Platelet-activating factor acetylhydrolase is a biomarker of severe anaphylaxis in children

BACKGROUND

There is limited ability to predict the severity of allergic reactions in children. Data derived predominantly from adults have implicated the platelet-activating factor pathway as a potential contributor to severe anaphylaxis. In this study, we sought to prospectively assess involvement of key components of the platelet-activating factor pathway in pediatric patients with anaphylaxis.

METHODS

Forty-six pediatric patients (<18 years) presenting with acute anaphylaxis were assessed. Anaphylaxis severity was graded and serum anaphylaxis markers were measured acutely and in 36 children who returned for follow-up >4 weeks after their acute presentation. These markers were compared with pediatric laboratory reference sera.

RESULTS

Severe anaphylaxis was experienced by 12/46 (26%) and mild-moderate anaphylaxis in 34/46 (74%) children. Platelet-activating factor acetylhydrolase (PAF-AH) activity was inversely associated with severe anaphylaxis: 9/12 children with severe anaphylaxis had reduced PAF-AH activity as compared with 14/34 with mild-moderate anaphylaxis (p < .05). Furthermore, 3/3 children who required intensive care had markedly reduced mean PAF-AH (nmol/ml/min) (13.73, 95%CI: 7.42-20.03) versus 20/23 who required ward/emergency department care (17.81, 95%CI: 16.80-18.83; p < .05). In children with anaphylaxis, PAF-AH during acute anaphylaxis was unchanged relative to the child's basal levels (mean, 17.26, 95%CI: 16.10-18.42 vs 17.50, 95%CI: 16.21-18.78, p = .63) and was lower than healthy pediatric controls (mean 19.21; 95%CI:18.21-20.21; p < .05).

CONCLUSION

Decreased serum PAF-AH activity is a biomarker of severe anaphylaxis. Levels of this enzyme do not change from basal levels during acute anaphylaxis. Our results show that PAF-AH is a biomarker of anaphylaxis severity in children. This key regulatory enzyme may modulate susceptibility to severe anaphylaxis.

Progressive decline of T and B cell numbers and function in a patient with CDC42 deficiency

Single allele mutations in the Cell Division Control protein 42 homolog (CDC42) gene were recently shown to cause Takenouchi-Kosaki syndrome with diverse manifestations. These include persistent mild thrombocytopenia with large platelet size, severe developmental delay, growth retardation, facial dysmorphism, and other neurodevelopmental and hematological anomalies. CDC42 deficiency might also cause myelofibrosis, myeloproliferation, and severe autoinflammation. CDC42 closely interacts with the Wiskott-Aldrich Syndrome Protein, but little is still known about the immune abnormalities associated with CDC42 deficiency. Detailed immune evaluations were performed in a patient diagnosed with a CDC42 Tyr64Cys mutation. The 19-year-old female suffered from recurrent pneumonia, otitis media, and bacteremia, which resolved at 10 years of age, concordant with the initiation of amoxicillin prophylaxis. In addition, the patient had frequent viral upper respiratory tract infections, which resolved without need for medical interventions. Immune evaluations demonstrated decreased immunoglobulin levels, inability to maintain antibody responses, progressive decline in the number of CD19+ B cells, and decreased switched memory B cells. There was also a decrease in CD4+ and CD8+ T cells, markedly reduced naïve T cells, and intermittent depressed proliferation of T cells to stimulation. Natural killer cells' number and functions were normal. However, no opportunistic infections were observed, nor was there evidence for autoinflammation. CDC42 deficiency might also be associated with decline in T and B cell function. Therefore, immunity in patients with CDC42 defects should be closely monitored, particularly among those with frequent infections or systemic autoinflammation.

Partial Purine Nucleoside Phosphorylase Deficiency Helps Determine Minimal Activity Required for Immune and Neurological Development

