolonged checkpoint and progress through mitosis in the presence of damaged DNA, eventually undergoing mitotic catastrophe. CHK1-targeted inhibition of the replication stress checkpoint exacerbated this phenotype. These data highlight a novel route for cell death induction by PARP inhibitors and support their introduction, together with CHK1 inhibitors, in therapeutic approaches for neuroblastomas with high MYC(N) activity.

New use for an old reagent: Cell cycle analysis of DNA content using flow cytometry in formamide treated cells

Formamide has long been one of the most widely used reagents in the study of nucleic acids. However, the use of formamide for treating cells to be analyzed by flow cytometry is a recent development and is restricted to measuring telomere lengths by flow-FISH. In this field, we have published several papers in order to observe the effects of formamide treatment on cells at room temperature. We therefore discovered that, with suitable modifications, a short and simple incubation in this ionizing solvent facilitates cell cycle analysis by flow cytometry, equivalent or superior to that obtained with treatments in alcohol, acetone or detergent in hypotonic solution. Even using a bulky and problematic stain (low quantum efficiency and G-C base preference), such as 7-aminoactinomycin D (7-AAD) which, on the other hand, has the advantage of being excited at 488 nm and does not bind to the RNA, it is possible to obtain excellent coefficients of variation and (G2-M) mode/(G0-G1) mode ratios. These parameters, especially if stained cells are washed before acquisition, arrive at optimal values. It is noteworthy that the ability to wash the cells stained for DNA content analysis without affecting the stoichiometry of the staining has not been described elsewhere in the literature. With formamide treatment the doublets are practically absent, sample recovery is efficient, as well as the preservation of physical parameters, and the stained cells can be stored for at least 10 days at room temperature before acquisition. © 2016 International Society for Advancement of Cytometry.

Dysregulated extracellular signal-regulated kinase signaling associated with impaired B-cell receptor endocytosis in patients with common variable immunodeficiency

BACKGROUND

Common variable immunodeficiency (CVID) is a heterogeneous disorder characterized by B-cell dysfunction and, in a subgroup, by expansion of CD21(low) B cells. The CD21(low) B cells display defects in early B-cell receptor (BCR) signaling resembling those of anergic B cells.

OBJECTIVE

We sought to investigate whether B cells from patients with CVID, like anergic B cells, have defects in extracellular signal-regulated kinase (ERK) phosphorylation and in endocytic trafficking of the BCR.

METHODS

Using flow cytometry, we evaluated phosphorylated ERK (pERK) expression and internalization of cross-linked BCR in B-cell subsets. The localization of internalized BCR to lysosome-associated membrane protein 1-positive late endosomes was evaluated with confocal microscopy.

RESULTS

Constitutive pERK levels were increased in naive and IgM(+) memory B cells of patients with CVID compared with those of healthy donors, whereas the pERK increment induced by BCR cross-linking was relatively reduced. Intravenous immunoglobulin administration enhanced these anomalies, but they appeared to be intrinsic to B cells from patients with CVID. Cross-linking-induced BCR endocytosis was decreased in the IgM(+) memory B cells, especially in those with a CD21(low) phenotype, but not in the naive B cells of patients with CVID with CD21(low) expansion. Internalized BCR localized normally to late endosomes. Pharmacologic inhibition of ERK phosphorylation suppressed BCR endocytosis in B cells of healthy patients and those with CVID.

CONCLUSIONS

The B cells of patients with CVID with CD21(low) B-cell expansion resemble anergic B cells based on high constitutive pERK expression. The IgM(+) memory B cells of these patients, especially those that are CD21(low), have a defect in BCR endocytosis seemingly caused by dysregulated ERK signaling.

Correlation between terminal restriction fragments and flow-FISH measures in samples over wide range telomere lengths

OBJECTIVES

Terminal restriction fragment (TRF) analysis of human telomeres was used to calibrate flow-fluorescence in situ hybridization (FF) measures of telomere lengths to expand the range of measures and increase power of resolution of our previously published protocol. TRF data used as the gold standard should be obtained by electrophoresis with suitable resolution applied to appropriately isolated genomic DNA. When we considered TRF attained by correct methods, we found our method to be insufficiently accurate, thus we have reviewed our previously published FF protocol to obtain the best coefficient of determination (r(2)) between our experimental results and valid TRF lengths.

MATERIALS AND METHODS

Using human telomere-specific PNA probe, Cy5-OO-(CCCTAA)3 , we measured telomere lengths of continuous cell line and of peripheral blood lymphocytes by FF. We modified hybridization, stringency, negative control handling, stoichiometric DNA staining and telomere fluorescence assessment of the protocol.

RESULTS

We realized a procedure with increased power of resolution, improved TRF versus FF r(2) values that allowed simultaneous analysis of DNA and telomere duplication. Notwithstanding multiple steps in formamide sampling, recovery was satisfactory.

DISCUSSION

The reviewed FF protocol appeared at least as suitable as the TRF method. Measures obtained by TRF can be affected by chromosome end variability, DNA fragmentation, incomplete digestion and unsuitable electrophoresis. In contrast, the FF technique analyses telomeric sequences confined to preserved nuclei thus overcome most previous limitations. As yet, however, the FF telomere measure cannot be performed together with immunophenotyping and/or generation study by the dye dilution method.

Telomere-dependent replicative senescence of B and T cells from patients with type 1a common variable immunodeficiency

A subset of patients with common variable immunodeficiency (CVID), group 1a of the Freiburg classification, is characterized by increased B cells expressing low levels of CD21 (CD21(low) ), lymphoproliferation and autoimmunity. The CD21(low) B cells have been shown to be profoundly anergic, and defects of BCR-mediated calcium signaling and of T cells have been described in CVID 1a. We found that also the classical naïve B cells from CVID 1a patients, but not from CVID non-1a patients, proliferated poorly. The B cells of CVID 1a patients had a reduced capacity to divide reminiscent of the proliferative arrest associated with replicative senescence. Thus, we investigated whether lymphocyte dysfunction in CVID 1a was related to telomere-dependent replicative senescence, and found that both the B and the T cells from CVID 1a patients had significantly shorter telomeres compared with B and T cells from CVID non-1a patients. Telomere lengths in B and T cells were significantly correlated, indicating that the rate of telomere attrition in lymphocytes is an individual characteristic of CVID patients. Our findings suggest that telomere-dependent replicative senescence contributes to the immune dysfunction of CVID 1a patients, and may provide an important clue for a better understanding of the pathogenesis of CVID.

