A micro-costing analysis of nutritional support for persons with TB and their families in India

Undernutrition is the leading risk factor for TB infection and death in India. We undertook a micro-costing analysis of a nutritional intervention for household contacts of people living with TB in Puducherry, India. We found that the total 6-month food cost for a family of four was USD4/day. We also identified several alternative regimens and cost-lowering strategies to encourage wider adoption of nutritional supplementation as a public health tool.

Sustained effect of isoniazid preventive therapy among household contacts in Brazil

BACKGROUND: Isoniazid preventive therapy (IPT) is highly effective in preventing TB disease; however, its long-term benefit in household contacts (HHCs) of infectious TB cases is unclear.METHODS: We conducted a retrospective analysis of two household contact studies in Vitoria, ES, Brazil, between 2008 and 2015. Households with smear-positive, culture-proven TB disease were enrolled. Eligible HHCs with tuberculin skin test (TST) indurations of ≥10 mm were referred to local TB clinics and IPT was started according to national guidelines. We reviewed the national dataset information system in January 2020 to identify HHCs with a diagnosis of TB disease. Time to event and Cox proportional regression analysis were conducted to identify factors associated with TB disease.RESULTS: Of the 1097 HHCs enrolled, 654 (60%) had TST ≥10 mm; 160 (24%) initiated IPT, of whom 115 (71.9%) completed IPT, which accounts for an overall completion rate of 18% among the population at risk; 42 (6%) TB cases were identified. IPT was associated with a 71% decrease in TB disease rates (HR 0.29, 95% CI 0.10-0.82; P = 0.02) among HHCs with TST ≥10 mm. IPT effect was sustained, as TB cases in HHCs without IPT occurred along the 7.9-year follow-up, whereas all four TB cases in HHCs with IPT were diagnosed within the first 3 years after exposureCONCLUSION: Isoniazid provides long-term protection for TB disease in household contacts of culture-proven TB cases.

QuantiFERON®-TB Gold In-Tube reliability for immigrants with parasitic infections in Boston, USA

<sec id="st1"> <title>SETTING</title> Accurate testing and treatment for latent tuberculous infection is necessary for tuberculosis elimination. Certain parasite infections are associated with increased tuberculin skin test positivity; species-specific effects on QuantiFERON^®-TB Gold In-Tube (QGIT) have not been described. </sec> <sec id="st2"> <title>OBJECTIVE</title> To determine whether infection with helminths or protozoa affects QGIT results. </sec> <sec id="st3"> <title>DESIGN</title> We retrospectively analyzed QGIT and parasite testing results for immigrants screened in Boston, MA, USA, from 2012 to 2017. We also prospectively measured cytokines in QGIT supernatants for a subset (n = 68) with 1) helminths, 2) Blastocystis hominis, 3) other protozoa, and 4) no parasites. </sec> <sec id="st4"> <title>RESULTS</title> Of 527 immigrants screened, 141 (26.8%) were QGIT-positive and 229 (43.4%) had parasites detected: 27/527 (5.1%) had helminths and 202/527 (38.3%) protozoa. Cytokine analysis revealed increased interleukin-10 concentrations with protozoa (P = 0.04), and non-significantly higher T-helper 2 concentrations with helminths compared with no parasites. No significant differences emerged in QGIT positivity or interferon-gamma concentrations in any group. </sec> <sec id="st5"> <title>CONCLUSION</title> Study results support the use of QGIT in parasite-endemic settings. </sec>.

Nippostrongylus brasiliensis infection modulates Mycobacterium tuberculosis induced Th1 response (43.45)