Introduction: Complete or near complete absence of the purine nucleoside phosphorylase (PNP) enzyme causes a profound T cell immunodeficiency and neurological abnormalities that are often lethal in infancy and early childhood. We hypothesized that patients with partial PNP deficiency, characterized by a late and mild phenotype due to residual PNP enzyme, would provide important information about the minimal PNP activity needed for normal development. Methods: Three siblings with a homozygous PNP gene mutation (c.769C>G, p.His257Asp) resulting in partial PNP deficiency were investigated. PNP activity was semi-quantitively assayed by the conversion of [14C]inosine in hemolysates, mononuclear cells, and lymphoblastoid B cells. PNP protein expression was determined by Western Blotting in lymphoblastoid B cells. DNA repair was quantified by measuring viability of lymphoblastoid B cells following ionizing irradiation. Results: A 21-year-old female was referred for recurrent sino-pulmonary infections while her older male siblings, aged 25- and 28- years, did not suffer from significant infections. Two of the siblings had moderately reduced numbers of T, B, and NK cells, while the other had near normal lymphocyte subset numbers. T cell proliferations were normal in the two siblings tested. Hypogammaglobulinemia was noted in two siblings, including one that required immunoglobulin replacement. All siblings had typical (normal) neurological development. PNP activity in various cells from two patients were 8-11% of the normal level. All siblings had normal blood uric acid and increased PNP substrates in the urine. PNP protein expression in cells from the two patients examined was similar to that observed in cells from healthy controls. The survival of lymphoblastoid B cells from 2 partial PNP-deficient patients after irradiation was similar to that of PNP-proficient cells and markedly higher than the survival of cells from a patient with absent PNP activity or a patient with ataxia telangiectasia. Conclusions: Patients with partial PNP deficiency can present in the third decade of life with mild-moderate immune abnormalities and typical development. Near-normal immunity might be achieved with relatively low PNP activity.

Comparison of elapegademase and pegademase in ADA-deficient patients and mice

The absence of adenosine deaminase (ADA) causes severe combined immune deficiency (SCID), which has been treated with PEGylated bovine-extracted ADA (ADAGEN). ADAGEN was recently replaced by a PEGylated recombinant bovine ADA, expressed in Escherichia coli (elapegademase, ELA-ADA). Limited information on ELA-ADA is available.  ADA enzymatic activity of ELA-ADA and ADAGEN was assessed in vitro at diverse dilutions. ADA activity and immune reconstitution in an ADA-SCID patient treated with ELA-ADA were compared with age-matched patients previously treated with ADAGEN. ADA activity and thymus reconstitution were evaluated in ADA-deficient mice following ELA-ADA or ADAGEN administered from 7 days postpartum. In vitro, ADA activity of ELA-ADA and ADAGEN were similar at all dilutions. In an ADA-SCID patient, ELA-ADA treatment led to a marked increase in trough plasma ADA activity, which was 20% higher than in a patient previously treated with ADAGEN. A marked increase in T cell numbers and generation of naive T cells was evident following 3 months of ELA-ADA treatment, while T cell numbers increased following 4 months in 3 patients previously treated with ADAGEN. T cell proliferations stimulation normalized and thymus shadow became evident following ELA-ADA treatment. ADA activity was significantly increased in the blood of ADA-deficient mice following ELA-ADA compared to ADAGEN, while both treatments improved the mice weights, the weight, number of cells in their thymus and thymocyte subpopulations. ELA-ADA has similar in- vitro and possibly better in-vivo activity than ADAGEN. Future studies will determine whether ELA-ADA results in improved long-term immune reconstitution.

A Fibroblast Growth Factor 21-Pregnane X Receptor Pathway Downregulates Hepatic CYP3A4 in Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) alters drug response. We previously reported that NAFLD is associated with reduced in vivo CYP3A drug-metabolism activity and hepatic CYP3A4 expression in humans as well as mouse and human hepatoma models of the disease. Here, we investigated the role of the lipid- and glucose-modulating hormone fibroblast growth factor 21 (FGF21) in the molecular mechanism regulating CYP3A4 expression in NAFLD. In human subjects, mouse and cellular NAFLD models with lower CYP3A4 expression, circulating FGF21, or hepatic FGF21 mRNA levels were elevated. Administration of recombinant FGF21 or transient hepatic overexpression of FGF21 resulted in reduced liver CYP3A4 luciferase reporter activity in mice and decreased CYP3A4 mRNA expression and activity in cultured Huh7 hepatoma cells. Blocking canonical FGF21 signaling by pharmacological inhibition of MEK1 kinase in Huh7 cells caused de-repression of CYP3A4 mRNA expression with FGF21 treatment. Mice with high-fat diet-induced simple hepatic steatosis and lipid-loaded Huh7 cells had reduced nuclear localization of the pregnane X receptor (PXR), a key transcriptional regulator of CYP3A4 Furthermore, decreased nuclear PXR was observed in mouse liver and Huh7 cells after FGF21 treatment or FGF21 overexpression. Decreased PXR binding to the CYP3A4 proximal promoter was found in FGF21-treated Huh7 cells. An FGF21-PXR signaling pathway may be involved in decreased hepatic CYP3A4 metabolic activity in NAFLD.