MYCN sensitizes human neuroblastoma to apoptosis by HIPK2 activation through a DNA damage response

MYCN amplification occurs in approximately 20% of human neuroblastomas and is associated with early tumor progression and poor outcome, despite intensive multimodal treatment. However, MYCN overexpression also sensitizes neuroblastoma cells to apoptosis. Thus, uncovering the molecular mechanisms linking MYCN to apoptosis might contribute to designing more efficient therapies for MYCN-amplified tumors. Here we show that MYCN-dependent sensitization to apoptosis requires activation of p53 and its phosphorylation at serine 46. The p53(S46) kinase HIPK2 accumulates on MYCN expression, and its depletion by RNA interference impairs p53(S46) phosphorylation and apoptosis. Remarkably, MYCN induces a DNA damage response that accounts for the inhibition of HIPK2 degradation through an ATM- and NBS1-dependent pathway. Prompted by the rare occurrence of p53 mutations and by the broad expression of HIPK2 in our human neuroblastoma series, we evaluated the effects of the p53-reactivating compound Nutlin-3 on this pathway. At variance from other tumor histotypes, in MYCN-amplified neuroblastoma, Nutlin-3 further induced HIPK2 accumulation, p53(S46) phosphorylation, and apoptosis, and in combination with clastogenic agents purged virtually the entire cell population. Altogether, our data uncover a novel mechanism linking MYCN to apoptosis that can be triggered by the p53-reactivating compound Nutlin-3, supporting its use in the most difficult-to-treat subset of neuroblastoma.

Improved procedure for the measurement of telomere length in whole cells by PNA probe and flow cytometry

OBJECTIVES

Peptide nucleic acid (PNA) probes hybridize to denatured telomeric sequences in cells permeabilized in hot formamide. In reported protocols, the hybridization was conducted in solutions with high formamide concentrations to avoid the DNA renaturation that can hamper binding of the oligo-PNA probe to specific sequences. We postulated that telomeric DNA, confined in the nuclear microvolume, is not able to properly renature after hot formamide denaturation. Therefore, to improve hybridization conditions between the probe and the target sequences, it might be possible to add probe to sample after the complete removal of formamide.

MATERIALS AND METHODS

After telomeric DNA denaturation in hot formamide solution and several washes to remove the ionic solvent, cells were hybridized overnight at room temperature with human telomere-specific PNA probe conjugated with Cy5 fluorochrome, Cy5-OO-(CCCTAA)(3) . After stringency washes and staining with ethidium bromide, the cells were analysed by flow cytometry and by using a confocal microscope.

RESULTS

Using three continuous cell lines, different in DNA content and telomere length, and resting human peripheral blood T and B lymphocytes, we demonstrated that the oligo-PNA probe hybridized to telomeric sequences after complete removal of formamide and that in the preserved nucleus, telomeric sequence denaturation is irreversible.

CONCLUSION

According to our experience, oligo-PNA binding results is efficient, specific and proportional to telomere length. These, our original findings, can form the technological basis of actual in situ hybridization on preserved whole cells.

Immunophenotyping and DNA content analysis of acetone-fixed cells

The flow acetone staining technique (FAST) allows one to concurrently study physical cell features revealed by light-scatter analysis, surface/nuclear phenotypes, and cellular DNA content. Thus, diverse subpopulations of proliferating cells can be identified in heterogeneous populations by their immunophenotype and their cell cycle status, and DNA ploidy can be assessed. Acetone, a coagulant (precipitating) fixative that also has the ability to permeabilize cell membranes, is widely used in static cytometry, but rarely in flow cytometry because of its undesirable effects, namely causing cell shrinkage. Nevertheless, when employed under proper temperature conditions (approximately 8 degrees C), it preserves cellular physical features and immunophenotype well, and is compatible with stoichiometric DNA staining and accurate measurement of DNA content. Due to these virtues of FAST, the method provides useful approaches for cell biology and hematology/oncology studies.

Flow acetone-staining technique: a highly efficient procedure for the simultaneous analysis of DNA content, cell morphology, and immunophenotype by flow cytometry

The accurate determination of cell cycle, immunophenotypes and morphology at single-cell level is not fully achieved by current flow cytometry protocols. Acetone, a coagulant fixative/permealizing agent, is widely used in static cytometry, but is impractical in flow cytometry because of its shrinking effect. We sought for conditions of acetone treatment that could permit the simultaneous analysis of physical parameters, surface and intracellular immunostaining, and DNA content. We evaluated different experimental conditions (concentration, duration of fixation, temperature, presence of proteins) to test the capacity of acetone fixation/permeabilization to preserve cell physical parameters (forward and side scatters, FSC, and SSC) and immunophenotyping while allowing stoichiometric DNA staining. The commonly used ethanol fixation technique was used as reference method. To detect phenotypes and DNA content simultaneously, we employed 7-aminoactinomycin D (7-AAD) as "intercalating" dye for DNA in spite of, or just for, its controversial ability in stoichiometric DNA staining. Cells were resting peripheral blood monucleated cells (PBMCs), T- and B-cell blasts obtained by PBMCs stimulation, and the human cell lines Ramos and Shep. Acetone fixation, preserving both the recovery and the physical parameters of cells, is drastically influenced by temperature of treatment and is practicable only when the protocol is realized at 8 degrees C. Under this condition, acetone maintains the immunophenotypic fluorescences (realized before or after the fixation) better than ethanol. Stoichiometric DNA staining of acetone processed cells, the variation coefficients (CV) of frequency distributions of G1/G0 and G2/M phases, the modes ratio of these distributions and doublets generation are at least comparable to those obtained with ethanol treatment. The assay developed in the present study, that we called flow acetone-staining technique (FAST), accurately analyzes cell cycle, physical parameters and immunophenotypes in heterogenous cell populations, and thus provides a useful tool for cytomics.