Modulation of Th1 response generated against pathogens like M tuberculosis (Mtb) by helminths is an important, area of investigation, because of the prevalence of coinfections in TB endemic regions. In this study we have designed an approach to investigate how the Th1 response generated by Mtb is modulated by helminthic infection. We have used the ovalbumin – specific TCR transgenic adoptive transfer system, wherein the ability of Mtb-pulsed dendritic cells to initiate a Th1 response was studied on the background of a helminth infection. BALB/c mice were infected with N. brasiliensis, and groups of uninfected and infected mice were injected with CFSE labeled OVA-specific TCR transgenic T cells followed by intratracheal instillation of Mtb and ovalbumin peptide-pulsed bone marrow-derived dendritic cells. Analysis of the labeled transgenic T cells harvested from the draining lymph nodes indicated proliferation of T cells from both groups of mice. However, we observed significantly reduced level of IFNγ and a reciprocal increase in IL-4 in T cells derived form the helminth-infected mice. These findings indicate that helminth infection does not abrogate the priming ability of Mtb-pulsed DCs, but interferes with their ability to promote a Th1 response. The significance of the findings lies in the potential of helminth infections to modulate resistance to tuberculosis, and also to interfere with the efficacy of tuberculosis vaccines.

B7-1 and B7-2 co-stimulatory molecules are required for mercury-induced autoimmunity

B7-1 (CD80) and B7-2 (CD86) molecules on antigen presenting cells play important roles in providing co-stimulatory signals required for activation and expansion of autoreactive T cells. Moreover, some reports have suggested that these molecules may have distinct functions in the differentiation of Th1 and Th2 cells. Mercury-induced autoimmunity in H-2s mice is characterized by lymphoproliferation of T and B cells, serum increases in IgG1 and IgE and production of antinucleolar antibodies (ANoA). The mechanisms responsible for the various manifestations of this syndrome have yet to be elucidated. To examine the contributions of B7 co-stimulatory molecules to this model, susceptible mice were treated with antibodies to B7-1, B7-2, or both during the development of mercury-induced autoimmunity. The combination of anti-B7-1 and anti-B7-2 antibodies prevented Hg-induced disease in H-2s mice. Additionally, single anti-B7-1 antibody treatment was sufficient to prevent Hg-induced ANoA production, but not IgG1 and IgE hypergammaglobulinaemia. Further, single antibody treatment with anti-B7-2 resulted in a partial reduction of ANoA titres but had no significant effect on total serum IgG1 and IgE levels. Taken together, these results indicate that B7-1 and B7-2 molecules are critical for the development of Hg-induced autoimmunity and suggest that the different manifestations of the syndrome are regulated by independent mechanisms.

Reciprocal induction of IL-10 and IL-12 from macrophages by low-density lipoprotein and its oxidized forms

Atherosclerosis is a chronic inflammatory disease. Several lines of evidence indicate that altered or modified lipoproteins contribute to plaque formation and lesion progression in atherogenesis. In this study we examined if lipoproteins and their oxidized forms can exert an immunomodulatory effect, thereby potentially influencing atherogenesis. We demonstrate that LDL, upon binding to its receptor, induces interleukin (IL)-10 production from macrophages and biases naive T cells to become Th2-like. In contrast, oxLDL induces IL-12 from macrophages and accordingly favors differentiation of naive T cells along a Th1 pathway. IL-10 is a potent anti-inflammatory cytokine with a number of potential effects that could dampen inflammation at sites of vascular wall damage, including downregulation of MHC and adhesion molecules and biasing of adaptive immune responses toward the anti-inflammatory, humoral immune-promoting Th2 T cell subset. These studies assign a new immunomodulatory role to LDLs and offer a potential means to upregulate IL-10 production and prevent arterial inflammation.

Phosphatidylinositol 3′-Kinase Blocks CD95 Aggregation and Caspase-8 Cleavage at the Death-Inducing Signaling Complex by Modulating Lateral Diffusion of CD95

Activation of phosphatidylinositol 3'-kinase (PI 3'-K) after ligation of CD3 protects Th2 cells from CD95-mediated apoptosis. Here we show that protection is achieved by inhibition of the formation of CD95 aggregates and consequent activation of caspase-8. Inhibition of aggregate formation is mediated by changes in the actin cytoskeleton, which in turn inhibit lateral diffusion of CD95, reducing its diffusion coefficient, D, 10-fold. After cytochalasin D treatment of stimulated cells, the lateral diffusion of CD95 increases to the value measured on unstimulated cells, and CD95 molecules aggregate to process caspase-8 and mediate apoptosis. Regulation of functional receptor formation by modulating lateral diffusion is a novel mechanism for controlling receptor activity.