T lymphocytes possess the machinery for 5-HT synthesis, storage, degradation and release

AIM

Although activated T lymphocytes express tryptophan hydroxylase 1 and produce 5-HT, the metabolic fate and cellular handling of this 5-HT is unclear. Here, we investigated key proteins in T cells linked to 5-HT metabolism and storage and compare differences in 5-HT synthesis and metabolism between T-cell subsets.

METHODS

We cultured human Jurkat T cells and mouse splenic CD3(+) , CD4(+) and CD8(+) T cells with or without T-cell activators (phorbol ester/ionomycin, concavalin A or plate-bound anti-CD3 antibody). Subsequently, we measured mRNA and/or protein for monoamine oxidase A and B, vesicular monoamine transporter 1 and 2, N-acetyl transferase and tryptophan hydroxylase 1. In addition, we measured the release of exogenously loaded [(3) H]5-HT and endogenously synthesized 5-HT from CD4(+) and CD8(+) T-cell subsets.

RESULTS

Human and mouse T cells selectively express monoamine oxidase A. Following T-cell activation, mRNA levels of MAO-A increase robustly in parallel with tryptophan hydroxylase 1. Concomitant with these changes, T cells increase the expression of the type 1 vesicular monoamine transporter. Raised intracellular [Ca(2+) ] rapidly releases preloaded [(3) H]5-HT from CD4(+) and CD8(+) T cells indicating that these cells have the capacity for the storage and regulated secretion of 5-HT. Notably, both the expression of tryptophan hydroxylase 1 and monoamine oxidase A, and 5-HT production are significantly greater in CD8(+) compared with CD4(+) T cells.

CONCLUSION

These data reveal coordinated changes in 5-HT production, metabolism and storage that may optimize 5-HT secretion from the CD8(+) T cell subset in response to activation stimuli.

Hepatic organic anion transporting polypeptide transporter and thyroid hormone receptor interplay determines cholesterol and glucose homeostasis

The role of organic anion transporting polypeptides (OATPs), particularly the members of OATP1B subfamily, in hepatocellular handling of endogenous and exogenous compounds is an important and emerging area of research. Using a mouse model lacking Slco1b2, the murine ortholog of the OATP1B subfamily, we have demonstrated previously that genetic ablation causes reduced hepatic clearance capacity for substrates. In this study, we focused on the physiological function of the hepatic OATP1B transporters. First, we studied the influence of the Oatp1b2 deletion on bile acid (BA) metabolism, showing that lack of the transporter results in a significantly reduced expression of Cyp7a1, the key enzyme of BA synthesis, resulting in elevated cholesterol levels after high dietary fat challenge. Furthermore, Slco1b2-/- mice exhibited delayed clearance after oral glucose challenge resulting from reduced hepatic glucose uptake. In addition to increased hepatic glycogen content, Slco1b2-/- mice exhibited reduced glucose output after pyruvate challenge. This is in accordance with reduced hepatic expression of phosphoenolpyruvate carboxykinase (PEPCK) in knockout mice. We show that this phenotype is due to the loss of liver-specific Oatp1b2-mediated hepatocellular thyroid hormone entry, which then leads to reduced transcriptional activation of target genes of hepatic thyroid hormone receptor (TR), including Cyp7a1 and Pepck but also Dio1 and Glut2. Importantly, we assessed human relevance using a cohort of archived human livers in which OATP1B1 expression was noted to be highly associated with TR target genes, especially for glucose facilitating transporter 2 (GLUT2). Furthermore, GLUT2 expression was significantly decreased in livers harboring a common genetic polymorphism in SLCO1B1.

CONCLUSION

Our findings reveal that OATP1B-mediated hepatic thyroid hormone entry is a key determinant of cholesterol and glucose homeostasis.