Control of human herpes virus type 8-associated diseases by NK cells

The "natural killer" (NK) cells preferentially kill targets lacking surface major histocompatibility complex class I (MHC-I) molecule expression. NK cells recognize these targets through membrane receptors, which can trigger activating or inhibitory signals for killing. Several tumors or virus-infected cells downregulate MHC-I expression as a mechanism to evade recognition and killing by cytotoxic T lymphocytes (CTL). They, however, become targets for NK cells cytotoxic activity. NK cell activity is reduced during disease progression in human immunodeficiency virus (HIV) infection, and in individuals with AIDS-associated tumors linked with infection by the oncogenic human herpes virus type-8 (HHV8), including Kaposi's sarcoma (KS) and primary effusion lymphomas (PEL). We have demonstrated that AIDS-related KS (AIDS-KS) is characterized by an increased expression of inhibitory receptors by T lymphocytes, and that HIV-non-infected patients with KS (classic KS, C-KS) have a substantial number of NK cells bearing these same receptors. NK cells from patients with C-KS are normally equipped with cytolytic molecules including granzyme A and perforin. However, the cytotoxic activity of NK cells is reduced in patients with C-KS, AIDS-KS, or PEL patients, who are all infected by the HHV8, and this correlates with disease severity. Moreover, we have found that HHV8-infected cell lines established from PELs have a reduced surface expression of MHC-I molecules and are sensitive to the lysis mediated by NK cells. Since PEL cells express the same HHV8 latency program as KS cells, these data point to MHC-I downregulation by HHV8 as a primary immune evasion mechanism against CTL responses, further reinforced by upregulation of inhibitory receptors on T and NK cells in the setting of HIV and/or HHV8 infection. Thus, studies on killing receptor regulation and signaling in T and NK cells may shed light on the pathogenesis of HHV8-associated tumors both in HIV-infected or -noninfected patients.

Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethylpyrimidine) induces apoptosis of freshly isolated human T lymphocytes, bypassing CD95/Fas molecule but involving its intrinsic pathway

Pyrimethamine (2,4-diamino-5-p-chlorophenyl-6-ethyl-pyrimidine), a folic acid antagonist, may exert, in addition to antiprotozoan effects, immunomodulating activities, including induction of peripheral blood lymphocyte apoptosis. However, the molecular mechanisms underlying this proapoptotic activity remain to be elucidated. Here we show that pyrimethamine, used at a pharmacologically relevant concentration, induced per se apoptosis of activated lymphocytes via the activation of the caspase-8- and caspase-10-dependent cascade and subsequent mitochondrial depolarization. Importantly, this seems to occur independently from CD95/Fas engagement. The proapoptotic activity of pyrimethamine was further confirmed in a patient with autoimmune lymphoproliferative syndrome, an immune disorder associated with a defect of Fas-induced apoptosis. In this patient, pyrimethamine treatment resulted in a "normalization" of lymphocyte apoptosis with a significant amelioration of laboratory parameters. Altogether, these results suggest a mechanism for pyrimethamine-mediated apoptosis that seems to bypass CD95/Fas engagement but fully overlaps CD95/Fas-induced subcellular pathway. On these bases, a reappraisal of the use of pyrimethamine in immune lymphoproliferative disorders characterized by defects in CD95/Fas-mediated apoptosis should be taken into account.

Hepatitis C virus drives the unconstrained monoclonal expansion of VH1-69-expressing memory B cells in type II cryoglobulinemia: a model of infection-driven lymphomagenesis

Chronic hepatitis C virus infection causes B cell lymphoproliferative disorders that include type II mixed cryoglobulinemia and lymphoma. This virus drives the monoclonal expansion and, occasionally, the malignant transformation of B cells producing a polyreactive natural Ab commonly encoded by the V(H)1-69 variable gene. Owing to their property of producing natural Ab, these cells are reminiscent of murine B-1 and marginal zone B cells. We used anti-Id Abs to track the stages of differentiation and clonal expansion of V(H)1-69(+) cells in patients with type II mixed cryoglobulinemia. By immunophenotyping and cell size analysis, we could define three discrete stages of differentiation of V(H)1-69(+) B cells: naive (small, IgM(high)IgD(high)CD38(+)CD27(-)CD21(high)CD95(-)CD5(-)), "early memory" (medium-sized, IgM(high)IgD(low)CD38(-)CD27(+)CD21(low)CD95(+)CD5(+)), and "late memory" (large-sized, IgM(low)IgD(low-neg)CD38(-)CD27(low)CD21(low-neg)CD5(-)CD95(-)). The B cells expanded in cryoglobulinemia patients have a "memory" phenotype; this fact, together with the evidence for intraclonal variation, suggests that antigenic stimulation by hepatitis C virus causes the unconstrained expansion of activated V(H)1-69(+) B cells. In some cases, these cells replace the entire pool of circulating B cells, although the absolute B cell number remains within normal limits. Absolute monoclonal V(H)1-69(+) B lymphocytosis was seen in three patients with cryoglobulinemia and splenic lymphoma; in two of these patients, expanded cells carried trisomy 3q. The data presented here indicate that the hepatitis C virus-driven clonal expansion of memory B cells producing a V(H)1-69(+) natural Ab escapes control mechanisms and subverts B cell homeostasis. Genetic alterations may provide a further growth advantage leading to an overt lymphoproliferative disorder.

Human peripheral B cells: a different cytometric point of view

BACKGROUND

Human peripheral B lymphocytes, analyzed by current flow cytometers, frequently show complex patterns of morphological and fluorescence signals. However, fluorescence intensity values are commonly reported without any correlation to the cell surface area. We propose a different approach, based on the evaluation of the ratio of phenotype fluorescence intensity to forward scatter intensity, to determine the apparent fluorescence density of surface molecules.

METHODS

Starting from list mode acquired data, and after logical gating of live B cells, the analytical procedure suggests a serial scanning of the FSC versus SSC plot to obtain apparent fluorescence density of progressively larger cells.

RESULTS

This method, applied to normal human peripheral B lymphocytes, was able to detect the presence of steady and modulated (with respect to cell size) fluorescence densities for a variety of surface molecules. B cells from patients with B cell disorders displayed interesting alterations of the phenotype density values and distributions.

CONCLUSIONS

Our preliminary data show that, in human B cell cytometry, the apparent fluorescence density based method allows one to recognize variations in fluorescence intensities solely due to cell size differences and to disclose patterns of expression not detectable by the conventional intensity based approach.

A unified procedure for conservative (morphology) and integral (DNA and immunophenotype) cell staining for flow cytometry

BACKGROUND

Current methods for multiparameter DNA flow cytometry suffer from several limitations. These include significant modifications of cell morphological parameters, the impossibility to counterstain cells with certain fluorochromes, and laborious tuning of the instrument that, for some procedures, must be equipped with an ultraviolet (UV) laser. To overcome these problems, we developed a novel method for the simultaneous analysis of morphological parameters, four-color immunophenotyping, and stoichiometric DNA labeling using a bench-top flow cytometer.

METHODS

The method consists of a mild permeabilization/fixation treatment at room temperature, followed by labeling with fluorochrome-conjugated monoclonal antibodies (mAbs) and with the DNA dye 7-aminoactinomycin D (7-AAD) at 56 degrees C.