Mycobacterium tuberculosis infection in complement receptor 3-deficient mice

Complement receptor type 3 (CR3) present on macrophages is used by Mycobacterium tuberculosis as one of its major phagocytic receptors. In this study, we examined the in vivo significance of CR3-mediated phagocytosis on the pathogenesis of disease caused by M. tuberculosis. The outcome of tuberculous infection in mice deficient in the CD11b subunit of CR3 (CR3-/-) on a mixed 129SV and C57BL background and control wild-type counterparts was comparable with respect to survival, bacterial burden, granulomatous lesion development, and cytokine expression in the spleen and lungs. M. tuberculosis infection was also examined in CR3-/- mice on C57BL/6 and BALB/c backgrounds and was found to be similar. In conclusion, our results suggest that in the absence of CR3, M. tuberculosis is able to gain entry into host cells via alternative phagocytic receptors and establish infection. The data also indicate that absence of CR3 does not alter disease course in either the relatively resistant C57BL/6 or the relatively susceptible BALB/c strains of mice.

Rescue of human T cells by interleukin-9 (IL-9) from IL-2 deprivation-induced apoptosis: correlation with alpha subunit expression of the IL-9 receptor

Interleukin-9 (IL-9) is a Th2-derived cytokine that uses the gamma-chain of the IL-2 receptor for signaling. Therefore, the responsiveness of human Th1 and Th2 cell clones to IL-9 was measured by examining the ability of this cytokine to prevent apoptosis induced by IL-2 deprivation. A time course study demonstrated that both subsets of T cell clones underwent apoptosis with similar kinetics when deprived of IL-2 and that viability could be maintained by the addition of either IL-4 or IL-7. Interestingly, IL-9 prevented apoptosis in only 2 (Th2) of 14 clones tested. Analysis of IL-9R alpha subunit expression on 18 T cell clones revealed that IL-9 responsiveness was directly proportional to the expression of the high-affinity receptor. IL-9 responsiveness was also dependent on long-term culturing because neither freshly isolated nor 3-day phytohemagglutinin (PHA)-stimulated peripheral blood lymphocytes (PBL) expressed IL-9R alpha. In summary, the data showed that IL-9 can rescue only a small subset of Th2 cells from apoptosis induced by growth factor withdrawal and that expression of IL-9R alpha is required for the antiapoptotic signals mediated by this cytokine.

Selective up-regulation of phosphatidylinositol 3'-kinase activity in Th2 cells inhibits caspase-8 cleavage at the death-inducing complex: a mechanism for Th2 resistance from Fas-mediated apoptosis

In this study the mechanism of differential sensitivity of CD3-activated Th1- and Th2-type cells to Fas-mediated apoptosis was explored. We show that the Fas-associated death domain protein (FADD)/caspase-8 pathway is differentially regulated by CD3 activation in the two subsets. The apoptosis resistance of activated Th2-type cells is due to an incomplete processing of caspase-8 at the death-inducing signaling complex (DISC) whereas recruitment of caspase-8 to the DISC of Th1- and Th2-like cells is comparable. Activation of phosphatidylinositol 3'-kinase upon ligation of CD3 in Th2-type cells blocked caspase-8 cleavage to its active fragments at the DISC, thereby preventing induction of apoptosis. This study offers a new pathway for phosphatidylinositol 3'-kinase in mediating protection from Fas-induced apoptosis.

Cytokine regulation of a rodent model of mercuric chloride-induced autoimmunity

Experimental models of chemically induced autoimmunity have contributed to our understanding of the development of autoimmune diseases in humans. Heavy metals such as mercury induce a dramatic activation of the immune system and autoantibody production in genetically susceptible rats and mice. This autoimmune syndrome is dependent on T cells, which are important for B-cell activation and cytokine secretion. Several studies have focused on the roles of T-helper (Th)1 and Th2 cells and their respective cytokines in the pathogenesis of mercury-induced disease. This article reviews recent studies that have examined the patterns of cytokine gene expression and where investigators have manipulated the Th1 and Th2 responses that occur during mercury-induced autoimmunity. Finally, we will discuss some biochemical/molecular mechanisms by which heavy metals may induce cytokine gene expression.