LGL leukemia and HTLV

Samples were obtained from 53 large granular lymphocytic leukemia (LGLL) patients and 10,000 volunteer blood donors (VBD). Sera were screened in an HTLV-1 enzyme immunoassay (EIA) and further analyzed in peptide-specific Western blots (WB). DNAs were analyzed by HTLV-1, -2, -3, and -4-specific PCR. Forty four percent of LGLL patients vs. 0.12 % of VBD had anti-HTLV antibodies via EIA (p < 0.001). WB and PCR revealed that four LGLL patients (7.5%) vs. one VBD patient (0.01%) were infected with HTLV-2 (p < 0.001), suggesting an HTLV-2 etiology in a minority of cases. No LGLL patient was positive for HTLV-1, -3, or -4, whereas only one EIA-positive VBD was positive for HTLV-1 and none for HTLV-3 or -4. The HTLV EIA-positive, PCR-negative LGLL patients' sera reacted to epitopes within HTLV p24 gag and gp21 env. Other then the PTLV/BLV viruses, human endogenous retroviral element HERV K10 was the only sequence homologous to these two HTLV peptides, raising the possibility of cross-reactivity. Although three LGLL patients (5.7%) vs. none of 110 VBD patients tested positive for antibodies to the homologous HERV K10 peptide (p = 0.03), the significance of the anti-HTLV seroreactivity observed in many LGLL patients remains unclear. Interestingly, out of 36 HTLV-1-positive control subjects, 3 (8%) (p = 0.014) were positive for antibodies to HERV K10; all three had myelopathy. Out of 64 HTLV-2-positive control subjects 16 (25%) (p = <0.001) were positive for HERV K10 antibodies, and 4 (6%) of these had myelopathy. Out of 22 subjects with either HTLV-1 or -2 myelopathy, 7 (31.8%) were positive for HERV K10 antibodies, and out of 72 HTLV-infected subjects without myelopathy, 12 (16.7%) were positive for anti-HERV K10 antibodies (p = 0.11). The prevalence of anti-HERV K10 antibodies in these populations and the clinical implications thereof need to be pursued further.

Attenuation of massive cytokine response to the staphylococcal enterotoxin B superantigen by the innate immunomodulatory protein lactoferrin

Staphylococcal enterotoxin B (SEB) is a pyrogenic exotoxin and a potent superantigen which causes massive T cell activation and cytokine secretion, leading to profound immunosuppression and morbidity. The inhibition of SEB-induced responses is thus considered a goal in the management of certain types of staphylococcal infections. Lactoferrin (LF) is a multi-functional glycoprotein with both bacteriostatic and bactericidal activities. In addition, LF is known to have potent immunomodulatory properties. Given the anti-microbial and anti-inflammatory properties of this protein, we hypothesized that LF can modulate T cell responses to SEB. Here, we report that bovine LF (bLF) was indeed able to attenuate SEB-induced proliferation, interleukin-2 production and CD25 expression by human leucocyte antigen (HLA)-DR4 transgenic mouse T cells. This inhibition was not due to bLF's iron-binding capacity, and could be mimicked by the bLF-derived peptide lactoferricin. Cytokine secretion by an engineered SEB-responsive human Jurkat T cell line and by peripheral blood mononuclear cells from healthy donors was also inhibited by bLF. These findings reveal a previously unrecognized property of LF in modulation of SEB-triggered immune activation and suggest a therapeutic potential for this naturally occurring protein during toxic shock syndrome.

Dendritic cell differentiation induced by a self-peptide derived from apolipoprotein E

Dendritic cells (DCs) are professional APCs and potent stimulators of naive T cells. Since DCs have the ability to immunize or tolerize T cells they are unique candidates for use in immunotherapy. Our laboratory has discovered that a naturally processed self-peptide from apolipoprotein E, Ep1.B, induces DC-like morphology and surface marker expression in a murine monocytic cell line (PU5-1.8), human monocytic cell line (U937), murine splenocytes, and human peripheral blood monocytes. Microscopy and flow cytometric analysis revealed that Ep1.B-treated cells display decreased adherence to plastic and increased aggregation, dendritic processes, and expression of DC surface markers, including DEC-205, CD11c, B7.1, and B7.2. These effects were observed in both PU5-1.8 cells and splenocytes from various mouse strains including BALB/c, C57BL/6, NOD/Lt, and C3H/HeJ. Coadministration of Ep1.B with OVA antigenic peptide functions in dampening specific immune response to OVA. Ep1.B down-regulates proliferation of T cells and IFN-gamma production and stimulates IL-10 secretion in immunized mice. Ep1.B-induced differentiation resulted in the activation of PI3K and MAPK signaling pathways, including ERK1/2, p38, and JNK. We also found that NF-kappaB, a transcription factor essential for DC differentiation, is critical in mediating the effects of Ep1.B. Ep1.B-induced differentiation is independent of MyD88-dependent pathway of TLR signaling. Cumulatively, these findings suggest that Ep1.B acts by initiating a signal transduction cascade in monocytes leading to their differentiation into DCs.