RESULTS

Using this method, we analyzed resting peripheral blood mononucleated cells (PBMC), proliferating T cells cultured in the presence of interleukin-2 (IL-2), and lymphoblastoid B cells. Lymphocytes, monocytes, and lymphoblasts treated by this procedure retained differential light scattering (DLS) characteristics virtually identical to those of untreated cells. This allowed regions to be drawn on forward scatter (FSC) and side scatter (SSC) cytograms resolving different cell populations. DLS were preserved well enough to distinguish large lymphoblasts in the S or G2/M phases from small G0/G1 cells. Also, stainability with fluorescein-isothiocyanate (FITC), R-phycoerythrin (PE), allophycocyanin (APC)-conjugated mAbs was generally preserved. DNA labeling with 7-AAD was of quality good enough to permit accurate cell cycle analysis.

CONCLUSIONS

The method described here, which we called integral hot staining (IHS), represents a very simple, reproducible, and conservative assay for multiparameter DNA analysis using a bench-top flow cytometer. Last but not least, the cytometer tuning for multiparameter acquisition is straightforward.

Peptide analogues as a strategy to induce tolerance in T cells with indirect allospecificity

BACKGROUND

It has been demonstrated that indirect recognition of allogeneic MHC molecules might play an important role in provoking graft rejection. Although direct recognition of allogeneic molecules on antigen presenting cells of the graft may induce a state of tolerance, the continuous presentation of processed alloantigens by specialized antigen presenting cells does not allow the same phenomenon to occur. Tolerance to interleukin-2 secreting T cells can be achieved in different ways, among these is the exposure to mutants of the wild type allopeptide. We have investigated whether peptide analogues of the allopeptide can induce tolerance in T cells with indirect allospecificity.

METHODS

T cell clones with indirect anti-HLA-A2-specificity generated from a HLA-A2-DRB1*1502+ patient who chronically rejected a HLA-A2-expressing kidney allograft were used for this study. Nine peptide analogues of HLA-A2 (residues: 103-120) were produced with single amino acid substitutions at the putative T cell receptor for antigen contact positions. Their effect on the proliferation of a panel of T cell clones was evaluated.

RESULTS

Peptide analogues and wild type peptide had similar capacity to bind to the restriction molecule HLA-DRB1*1502. Co-presentation of the peptide analogues 111R/A, H, K and 114H/K, with the wild type peptide inhibited T cell responses, indicative of antagonism. In addition, one analogue 112G/S induced unresponsiveness in the T cells to subsequent culture with the wild type peptide.

CONCLUSIONS

The data presented here suggest that using reagents such as altered peptides may represent a strategy to prevent the activation of T cells with indirect alloreactivity and allograft rejection in vivo.

Human T cells with a type-2 cytokine profile are resistant to apoptosis induced by primary activation: consequences for immunopathogenesis

The mechanisms leading to a relative dominance of T cells producing type 2 cytokines in certain human immune disorders are still unclear. We investigated the relative susceptibility to apoptosis induced by primary in vitro activation of human type 1 (producing interferon-gamma (IFN-gamma)) or type 2 (producing IL-4) T cells. Peripheral blood lymphocytes were isolated from patients with immune disorders characterized by expansion of type 2 cells (four with AIDS and hyper-IgE/hypereosinophilia, one with Churg-Strauss syndrome, and one with idiopathic hypereosinophilic syndrome) or from individuals with normal cytokine balances. Cells were stimulated for 16 h with ionomycin and phorbol ester, and apoptosis of cytokine-producing cells was assessed by flow cytometry. T cells with a type-2 cytokine profile, i.e. producing IL-4 alone, were significantly more resistant to activation-induced apoptosis than those producing IFN-gamma alone. This was observed in AIDS patients, whose type 2 cells were mostly CD8+, as well as in the patients with Churg-Strauss and with hypereosinophilic syndrome. CD4+ and CD8+ IL-4-producing cells were equally resistant to apoptosis. Lower susceptibility to apoptosis of type-2 T cells was also observed in subjects with normal cytokine balances. Bcl-2 expression was high in type-2 cells and in viable type-1 cells, whereas it was low in apoptotic type-1 cells. Resistance to activation-induced apoptosis may explain the expansion of cells producing type-2 cytokines in certain immune disorders.

Hypervariable region 1 variants act as TCR antagonists for hepatitis C virus-specific CD4+ T cells

In various human viral infections, the appearance of mutated epitopes displaying TCR antagonistic activity has been correlated with the severity and persistence of infection. In hepatitis C virus (HCV) infection, where the virus persistence has been associated with the rapid and substantial Ag modifications occurring during replication, TCR antagonism has been evidenced in CD8+ T cell responses. However, CD4+ T cell antagonism may be another important strategy by which HCV eludes a protective response, because sustained Th responses directed against several HCV Ags are associated with a self-limited course of infection. The data reported here represent the first evidence that variants of the hypervariable region (HVR1) of the putative Envelope 2 protein of HCV can act as powerful TCR antagonists for HVR1-specific CD4+ T cells isolated from HCV-infected individuals. Using classical antagonism assays, we observed strong inhibition of cellular proliferation and cytokine production when the agonist and the antagonist ligands were simultaneously presented by the same APCs. The presence in HVR1 of conserved residues, critical for binding to HLA-DR molecules, supports the function of HVR1 variants as TCR antagonists. In conclusion, our data evidence an antagonism phenomenon, which was achieved by naturally occurring class II-restricted T cell epitopes whose mechanism was addressed in terms of the antagonist capacity to inhibit agonist-mediated TCR down-regulation and early signal transduction.

Hypervariable Region 1 Variants Act as TCR Antagonists for Hepatitis C Virus-Specific CD4+ T Cells

In various human viral infections, the appearance of mutated epitopes displaying TCR antagonistic activity has been correlated with the severity and persistence of infection. In hepatitis C virus (HCV) infection, where the virus persistence has been associated with the rapid and substantial Ag modifications occurring during replication, TCR antagonism has been evidenced in CD8+ T cell responses. However, CD4+ T cell antagonism may be another important strategy by which HCV eludes a protective response, because sustained Th responses directed against several HCV Ags are associated with a self-limited course of infection. The data reported here represent the first evidence that variants of the hypervariable region (HVR1) of the putative Envelope 2 protein of HCV can act as powerful TCR antagonists for HVR1-specific CD4+ T cells isolated from HCV-infected individuals. Using classical antagonism assays, we observed strong inhibition of cellular proliferation and cytokine production when the agonist and the antagonist ligands were simultaneously presented by the same APCs. The presence in HVR1 of conserved residues, critical for binding to HLA-DR molecules, supports the function of HVR1 variants as TCR antagonists. In conclusion, our data evidence an antagonism phenomenon, which was achieved by naturally occurring class II-restricted T cell epitopes whose mechanism was addressed in terms of the antagonist capacity to inhibit agonist-mediated TCR down-regulation and early signal transduction.