Murine mercury-induced autoimmunity: a model of chemically related autoimmunity in humans

Human exposure to certain compounds or therapeutic drugs can result in the development of an autoimmune syndrome. Mercury (Hg) induced autoimmunity is one of the few animal models in which administration of a chemical induces a specific loss of tolerance to self-antigens. After receiving subtoxic doses of Hg or other heavy metals, susceptible mouse strains rapidly develop highly specific antibodies to nucleolar antigens. In addition, these animals display a general activation of the immune system, especially pronounced for the Th2 subset and a transient glomerulonephritis with immunoglobulin deposits. Like many human autoimmune diseases, this syndrome is associated with the expression of susceptible major histocompatibility complex (MHC) class II genes. In this article, we review the essential features of this model, and we discuss the putative mechanisms by which Hg creates such a severe immune dysfunction.

Inability of interleukin-12 to modulate T-helper 0 effectors to T-helper 1 effectors: a possible distinct subset of T cells

Interleukin-12 (IL-12) strongly favours the development of T-helper 1 (Th1)-type cells through its ability to induce interferon-gamma (IFN-gamma) production by natural killer cells and T cells. In the present work we analysed the effects of IL-12 on the synthesis and secretion of IFN-gamma and IL-4 by human T-cell clones. Several previously described human T-cell clones exhibiting Th1, Th2 or Th0 phenotypes were used for these analyses. We demonstrated, by enzyme-linked immunosorbent assay (ELISA) and intracytoplasmic staining, that, in Th0 clones, IL-12 up-regulated the production of both IFN-gamma and IL-4 and was unable to modulate these cells to Th1-type. The up-regulation of cytokine gene expression was transcriptionally regulated and was not due to differences in mRNA stability. In Th1 cells, IL-12 up-regulated only IFN-gamma and not IL-4. However, in Th2 cells, both IFN-gamma and IL-4 were up-regulated by IL-12. This suggests that Th2 cells may be less stable than Th1 cells. We also observed that human Th2 cells expressed the IL-12beta2 receptor, in contrast to murine Th2, which lacks this receptor. The observed differences in the effects of IL-12 on the three T-cell subsets may have important ramifications for IL-12-based therapies.

CD95 mediated T cell apoptosis and its relevance to immune deviation

The CD95/CD95L pair plays a manifold role in regulating life and death in the function of the immune system. Examples include CD95/CD95L acting as cytotoxic CD8+ T cell effector molecules, or functioning on CD4+ T helper cells to maintain peripheral tolerance or reestablishing homeostasis. Current understanding of the CD95 signaling pathway reveals several potential regulatory targets, acting both receptor proximally and distally, that can terminate or amplify the receptor's signal. The important and possibly non-redundant role of CD95 is highlighted both in how deficiencies in functional CD95 or its ligand manifest themselves in autoimmune syndromes, and how uncontrolled cell death results in insufficient, or inappropriate immune responses against immune challenge. This review examines CD95-mediated signal transduction, and the effect preferential apoptosis of T helper cell subsets has on immune system biasing.

Mercury-induced autoimmunity in the absence of IL-4

In susceptible H-2S mice, mercuric chloride (HgCl2) induces an autoimmune syndrome characterized by production of anti-nucleolar antibodies (ANoA) and increased serum levels of IgG1 and IgE antibodies. The increase in serum IgG1 and IgE, which are under IL-4 control, suggests a role for the Th2 subset in the induction of this syndrome. We have previously shown that administration of IL-12, a potent Th1-promoting cytokine, resulted in a dramatic reduction of the HgCl2-induced anti-nucleolar antibody titres and inhibited serum IgG1 increase. These results suggest that Th1 T cells can down-regulate ANoA, and support a role for the Th2 subset in ANoA production, possibly via IL-4. To examine the role of IL-4 in this syndrome, C57Bl/6 mice (H-2b) with a targeted deletion of the IL-4 gene were mated with A.SW mice (H-2S) to yield H-2S mice lacking IL-4. We then analysed ANoA and serum immunoglobulin levels in these mice after HgCl2 treatment. While mercury-treated IL-4(-/-) H-2S mice had virtually no detectable serum IgG1 or IgE, and very low levels of IgG1 ANoA, these mice had levels of IgG2a and IgG2b class ANoA comparable to mercury-treated IL-4+ H-2S mice, indicating that IL-4 is not required for the ANoA response in mercury-induced autoimmunity.