Altered immunodominance hierarchies of influenza A virus-specific H-2(b)-restricted CD8+ T cells in the absence of terminal deoxynucleotidyl transferase

Immunodominance is considered an obstacle to successful T cell-based vaccination, and constant efforts are made to uncover the underlying mechanisms for this phenomenon. We have examined the contribution of terminal deoxynucleotidyl transferase (TdT), whose function accounts for approximately 90% of T cell receptor diversity, to dominance hierarchies of H-2(b)-restricted flu-specific T(CD8+). Using intracellular cytokine staining to quantitatively detect epitope-specific T(CD8+), we demonstrate that TdT-deficient mice exhibit a distinct hierarchical pattern in their primary and recall T(CD8+) responses to influenza A viruses, which results from skewed responsiveness towards select influenza epitopes. Our data establish a link between TdT and immunodominance in H-2(b)-restricted antiviral T(CD8+) responses.

IP3Rs are sufficient for dendritic cell Ca2+ signaling in the absence of RyR1

Calcium (Ca(2+)) signaling plays a pivotal role in the function of dendritic cells (DC). The Type 1 ryanodine receptor (RyR), a major intracellular Ca(2+) channel, is highly expressed in immature DC. We therefore investigated whether RyR1 plays a role in DC development and function by studying properties of DC derived from wild-type (WT) and RyR1 null [knockout (KO)] mice. Fetal liver cells from WT and RyR1 KO mice retained full hematopoietic competence. Adoptive transfer of these cells into congenic hosts resulted in the generation of functionally equivalent DC populations. WT and RyR1 KO DC exhibited a similar capacity to mature in response to inflammatory and/or activation stimuli, to endocytose antigen, and to stimulate T cell proliferation. Moreover, the absence of RyR1 did not lead to de novo expression of RyR2 or RyR3. WT and RyR KO DC express all three isoforms of inositol 1,4,5-trisphosphate receptor (IP(3)R), although Type 3 IP(3)R gene transcripts are predominant. Further, IP(3)-mediated Ca(2+) transients proceed normally after inhibition of RyRs with dantrolene. Signaling via IP(3)R may therefore be sufficient to drive essential DC Ca(2+) signaling processes in the absence of RyR expression or function.

A novel form of immune signaling revealed by transmission of the inflammatory mediator serotonin between dendritic cells and T cells

Adaptive immunity is triggered at the immune synapse, where peptide-major histocompatibility complexes and costimulatory molecules expressed by dendritic cells (DCs) are physically presented to T cells. Here we describe transmission of the inflammatory monoamine serotonin (5-hydroxytryptamine [5-HT]) between these cells. DCs take up 5-HT from the microenvironment and from activated T cells (that synthesize 5-HT) and this uptake is inhibited by the antidepressant, fluoxetine. Expression of 5-HT transporters (SERTs) is regulated by DC maturation, exposure to microbial stimuli, and physical interactions with T cells. Significantly, 5-HT sequestered by DCs is stored within LAMP-1+ vesicles and subsequently released via Ca2+-dependent exocytosis, which was confirmed by amperometric recordings. In turn, extracellular 5-HT can reduce T-cell levels of cAMP, a modulator of T-cell activation. Thus, through the uptake of 5-HT at sites of inflammation, and from activated T cells, DCs may shuttle 5-HT to naive T cells and thereby modulate T-cell proliferation and differentiation. These data constitute the first direct measurement of triggered exocytosis by DCs and reveal a new and rapid type of signaling that may be optimized by the intimate synaptic environment between DCs and T cells. Moreover, these results highlight an important role for 5-HT signaling in immune function and the potential consequences of commonly used drugs that target 5-HT uptake and release.

Polycationic lipids inhibit the pro-inflammatory response to LPS

Lipopolysaccharide (LPS) is a major component of the outer membrane of Gram-negative bacteria. As such, it signals monocytes, macrophages and neutrophils to up-regulate phagocytic functions and to release pro-inflammatory cytokines. Despite the established role of CD14 as the main LPS receptor, the precise nature of the LPS signalling complex and its compartmentalization remain unknown. Interactions of LPS with other cell surface molecules such as TLR-4 and MD-2, and its subsequent internalization are required for LPS signalling. Here, we show that the polycationic lipid LipoFectamine causes inhibition of the LPS-induced MAPK activation and lack of pro-inflammatory cytokine production, despite proper localization of CD14 within lipid rafts and massive LPS internalization. The ability of LipoFectamine to inhibit LPS induced pro-inflammatory responses may be due to uncoupling of CD14 from TLR-4/MD-2 in the LPS signalling complex of mouse macrophages/microglial cells, as suggested by inhibition of LPS-induced concomitant internalization of these surface molecules. Thus, LipoFectamine may be a useful tool to dissect the molecular interactions leading to LPS signalling, and identifies a potential therapeutic strategy for LPS clearance.