Lymphocyte Activation Gene-3 (LAG-3) Expression and IFN-γ Production Are Variably Coregulated in Different Human T Lymphocyte Subpopulations

We evaluated the relationship between cytokine profile and the expression of the lymphocyte activation gene-3 (LAG-3) in both T cell clones and polyclonal T cell lines; LAG-3 is a CD4-like protein whose expression is reportedly restricted to Th1/0 cells and dependent upon IFN-γ. We found that, while LAG-3 was expressed only by CD4+ T cell clones producing IFN-γ, most CD8+ clones producing IL-4 but not IFN-γ (i.e., with a T cytotoxic-2-like profile) were LAG-3+. The intensity of LAG-3 expression by CD8+ clones correlated with the amount of released IFN-γ, suggesting that this cytokine is not required for expression but rather for the up-regulation of LAG-3. Flow cytometric analyses of polyclonal T cell lines confirmed that LAG-3 could be expressed by both CD4+ and CD8+ cells that did not contain cytoplasmic IFN-γ. In these cell lines, large proportions of CD4+ and CD8+ cells coexpressed LAG-3 and CD30, a putative marker of Th2-like cells. Overall, our data do not support the earlier suggestion that LAG-3 and CD30 are selective markers of T cells with type-1 and type-2 cytokine profiles, respectively.

Lymphocyte activation gene-3 (LAG-3) expression and IFN-gamma production are variably coregulated in different human T lymphocyte subpopulations

We evaluated the relationship between cytokine profile and the expression of the lymphocyte activation gene-3 (LAG-3) in both T cell clones and polyclonal T cell lines; LAG-3 is a CD4-like protein whose expression is reportedly restricted to Th1/0 cells and dependent upon IFN-gamma. We found that, while LAG-3 was expressed only by CD4+ T cell clones producing IFN-gamma, most CD8+ clones producing IL-4 but not IFN-gamma (i.e., with a T cytotoxic-2-like profile) were LAG-3+. The intensity of LAG-3 expression by CD8+ clones correlated with the amount of released IFN-gamma, suggesting that this cytokine is not required for expression but rather for the up-regulation of LAG-3. Flow cytometric analyses of polyclonal T cell lines confirmed that LAG-3 could be expressed by both CD4+ and CD8+ cells that did not contain cytoplasmic IFN-gamma. In these cell lines, large proportions of CD4+ and CD8+ cells coexpressed LAG-3 and CD30, a putative marker of Th2-like cells. Overall, our data do not support the earlier suggestion that LAG-3 and CD30 are selective markers of T cells with type-1 and type-2 cytokine profiles, respectively.

Death of bystander cells by a novel pathway involving early mitochondrial damage in human immunodeficiency virus-related lymphadenopathy

Destruction of immune cells in peripheral lymphoid tissues plays presumably a pivotal role in acquired immune deficiency syndrome pathogenesis. We found that cell suspensions obtained from lymph nodes of eight human immunodeficiency virus (HIV)-infected individuals contained variable proportions (2.1% to 18.3%, median 11.2%) of dead lymphocytes permeable to supravital dyes, represented by CD4+, CD8+, and B cells. The frequency of dead cells correlated directly (R = 0.847) with the amount of HIV provirus in the cell populations, and HIV provirus was enriched in the dead cell fractions. Similar proportions of dead cells were observed in cell suspensions from lymphadenopathic lymph nodes of HIV- donors, but not from small resting HIV- lymph nodes. Electron microscopic and flow cytometric analyses revealed that most dead cells from HIV+ lymph nodes lacked internucleosomal DNA fragmentation but displayed combined features of apoptosis and necrosis, eg, chromatin condensation and mitochondrial swelling. Cells with similar morphology were readily identified in lymph node tissue sections, and marked mitochondrial swelling could be occasionally observed in cells with otherwise normal morphology. Our findings have two major implications. One is that the in vivo cell death in HIV-infected lymph nodes occurs predominantly through a novel pathway, related to but distinct from classical apoptosis and characterised by early and severe mitochondrial damage. The second implication is that HIV-related lymphadenopathy is accompanied in vivo by massive destruction of uninfected lymph node cells. Comparable levels of cell death were observed in other inflammatory lymphadenopathies not related to HIV; however, the uniquely endless and generalized nature of HIV lymphadenopathy might render this "inflammatory" cell destruction a powerful pathogenetic mechanism, accounting for the progressive disruption and depletion of lymphoid tissues seen in HIV infection.

Comparison of the Vbeta repertoire in peripheral blood and in lymph nodes of HIV-infected subjects reveals skewed usage predominantly in CD8+ T cells

Perturbations of the repertoire of variable-beta (Vbeta) regions of the T cell receptor have been observed in patients infected by HIV and have been attributed to stimulation by viral antigens or superantigens. We further sought for traces of HIV-induced perturbations by comparing Vbeta repertoire in peripheral blood and in lymphoid tissues of six infected patients. Vbeta expression was studied with a panel of 17 anti-Vbeta antibodies covering about 50% of the entire repertoire. We observed major divergences between lymph nodes and peripheral blood in the expression of several Vbeta segments, and these differences were significantly more frequent in CD8+ than in CD4+ T cells (P = 0.0097). Vbeta2 was perturbed in CD8 cells from all but one patient. One HIV-negative subject with localized reactive lymphadenopathy of unknown etiology had four perturbed Vbeta segments, including Vbeta2, in CD8+ cells, while another uninfected subject with an unreactive lymph node architecture had no perturbations. Our findings suggest that stimulation by HIV or by other antigens determines divergences in the Vbeta repertoire between lymphoid tissues and peripheral blood predominantly in CD8+ T cells.

Measurement of apoptotic cells in peripheral blood

The measurement of apoptosis in peripheral blood might represent a useful tool in acquired immunodeficiency syndrome (AIDS) and cancer research. Among the many assays that are currently used to identify apoptotic leukocytes, flow cytometric methods are the most valuable in terms of rapidity, simplicity, and level of analytical detail. Some flow cytometric assays may also offer the additional advantage of detecting the earliest phases of apoptosis, which is paramount importance for measuring apoptotic cells in vivo before they are destroyed by phagocytes.