Th2-specific protein/DNA interactions at the proximal nuclear factor-AT site contribute to the functional activity of the human IL-4 promoter

IL-4 is a pleiotropic immunoregulatory cytokine secreted by activated Th2, but not Th1, cells. The proximal IL-4 promoter contains MARE, C/EBP, P0, octamer-like, P1, and activating protein-1 elements. The half c-Maf binding site (MARE), P0, and P1 sites were previously shown to be involved in Th2-specific transcriptional activity. Except the MARE and P1 site, the molecular basis for Th2 specificity of the P0 site has not been analyzed. Here, we provide the first detailed analysis of the P0 binding factors and show that in Th2, but not in Th1, cells, NF-AT and proteins of the activating protein-1 family are involved in cooperative binding to the P0 and the adjacent octamer-like site. In the mouse Th2 D10 cells, Oct-1/Oct-2 are also found to participate in formation of the P0-binding complexes. Mutation, deletion, and methylation interference analysis demonstrate that both the P0 and the octamer-like sequence are required for inducible binding. Furthermore, we provide the first report of the functional relevance of each site in the human IL-4 promoter by mutagenesis/transfection analysis and demonstrate that the octamer-like, P0 and P1 sites are important for the biologic function of the IL-4 promoter. The MARE site, although it was shown to be critical for the function of the murine IL-4 promoter, does not appear essential for human IL-4 promoter activity in Jurkat T cells. These findings suggest that besides c-Maf, another Th2-specific factor(s) may be involved in tissue-specific expression of the IL-4 gene.

T cells and T-cell cytokine transcripts in the synovial membrane in patients with osteoarthritis

The synovial membrane in osteoarthritis (OA) often exhibits inflammatory infiltrates, but the role of T cells in these infiltrates is not known. T-cell activation antigens were analyzed by immunohistochemistry, and T-cell cytokine transcripts were measured by competitive PCR in synovial membranes from patients with OA and rheumatoid arthritis (RA). Lymphoid cell aggregates, containing primarily CD3+ T lymphocytes, were found in 65% of patients with OA. Mononuclear cells expressing the activation antigens CD69, CD25, CD38, CD43, CD45RO, and HLA class II were present in both patient groups, although in higher numbers in patients with RA. Interleukin 2 (IL-2) transcripts were found in 10 of 18 patients with OA versus 12 of 13 patients with RA (P = 0.03). Gamma interferon (IFN-gamma) transcripts were detected in 9 of 18 patients with OA versus 10 of 13 patients with RA (not significant), whereas IL-10 transcripts were found in nearly all patients. IL-4 and IL-5 were not detected in any patients. The levels of IFN-gamma and IL-2 transcripts, normalized for T-cell number equivalents, were not statistically different between OA and RA, but the levels of IFN-gamma, normalized for total cell number equivalents, were lower in OA than in RA (P = 0.01). Synovial membranes that expressed IL-2 and IFN-gamma transcripts were more likely to have heavier infiltrations of T cells and cells bearing activation markers than synovial membranes that did not express these cytokines. The presence of activated T cells and TH1 cytokine transcripts in chronic joint lesions of patients with OA suggests that T cells contribute to chronic inflammation in a large proportion of these patients.