Comparative performances of an HTLV-I/II EIA and other serologic and PCR assays on samples from persons at risk for HTLV-II infection

BACKGROUND

HTLV-I and HTLV-II are related exogenous pathogenic human retroviruses. Until recently, ELISAs based on HTLV-I antigens have been used to screen for the presence of HTLV-I or -II antibodies. The HTLV-I-based assays have not been as sensitive in detecting antibodies to HTLV-II as in detecting antibodies to HTLV-I. The Abbott HTLV-I/HTLV-II ELISA uses a combination of HTLV-I and HTLV-II antigens to detect antibodies to the whole HTLV group. The performance of this ELISA was compared to that of several HTLV-I-based serologic assays and an HTLV-II PCR assay in cohorts of South American Indians and New York City IV drug users (IVDUs) in whom HTLV-II is endemic.

STUDY DESIGN AND METHODS

Sera from 429 South American Indians and New York City IVDUs were evaluated for HTLV antibodies by the use of three ELISAs (rgp21-enhanced HTLV-I/II, Cambridge Biotech; Vironostika HTLV-I/II, Organon Teknika; and HTLV-I/HTLV-II, Abbott), and a Western blot (WB) assay. Peripheral blood leukocyte DNA from each person was analyzed for HTLV-I and HTLV-II pol DNA via PCR. The HTLV-II PCR-positive samples were further subtyped via cloning and sequencing and/or oligomer restriction.

RESULTS

Two hundred four samples (48%) were positive for HTLV-II by serologic and/or PCR assays. All of the positive samples from the Indians and approximately one-third of the positive samples from the IVDUs were of the HTLV-IIB subtype. Comparative analyses indicate that the sensitivity and specificity of the various assays were: PCR, 98 and 100 percent; Abbott HTLV-I/HTLV-II, 78 and 95 percent; Cambridge Biotech HTLV-I/II, 76 and 96 percent; Vironostika HTLV-I/II, 71 and 98 percent; and WB, 73 and 100 percent, respectively.

CONCLUSION

There were no significant differences among the sensitivities and specificities of the HTLV-I/II ELISAs (p values, 0.056-0.438). The WB and PCR assays were much more specific than the other serologic assays (p</=0.03). However, the PCR assay is significantly (p<0.001) more sensitive than any of the serologic assays in the detection of HTLV-II infection. Thus, optimal detection of HTLV-II infection would seem to require both serologic and DNA PCR assays.

The complete genomic sequence of an HTLV-II isolate from a Guahibo Indian from Venezuela

A polyclonal CD3(+), CD8(+) T-cell line, G2, was derived from the peripheral blood of a seropositive, PCR-positive, HTLV-IIB infected Guahibo Indian from Venezuela. The cell line is productively infected with HTLV-IIB. The entire HTLV-II G2 proviral DNA was sequenced via PCR using overlapping HTLV-II primer pairs. Phylogenetic analyses indicate that HTLV-II G2 is the most divergent HTLV-IIB strain identified to date. Characterization of its deduced proteins and its relationship to other members of the PTLV/BLV genus of retroviruses are discussed.

Endemic infection with HTLV-IIB in Venezuelan Indians: molecular characterization

The peripheral blood of 41 Yaruro and Guahibo Indians from Venezuela was examined for HTLV antibodies and DNA. Twenty-five samples (61%) were found to be infected with HTLV-IIB. The sensitivities of the serologic and DNA polymerase chain reaction (PCR) analyses were 80% and 96%, respectively. Epidemiologic studies supported both sexual and perinatal transmission of the virus. Sequence analyses of the HTLV-IIB strains from these Indians indicate that they are unique relative to HTLV-II detected in other groups of humans. HTLV-IIB-G2 isolated from a Guahibo Indian is the most divergent HTLV-IIB strain relative to the prototype HTLV-II NRA.