TCL1 oncogene activation in preleukemic T cells from a case of ataxia-telangiectasia

The TCL1 oncogene on human chromosome 14q32.1 is involved in chromosome translocations [t(14;14)(q11;q32.1) and t(7;14)(q35;q32.1)] and inversions [inv14(q11;q32.1)] with TCR alpha/beta loci in T-cell leukemias, such as T-prolymphocytic (T-PLL). It is also involved in T-acute and -chronic leukemias arising in cases of ataxia-telangiectasia (AT), an immunodeficiency syndrome. Similar chromosomal rearrangements occur also in the clonally expanded T cells in AT patients before the appearance of the overt leukemia. We have analyzed the expression of TCL1 mRNA and protein in peripheral blood lymphocytes (PBLs) from four AT cases and from healthy controls. We found that the TCL1 gene was overexpressed in the PBLs of an AT patient with a large clonal T-cell population exhibiting the t(14;14) translocation but not in the lymphocytes of the other cases. Fluorescence in situ hybridization of the TCL1 genomic locus to lymphocyte metaphases from the AT patient with the T-cell clonal expansion showed that the breakpoint of the t(14;14) translocation lies within the TCL1 locus and is accompanied by an inverted duplication of the distal part of chromosome 14. These data indicate that TCL1 is activated in preleukemic clonal cells as a consequence of chromosome translocation involving sequences from the TCR locus at 14q11. Deregulation of TCL1 is the first event in the initiation of malignancy in these types of leukemias and represents a potential tool for clinical evaluation.

Frequency of provirus-bearing CD4+ cells in HIV type 1 infection correlates with extent of in vitro apoptosis of CD8+ but not of CD4+ cells

Lymphocytes from HIV-1-infected subjects undergo massive apoptosis when cultured in vitro, and this phenomenon might reflect pathogenetic mechanisms leading to immune dysfunction in vivo. However, (1) lymphocyte death is not restricted to CD4+ cells but seems to involve predominantly CD8+ cells, and (2) the same phenomenon occurs in other viral infections. Furthermore, it is not known whether a relationship exists between the HIV-1 burden and this type of cell death. In this work we sought to determine whether the HIV-1 provirus load correlates with the propensity to apoptosis of CD4+ and CD8+ cells. We studied 10 HIV-1-infected patients with CD4+ cell counts above 500/mm3 and free of concomitant infections. We correlated the frequency of HIV-1-infected CD4+ cells with the extent of culture-induced apoptosis as well as with the phenotype of the apoptotic lymphocytes. We found that the magnitude of apoptosis correlated with the frequency of HIV-1-infected CD4+ cells (p = 0.0007), and that increasing viral load and apoptosis were associated with a shift to the selective death of CD8+ cells. Our data support the view that, in addition to CD4+ cell killing, another immunopathogenic effect of HIV might be that of priming CD8+ cells to apoptosis. In vivo, this could eventually lead to the exhaustion of the cytotoxic T cell compartment.

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).

Activated and "memory" phenotype of circulating T lymphocytes in intrauterine life

We examined the expression of T cell markers in the peripheral blood of five immunologically normal human fetuses at 18-20 weeks of gestational age. The distribution of T cells expressing CD1, CD3, CD4, CD8, CD56, and the alpha/beta and gamma/delta receptors for antigen was comparable to that of newborns and normal adults, except for the absence of gamma/delta cells expressing the delta TCS-1 epitope. The V beta repertoire, as evaluated by two-color flow cytometry using mAbs to specific V beta families, was also comparable to that of adult samples. A significant fraction (8.9 to 16.4%) of fetal CD3+ T cells expressed the alpha chain of IL-2R (CD25) in the absence of HLA-DR; this suggests that antigenic stimuli trigger, during intrauterine life, an unusual pathway of T cell activation. Consistent with this, 7 to 27% of fetal T cells were found to express the CD45R0 marker of "memory" cells.

Detection and characterization of apoptotic peripheral blood lymphocytes in human immunodeficiency virus infection and cancer chemotherapy by a novel flow immunocytometric method

We have developed a quantitative and sensitive flow cytometric method for the detection of human apoptotic lymphocytes that, unlike previously described assays, allows their identification in mixed populations of peripheral blood leukocytes as well as their immunophenotyping. Apoptotic lymphocytes are identified on the basis of peculiar light scatter changes, reflecting their smaller size and their modified nucleus/cytoplasm organization, and of the decreased expression of surface CD45 molecules. Based on these criteria, apoptotic lymphocytes generated by exposure to ionizing radiation can be easily distinguished from viable cells and from necrotic lymphocytes generated by treatment with antibody and complement. Using this assay, we reappraised the phenomenon of the in vitro apoptosis of lymphocytes from patients with human immunodeficiency virus (HIV) infection. Lymphocytes from HIV patients, unlike those from normal HIV-negative subjects, undergo apoptosis upon simple in vitro culture. We found that the percentages of lymphocytes undergoing apoptosis were significantly higher in patients with low CD4 cell counts (< 400/microL) than in patients at earlier stages (> 400 CD4 cells/microL). However, phenotypic analysis disclosed that apoptotic lymphocytes generated in these cultures were mostly CD8+ T cells and CD19+ B cells. Thus, in contrast to what has been previously suggested, the phenomenon of in vitro lymphocyte apoptosis might not be pathogenetically related to the depletion of CD4+ T cells in acquired immunodeficiency syndrome. Nevertheless, it might represent an useful marker of disease progression. Our assay allows the analysis of unfractionated peripheral blood leukocytes and thus the identification of apoptotic lymphocytes circulating in vivo. Apoptotic lymphocytes could indeed be detected in the circulation of a patient with cancer shortly after high-dose cytotoxic chemotherapy. By contrast, no apoptotic lymphocytes could be detected in vivo in patients with early or advanced HIV infection.

T-lymphocyte reactivity to the recombinant mycobacterial 65- and 70-kDa heat shock proteins in multiple sclerosis

Owing to their conservation and immunogenicity, heat shock proteins (hsps) represent a class of potential autoantigens. Moreover, they could be targets for gamma delta T lymphocytes, which are prominent in various immune disorders. We studied the T cell proliferative primary responses to recombinant M. bovis 65 kDa hsp (hsp65) and M. tuberculosis 70 kDa hsp (hsp70) in 31 patients with multiple sclerosis (MS), 19 patients with other neurological diseases (OND) and 19 healthy individuals. Positive responses to hsp70, but not to hsp65 were significantly more frequent in patients with MS than in patients with OND or in healthy individuals. In order to verify and refine these results and to characterize the hsp reactive T lymphocytes, we screened 147 PPD-specific long-term T cell lines (76 from 10 patients with MS and 71 from 12 healthy donors) for their proliferative response to hsp65 and hsp70. hsp70-reactive T lines were significantly more common in patients with MS than in healthy controls. The number of T lines responding to hsp65 increased in the MS group only slightly. In 19 T lymphocyte lines from patients with MS and healthy donors, a cytofluorometric analysis was performed with special attention paid to distinct T cell receptor gamma delta determinants. With one exception, in each line the population of gamma delta T cells remained a minority. We conclude that an increased T cell response to mycobacterial hsp70 may be present in patients with multiple sclerosis.