Infection of T cell subsets by HIV-1 and the effects of interleukin-12

CD4+ lymphocytes constitute one of the major cell targets for human immunodeficiency virus type 1 (HIV-1) infection. The eventual loss of CD4+ lymphocytes contributes substantially to the pathogenesis of HIV-1 and development of acquired immunodeficiency syndrome (AIDS). CD4+ lymphocytes consist of the subgroups Th1, Th2, and Th0, which differ in their cytokine profile. Th1 cells produce cytokines that favor cell-mediated immune responses, whereas Th2 cells produce cytokines that favor humoral immunity. Th0 cells are precursors to the Th1 and Th2 subsets. A shift from a Th1 to a Th2 response has been reported for HIV-1-infected patients (Kannagi et al. 1990. J. Virol. 64, 3399-3406; Walker et al. 1986. Science 234, 1563-1566; Walker et al. 1991. J. Virol. 65, 5921-5927). For this reason, the potential role of cytokines in the development of AIDS has received a great deal of attention. Interleukin (IL)-12 is a disulfide-linked, 70-kDa heterodimeric cytokine produced by antigen-presenting cells. IL-12 has a central role in the development of the Th1-type immune responses. Therefore, we investigated the ability of T-tropic HIV-1 IIIB to replicate in Th1, Th2, and Th0 T cell clones and studied the effects of IL-12 on HIV-1 replication in these cells types. These studies demonstrate several points. (1) Th1, Th2, and Th0 T cell clones support HIV-1 IIIB replication nearly equally well, and it is, therefore, unlikely that differences in ability to support HIV-1 replication can explain changes in Th1, Th2, or Th0 subtype 1 following HIV-1 infection. (2) Using this model, we show that IL-12 can inhibit HIV-1 replication, consistent with a role for IL-12 in HIV-1 replication in T cells. (3) HIV-1 can form a persistent infection in T cell clones, providing a reservoir model for study of viral sanctuary and persistence in a system closely approximating the in vivo situation.

Reversal of proinflammatory responses by ligating the macrophage Fcgamma receptor type I

Macrophages can respond to a variety of infectious and/or inflammatory stimuli by secreting an array of proinflammatory cytokines, the overproduction of which can result in shock or even death. In this report, we demonstrate that ligation of macrophage Fcgamma receptors (FcgammaR) can lead to a reversal of macrophage proinflammatory responses by inducing an upregulation of interleukin (IL)-10, with a reciprocal inhibition of IL-12 production. IL-10 upregulation was specific to FcgammaR ligation, since the ligation of the Mac-1 receptor did not alter IL-10 production. The identification of the specific FcgammaR subtype responsible for IL-10 upregulation was determined in gene knockout mice. Macrophages from mice lacking the FcR gamma chain, which is required for assembly and signaling by FcgammaRI and FcgammaRIII, failed to upregulate IL-10 in response to immune complexes. However, mice lacking either the FcgammaRII or the FcgammaRIII were fully capable of upregulating IL-10 production, implicating FcgammaRI in this process. The biological consequences of FcgammaRI ligation were determined in both in vitro and in vivo models of inflammation and sepsis. In all of the models tested, the ligation of FcgammaR promoted the production of IL-10 and inhibited the secretion of IL-12. This reciprocal alteration in the pattern of macrophage cytokine production illustrates a potentially important role for FcgammaR-mediated clearance in suppressing macrophage proinflammatory responses.

IL-12 down-regulates autoantibody production in mercury-induced autoimmunity

In genetically susceptible H-2s mice, subtoxic doses of mercuric chloride (HgCl2) induce a complex autoimmune syndrome characterized by the production of anti-nucleolar IgG Abs, lymphoproliferation, increased serum levels of IgG1 and IgE Abs, and renal Ig deposits. Mercury-induced autoimmunity in H-2s mice provides a useful model for chemically related autoimmunity in humans. The increase in serum IgG1 and IgE, which are under IL-4 control, suggests a role for the Th2 subset in this syndrome. The IL-12 cytokine induces T cell proliferation and IFN-gamma production and is necessary for differentiation of naive T cells into the Th1 subset. To gain an understanding of T cell control in this syndrome and, in particular, Th1/Th2 regulation, we assessed the effect of IL-12 administration in mercury-induced autoimmunity. Groups of A.SW mice (H-2s) received HgCl2 plus IL-12, HgCl2 alone, or IL-12 alone. IL-12 treatment resulted in a dramatic reduction of the anti-nucleolar Ab titers. IL-12 also inhibited the HgCl2-induced serum IgG1 increase, but, in contrast, did not significantly affect IgE induction in this model. This observation may be related to our unexpected finding that IL-12 further potentiated the HgCl2-triggered IL-4 induction in this model. The levels of renal Ig deposits were similar in mice receiving HgCl2 alone or HgCl2 plus IL-12. Our results indicate that IL-12 can down-regulate the autoimmune component of this experimental syndrome and that the various manifestations of mercury-induced autoimmunity are independently regulated.