Highly endemic human T-lymphotropic virus type II (HTLV-II) infection in a Venezuelan Guahibo Amerindian group

Sera from 166 Guahibo Indians (55% of the population) living in southwest Venezuela were screened by enzyme-linked immunoassay for antibodies to human T-cell lymphotropic virus (HTLV) I and II. Positive samples were confirmed by immunofluorescence and Western blot. Forty-one Guahibos (24.8%) were found to be seropositive. Polymerase chain reaction (PCR) analysis of proviral DNA in mononuclear cell lysates revealed the virus to be HTLV-II. Prevalence increased with age, and sexual contact with HTLV-II-seropositive partners was identified as a risk factor for infection. PCR amplification of a region of the pol gene, utilizing the primer pair SK110/SK111, with subsequent digestion of the 140-base-pair amplification products with HinfI and MseI restriction enzymes, showed an HTLV-II subtype-b restriction pattern in all cases. These data suggest that the substrain infecting this Guahibo community belongs to the b subtype, the most frequent among Paleo-Amerindian populations.

First description of endemic HTLV-II infection among Venezuelan Amerindians

We describe for the first time the presence of human T lymphotropic virus type II (HTLV-II) infection in Venezuela, among the Pume Amerindians living in the southern plains of the country. Antibodies to HTLV-II antigens were assessed by enzyme immunoassays (Elisa), Western blot, radioimmuno-precipitation, and immunofluorescence; titration studies against HTLV-I- and HTLV-II-infected cell lines were very useful in the differentiation of HTLV-I and HTLV-II antibodies. The HTLV-II general prevalence was 5%; however, there is a striking difference in prevalence between the truly isolated villages (0%) when compared to those living along the riverside and thus in contact with outsiders (9%). Preliminary evidence suggests sexual contact as the main source of transmission. These findings might suggest that HTLV-II in Venezuela originated through contact with outsiders rather than ancient infection related to the origins of the Pume.

Increased proportion of responders to a murine anti-CD3 monoclonal antibody of the IgG1 class in patients with systemic lupus erythematosus (SLE)

A group of Venezuelan patients with SLE showed an increased proportion of responders to Leu-4, an anti-CD3 MoAb of the IgG1 class, compared with ethnically matched non-SLE patients and healthy controls. The rate of proliferative responses or IL-2 production induced by MoAb Leu-4, and the helper effect of macrophages from Leu-4 responders on T cells from a third-party donor were comparable in patients and controls. No significant differences in the binding of murine IgG1 molecules by macrophages from SLE patients and controls were observed. The proportion of monocytes/macrophages expressing Fc gamma RI was significantly higher in SLE patients. However, the expression of FcRII, the type capable of supporting Leu-4-mediated responses, and of Fc gamma RIII was comparable in monocytes from SLE patients and controls. Our results suggest that Venezuelan patients with SLE may have a genetic predisposition for the expression of the phenotypic variant of Fc gamma RII capable of binding murine IgG1 molecules.

Bone marrow and peripheral blood natural killer cell activity in lymphomas. Its response to IL-2

Natural killer (NK) cytotoxic activity was simultaneously investigated in bone marrow mononuclear cells (BMMC) and peripheral blood lymphocytes (PBL) from nine Hodgkin's disease (HD) and 15 non-Hodgkin lymphoma (NHL) untreated patients. Twenty-five PBL samples and seven bone marrow specimens from healthy individuals were also included as control group (C). NK cell activity was evaluated in basal condition and post-stimulation with human recombinant IL-2 (rIL-2). Data were expressed in K values (number of BMMC or PBL needed to lyse 50% of the target cells). In basal condition, both HD and NHL patients showed a NK cell activity comparable to the C group, both in BMMC (HD, K = 2.48 +/- 1.3; NHL, K = 3.8 +/- 2.0; C, K = 3.2 +/- 0.7) and PBL (HD, K = 2.0 +/- 1.0; NHL, K = 2.3 +/- 1.0; C, K = 2.2 +/- 0.2). Stimulation with rIL-2 induced a significant and comparable enhancement of the NK activity in PBL from HD, NHL and C while the response to rIL-2 of the BMMC in most of the HD and NHL patients was significantly greater than the C group. Responder cells were characterized by negative selection with specific MoAb plus complement as a CD3-, CD16+, CD56+ cytotoxic cell and further confirmed by flow cytometry. We postulate that IL-2 activation of bone marrow NK cell precursors, in addition to enhancing the activity of circulating NK, may be of value for the therapeutic rationale of IL-2 in patients with lymphoma.