Absence of antibodies to human herpesvirus-6 in patients with slowly-progressive human immunodeficiency virus type 1 infection

To evaluate a possible role for Human Herpesvirus-type 6 (HHV-6) coinfection as a co-factor in the progression of HIV-1 disease, we investigated the prevalence of seropositivity for HHV-6 in a cohort of HIV-1 infected patients. These patients were retrospectively divided into two groups according to the decline of CD4+ T cells during the follow up: 11 were classified as rapid decliners (less than 400 CD4+/cmm within 1 year), and 38 as slow decliners (greater than 400 CD4+/cmm after at least 4 years' follow up). HHV-6 antibodies were detected by a commercial immunofluorescence assay and by a Western blotting assay developed in our laboratory. Our results show that Western blot appears to provide results satisfactorily free of false positivities. We found that the frequency of HHV-6 seropositivity was significantly lower in the group of slow decliners, compared both to rapid decliners and to the general population. These data suggest a role for HHV-6 co-infection in the progression of HIV-1 disease.

Relative increase of T cells expressing the gamma/delta rather than the alpha/beta receptor in ataxia-telangiectasia

In ataxia-telangiectasia, B-cell and T-cell deficiencies are thought to be due to a defect of rearrangements of immunoglobulin and T-cell receptor genes. T cells recognize antigens through two types of CD3-associated receptors: alpha/beta chains on mature cells and gamma/delta chains mostly on immature cells. We studied 10 patients with ataxia-telangiectasia and found that most had a relative increase of circulating T cells bearing gamma/delta receptors rather than alpha/beta receptors, as compared with normal subjects (P less than 0.001). Patients with other immune deficits, including eight with common variable immunodeficiency, one with Wiskott-Aldrich syndrome, two with hyperimmunoglobulinemia E syndrome, and one with severe combined immunodeficiency, had normal ratios of gamma/delta-bearing to alpha/beta-bearing cells. A marked predominance of gamma/delta-bearing T cells was found in a patient with a primary T-cell defect. The relative increase in gamma/delta-bearing T cells in the patients with ataxia-telangiectasia was largely accounted for by cells that reacted with the monoclonal antibody BB3, an apparently distinct subset of T cells that selectively express the C gamma 1 gene product of the T-cell receptor. Although they had normal ratios of gamma/delta-bearing to alpha/beta-bearing T cells, the patients with common variable immunodeficiency had a significant increase (P = 0.01) in the number of T cells expressing C gamma 2 that reacted with the monoclonal antibody delta-TCS-1. We conclude that the increased ratio of gamma/delta-bearing to alpha/beta-bearing T cells in ataxia-telangiectasia may reflect both a recombinational defect that interferes with T-cell and B-cell gene rearrangements and an inability to repair damage to the DNA.

Establishment of a new Epstein-Barr virus-immortalized cell line from chronic lymphocytic leukemia with trisomy of chromosome 12 that produces monoclonal IgM against a sheep RBC antigen

Leukemia cells from a patient with chronic lymphocytic leukemia (CLL) were found to bind sheep RBC (SRBC) through their monoclonal surface IgM. A lymphoblastoid cell line was obtained by immortalization of leukemic cells with Epstein-Barr virus (EBV). Cultured leukemic cells were found to have a supernumerary chromosome 12, an abnormality typical of CLL of the B cell type. To our knowledge, this is the first EBV-immortalized cell line from B-CLL cells of known SRBC specificity and the third reported CLL cell line carrying trisomy of chromosome 12.

IgG anti-IgE in circulating immune complexes in the hyper-IgE syndrome

We fractionated, by gel chromatography, sera with high IgE content from atopic subjects and five cases with the hyper-IgE syndrome, and measured the presence of IgE in high molecular weight (HMW) fractions. Two out of four asthmatics and four out of five hyper-IgE had HMW IgE. The same serum fractions gave positive results for conglutinin binding IgG (all six) and IgA (three cases) as well as C1q binding complexes (five cases). IgG auto-antibodies to IgE were also detected together with IgE in HMW fractions. Anti-F(ab)'2 activity was present in five cases (one of them negative for IgG anti-IgE). Our data indicate that complexes made of IgE and IgG anti-IgE are present mainly in patients with chronic allergic symptoms and most frequent in cases of hyper-IgE syndrome.

Deficiency of natural killer activity, but not of natural killer binding, in patients with lymphoadenopathy syndrome positive for antibodies to HTLV-III

Blood lymphocytes (BL) of eleven patients with lymphoadenopathy syndrome (LAS) were studied for natural killer (NK) activity against the K562 cell line (using both the standard 51Cr release assay and the single-cell cytotoxicity assay on poly-L-lysine-coated coverslips) and for surface phenotype (employing OKT4, OKT8 and Leu7 monoclonal antibodies). A significant reduction in NK activity and in NK active cells was detected, while the percentage of target binding cells was not affected. Furthermore, the OKT4/OKT8 ratio was found to be inverted, and the Leu7+ subpopulation expanded. The patients had high titers of anti-HTLV-III antibodies. This study indicates that defective NK activity in LAS is secondary to an abnormality in the lytic event itself and not in target binding.

Hypogammaglobulinemia with hyper-IgM, severe T-cell defect, and abnormal recirculation of OKT4 lymphocytes in a girl with chronic lymphadenopathy

We describe here one 8-year-old girl with an unusual form of immunodeficiency, characterized by hypogammaglobulinemia with hyper-IgM, severe T-cell defect, and chronic lymphadenopathy. Patient's B cells failed to produce IgG or IgA in vitro following stimulation with either pokeweed mitogen or Epstein-Barr virus, suggesting an intrinsic B-cell defect. Abnormal T-cell function was demonstrated by impaired in vivo delayed type hypersensitivity, reduction of mitogen-induced proliferation and interleukin 2 production, reduction of interferon-gamma production, and marked decrease of circulating OKT4+ cells. The latter cells were found in normal proportion in the patient's lymph node tissue. This finding suggests that the decrease of OKT4+ cells in peripheral blood was due to the abnormal recirculation of these cells. The identity of this syndrome with the infantile form of the acquired immunodeficiency syndrome was apparently ruled out by the failure to demonstrate HTLV-III-related sequences in patient's lymphocytes or virus-specific serum antibodies.