What controls tissue-specific expression of the IL-4 gene?

Interleukin-4 (IL-4) plays a central role in the pathogenesis of allergic inflammation by inducing Ig class switch to IgE. IL-4 is also the most potent factor that drives naive T helper (Th) cells to differentiate to the Th2 phenotype. Recently, efforts have been made to explore the molecular basis of the Th2-specific IL-4 expression in CD4 T cells. Transcription factors, such as GATA-3, NF-IL6 and c-Maf, were found to be preferentially expressed in Th2 cells and to play an important role in regulation of the IL-4 promoter activity. Yet, other transcription factors may be indirectly involved in Th2-specific expression of IL-4 even though they are present in both Th1 and Th2 cells. In conclusion, Th2-specific expression of the IL-4 gene appears to be controlled by a multi-factor-system.

Differential ability of T cell subsets to undergo activation-induced cell death

Human T cell clones were analyzed for their susceptibility to activation-induced cell death (AICD) in response to CD3/T cell receptor ligation. AICD was observed only in Th1 clones and was Fas-mediated, whereas Th2 clones resisted AICD. Analysis of a panel of Th0 clones, characterized by their ability to secrete both Th1 and Th2 cytokines, revealed that this subset included both AICD-sensitive (type A) and -resistant (type B) clones. Resistance to AICD by Th2 and Th0-type B clones was not due to lack of expression of either Fas receptor or its ligand. Paradoxically, the AICD-resistant clones were susceptible to apoptosis when Fas receptor was directly ligated by anti-Fas antibodies. However, prior activation of the resistant clones by monoclonal antibodies to CD3/TCR complex induced resistance against Fas-mediated apoptosis. Thus, the Fas-FasL pathway is critical for the induction of AICD in T cells, and moreover this pathway can be negatively regulated in the AICD-resistant clones by signals that are generated from ligation of the CD3/TCR complex.

Characterization of constitutive and inducible transcription factors binding to the P2 NF-AT site in the human interleukin-4 promoter

Interleukin-4 (IL-4) is a pleiotropic immunomodulatory cytokine secreted by T helper 2 cells. The IL-4 promoter contains multiple sites with DNA sequences homologous to the IL-2 NF-AT binding site. One of these sites--the P2 site--located between -173 and -150 was previously found to be flanked by two octamer-like motifs. NF-ATp/c and octamer proteins were suggested to bind to this region and to cooperatively activate the promoter activity (Chuvpilo et al., 1993). To precisely analyze the P2-binding factors we used antibodies against NF-ATp, NF-ATc, Fos, Jun, Oct-1 and Oct-2 in EMSA. We show here that nuclear extracts from T-cells form two P2-binding complexes--a PMA/ionomycin-inducible and a constitutive one. The PMA/ionomycin-inducible complex contains NF-ATp/c, Fos and Jun. No octamer binding factors could be detected in either of the two complexes. Analysis of the precise DNA contact points of the two complexes showed that both complexes are formed in the center of the NF-AT consensus site. No DNA contact points could be detected in the octamer-like motif site. Furthermore, purified recombinant POU domains of Oct-1 and Oct-2 failed to bind to the P2 site, suggesting that this site is not an independent octamer-binding site. Therefore, the DNA sequence at -173 to -150 of the IL-4 promoter is a binding site for NF-ATp/c and AP-1. Octamer proteins are unlikely to cooperate with NF-ATp/c at this site.