Enhanced CD3-mediated T lymphocyte proliferation in patients with systemic lupus erythematosus

Nonfractionated peripheral blood lymphocytes from patients with systemic lupus erythematosus (SLE) showed enhanced proliferative responses when stimulated via the CD3 pathway. In contrast, proliferative responses induced by phytohemagglutinin were diminished in SLE patients. Levels of CD3-induced interleukin-2 production and interleukin-2 receptor expression were comparable with normal levels. Highly purified T cells also showed augmented CD3 responses, but only in the presence of phorbol myristate acetate or a combination of phorbol myristate acetate plus calcium ionophore A23187, and not with calcium ionophore alone. The data suggest integrity of the T cell receptor/CD3 pathway for T cell activation in patients with SLE, as examined in cultures stimulated with specific anti-CD3 monoclonal antibodies rather than with multivalent lectins. An increased response via the CD3 complex could contribute to the autoimmune activity in human SLE.

Human IFN-gamma up-regulates IL-2 receptors in mitogen-activated T lymphocytes

This study examined the role of human recombinant interferon-gamma (rIFN-gamma) in the expression of interleukin-2 receptors (IL-2R) by human T lymphocytes. rIFN-gamma enhanced total numbers of IL-2R in mitogen-activated but not resting T cells. Scatchard plot analysis indicated that rIFN-gamma increased both high- and low-affinity receptors, with a predominant effect on the latter. Phytohaemagglutinin (PHA)-activated T cells treated with IFN-gamma showed higher IL-2 binding and greater IL-2 internalization and degradation than cells treated with PHA alone. There was a corresponding increase of mitogen-driven proliferative responses, indicating an increase of functional receptors in IFN-treated cultures. IFN-gamma may influence T-cell activation and proliferation by enhancing expression of IL-2R and promoting IL-2 uptake by mitogen-activated lymphocytes.

Down-regulation of immunoglobulin and IgM-rheumatoid factor synthesis by oral treatment of rheumatoid arthritis patients with a nonsteroidal antiinflammatory drug

We examined the effect of treatment with piroxicam, a nonsteroidal antiinflammatory drug (NSAID), on immunoglobulin (Ig) and IgM-rheumatoid factor (IgM-RF) synthesis in vitro by lymphocytes of patients with rheumatoid arthritis (RA). Oral treatment with piroxicam induced a progressive decrease of spontaneous IgM-RF production by unstimulated lymphocyte cultures during 12 weeks of observation. Also, pokeweed mitogen (PWM)-driven Ig synthesis was significantly diminished and the effect on total IgM production was sustained until the end of the study. This modulation of humoral responses is consistent with the drop in RF sera level. In addition, we also showed that treatment with NSAIDs can decrease RF levels in the synovial space. NSAIDs may have a long-term beneficial effect in patients with RA due to their modulatory role of lymphocyte responses.

Helper activity by human large granular lymphocytes in in vitro immunoglobulin synthesis

In the present study we have examined the effect of human large granular lymphocytes (LGL) from healthy donors on Ig synthesis by autologous B lymphocytes. The results showed that this cell population has a consistent helper activity in pokeweed mitogen-activated cultures even when added at very low numbers. LGL can mediate their effect by secreting soluble helper factors capable of modulating B-cell responses as evidenced by the enhancement of IgG and IgM production by supernatants obtained from LGL cultures. Preincubation with interferon gamma further potentiated the helper activity by LGL.

Abnormal immunoglobulin and rheumatoid factor synthesis by blood lymphocytes in patients with primary Sjögren's syndrome

Peripheral blood B lymphocytes from patients with primary Sjögren's syndrome showed significantly higher spontaneous synthesis of IgG, IgM, and IgM rheumatoid factor in vitro, compared with B lymphocytes from healthy controls. Lymphocytes from patients also showed higher IgM rheumatoid factor production after mitogen stimulation. Patients had competent suppressor activity for IgG, but not for IgM synthesis. Pre-irradiation of T cells, but not depletion of OKT8+ cells, markedly enhanced IgG synthesis in cocultures with autologous B cells; therefore, the T lymphocyte responsible for this effect is radiosensitive and is not identified by OKT8. OKT8+ lymphocytes from patients did not suppress Ig synthesis by autologous B plus T cell cocultures. However, OKT8+ cells from normal controls down-regulated Ig synthesis by B plus T cells from patients. The abnormal proportion of helper and suppressor cells suggests that there is altered redistribution of regulatory subpopulations in peripheral blood from Sjögren's syndrome patients.