Demonstration of antibodies to human T-lymphotropic retrovirus type III in lymphoadenopathy syndrome patients and in individuals at risk for acquired immune deficiency syndrome (AIDS) in Italy

An epidemiologic survey of the distribution of lymphoadenopathy syndrome in six Italian cities and its correlation with human T-lymphotropic retrovirus III (HTLV-III) is reported. Serum samples of nine patients with acquired immune deficiency syndrome (AIDS) were tested, 180 from patients with lymphoadenopathy and 349 from individuals belonging to groups such as homosexuals, drug addicts, hemophiliacs, and polytransfused considered at increased risk for AIDS. Prevalence of HTLV-III antibodies was 78% in AIDS patients and 61% in 180 patients with lymphoadenopathy syndrome (variation among drug abusers by city from 51% in Cagliari to 87% in Rome). The percentage of positive sera in individuals at risk for AIDS or lymphoadenopathy ranged from 0% in polytransfused to 8.5% in homosexuals, 14% in drug addicts, and 19.5% in hemophiliacs. No positive sera were found among 660 healthy individuals including relatives of patients with AIDS or lymphoadenopathy or in 342 patients suffering from immunologic or infectious diseases. These results strongly suggest that HTLV-III is the causative agent of AIDS and lymphoadenopathy. Since none of the healthy subjects were positive while a substantial percentage of people at risk for AIDS showed antibodies to HTLV-III, it may be presumed that this infection is also prevalent in the Italian population group in which AIDS and lymphoadenopathy are most likely to develop.

Phenotypically immature IgG-bearing B cells in patients with hypogammaglobulinemia

We investigated the prevalence of phenotypically immature IgG B cells (i.e., coexpressing surface IgG and IgM) in the peripheral blood of 12 patients with hypogammaglobulinemia and in normal individuals. Patients had ataxia-telangiectasia (N = 1), hyper-IgM combined immunodeficiency (N = 1), or common variable immunodeficiency (CVI). IgG/IgM-positive B cells were evaluated by two-color immunofluorescence using fluorescein- or rhodamine-conjugated goat antiserum; to minimize artifacts due to in vivo cytophilic binding of autologous IgG, cell-bound cytophilic Ig were eluted at pH 4 and Fc receptors were blocked by heat-aggregated rabbit IgG before fluorescent staining. All patients, except two with late-onset CVI, had markedly increased proportions of double-stained IgG B cells (56 to 100% of IgG-bearing B cells) in comparison with normal individuals (11 to 33%).

Epidemiological aspects of HTLV-III infection in Italy

An epidemiological survey on the presence of serum antibodies to human T lymphotropic retrovirus III (HTLV-III) is reported. The study was carried out on people living in large as well as small cities in different Italian regions. Serum samples of 21 patients with AIDS, 402 with ARCS, and 920 from individuals at risk for these diseases were analyzed. The percentage of positive sera varied from 81% in AIDS, to 100% -33.3% in ARC according to the different geographical areas and/or the various categories of people with ARC. The percentage of positive sera in individuals at risk for AIDS or ARC varied from 11.9% in homosexuals, to 21% in drug abusers and 23.1% in haemophiliacs. No positive sera were observed among 660 normal individuals, relatives of patients with AIDS or ARC and in 114 patients suffering from immunological or infectious disease and among people at risk living in small cities. Sera were also negative in patients with classical Kaposi's sarcoma or T-cell chronic lymphocytic leukemia. Since none of the 660 unselected normal adults were positive while a significant percentage of people at risk for AIDS showed antibodies to HTLV-III, we may presume that this infection is prevalent in the Italian categories in which AIDS and ARC are most likely to develop.

Natural killer cells in intravenous drug abusers with lymphadenopathy syndrome

We have investigated 25 intravenous drug abusers with the clinical and laboratory features of lymphadenopathy syndrome (LAS) and 10 AIDS patients for the expression of NK activity. LAS and AIDS patients had low NK cytotoxicity compared to normal donors. The defective NK cytotoxicity was analysed in the eight LAS subjects with most marked depression. NK effectors were identified by morphology (large granular lymphocytes, LGL) and monoclonal antibody-defined surface markers (B73.1, N901, HNK1). LAS patients had normal percentages of LGL and B73.1+ and N901+ cells. with the exception of two subjects with very low frequency of B73.1+ and N901+ cells. The percentage of HNK1+ cells was increased in LAS, probably because of the reactivity of this reagent with a subset of conventional OKT8+ cells, relatively augmented in LAS subjects. Depletion of monocytes did not enhance NK activity consistently. LAS patients had a normal frequency of cells capable of binding K562. In-vitro exposure to interferon beta (natural) or gamma (recombinant) augmented the defective NK activity of LAS subjects. Thus, patients with LAS have defective NK activity that cannot be accounted for by a low frequency of the relevant effector cells or by monocytic suppressors. These observations suggest a functional defect of NK cells at one or more of the post-binding steps required for the completion of killing.

IgM and IgG antibodies to human T cell lymphotropic retrovirus (HTLV-III) in lymphadenopathy syndrome and subjects at risk for AIDS in Italy

A study was performed to assess the prevalence of specific antibodies to human T cell lymphotropic retrovirus (HTLV-III) in patients with lymphadenopathy syndrome, patients with the acquired immune deficiency syndrome (AIDS), and those at risk of AIDS. Serum samples were obtained from these groups and from healthy controls in selected cities in Italy, and antibodies to HTLV-III were measured by immunofluorescence assay and, in a few patients, by Western blotting. In addition, IgM antibody values were measured in 82 of those positive for HTLV-III. Altogether, 235 out of 320 patients with lymphadenopathy syndrome had antibodies to HTLV-III, the proportions being highest in haemophiliacs, homosexuals, and drug addicts from Rome; 11 out of 12 patients with AIDS had antibodies; 78 out of 439 subjects at risk for AIDS had antibodies; and six out of 30 patients with lymphadenopathy syndrome and positive for HTLV-III antibodies and nine of 52 patients at risk of AIDS had a detectable titre of IgM. HTLV-III is widespread in groups at risk of AIDS in Italy, and antibodies to HTLV-III are highly prevalent in patients with lymphadenopathy syndrome. A higher proportion of drug abusers were positive for antibodies than in previous studies. HTLV-III "infection" would appear to be spread mainly in compromised hosts, as none of the controls were positive for antibodies.