Differential interaction of nuclear factors with the PRE-I enhancer element of the human IL-4 promoter in different T cell subsets

The immunomodulatory cytokine IL-4 affects cells of most hemopoietic lineages. IL-4 is secreted by activated Th2 but not Th1 cells and plays a major role in the immune response by modulating the differentiation of naive Th cells toward the Th2 phenotype. We have previously identified an enhancer element, PRE-I, that is essential for the function of the human IL-4 promoter. To investigate the mechanisms responsible for tissue-specific expression of the IL-4 gene, we analyzed nuclear factors binding to the PRE-I site and compared the binding activities of these factors to the IL-4 promoter of Th1 and Th2 cells. We show that PRE-I interacts with PMA- and PMA/ionomycin-inducible, cyclosporin A-sensitive nuclear factors. Using anti-C/EBPbeta (NF-IL6), anti-C/EBPdelta (NF-IL6beta), anti-NF-ATc, anti-NF-ATp, anti-Fos, and anti-Jun Abs we demonstrate that the previously identified PRE-I binding factor POS-1 is composed of different transcription factors in different Th cell subsets. In the IL-4-producing Th0-like human Jurkat and mouse EL-4 cells, POS-1 (designated POS-1a) contains NF-IL6beta and Jun. In the mouse Th2 D10 cells and in the human Th2 clones, POS-1 (designated POS-1b) contains NF-IL6beta, Jun, and NF-ATc/p. In contrast, POS-1 was not found in nuclear extracts of human Th1 clones. These findings suggest that PRE-I may play a role in the differential regulation of IL-4 gene expression levels.

An ELISA for detection of apoptosis

We describe a simple and convenient enzyme-linked immunosorbent assay (ELISA) for the detection of apoptosis in tissue culture. An early event in apoptosis is DNA fragmentation followed by release of nucleosomes into the cytoplasm. Our sandwich assay uses a pair of monoclonal antibodies specific for two nucleosomal epitopes to capture and detect cytoplasmic nucleosomes onto the ELISA plate. Our assay is about 500 times more sensitive than the detection of apoptotic DNA ladder by agarose electrophoresis and is especially suited for the testing of large numbers of samples.

Differential interaction of nuclear factors with the PRE-I enhancer element of the human IL-4 promoter in different T cell subsets

The immunomodulatory cytokine IL-4 affects cells of most hemopoietic lineages. IL-4 is secreted by activated Th2 but not Th1 cells and plays a major role in the immune response by modulating the differentiation of naive Th cells toward the Th2 phenotype. We have previously identified an enhancer element, PRE-I, that is essential for the function of the human IL-4 promoter. To investigate the mechanisms responsible for tissue-specific expression of the IL-4 gene, we analyzed nuclear factors binding to the PRE-I site and compared the binding activities of these factors to the IL-4 promoter of Th1 and Th2 cells. We show that PRE-I interacts with PMA- and PMA/ionomycin-inducible, cyclosporin A-sensitive nuclear factors. Using anti-C/EBPbeta (NF-IL6), anti-C/EBPdelta (NF-IL6beta), anti-NF-ATc, anti-NF-ATp, anti-Fos, and anti-Jun Abs we demonstrate that the previously identified PRE-I binding factor POS-1 is composed of different transcription factors in different Th cell subsets. In the IL-4-producing Th0-like human Jurkat and mouse EL-4 cells, POS-1 (designated POS-1a) contains NF-IL6beta and Jun. In the mouse Th2 D10 cells and in the human Th2 clones, POS-1 (designated POS-1b) contains NF-IL6beta, Jun, and NF-ATc/p. In contrast, POS-1 was not found in nuclear extracts of human Th1 clones. These findings suggest that PRE-I may play a role in the differential regulation of IL-4 gene expression levels.

Effects of protein calorie malnutrition on tuberculosis in mice

Infectious diseases and malnutrition represent major burdens afflicting millions of people in developing countries. Both conditions affect individuals in industrialized nations, particularly the aged, the HIV-infected, and people with chronic diseases. While malnutrition is known to induce a state of immunodeficiency, the mechanisms responsible for compromised antimicrobial resistance in malnourished hosts remain obscure. In the present study, mice fed a 2% protein diet and developing protein calorie malnutrition, in contrast to well-nourished controls receiving a 20% protein diet, rapidly succumbed to infection with Mycobacterium tuberculosis. Malnourished mice exhibited a tissue-specific diminution in the expression of interferon gamma, tumor necrosis factor alpha, and the inducible form of nitric oxide synthase in the lungs, but not the liver. The expression of these molecules critical to the production of mycobactericidal nitrogen oxides was depressed in malnourished animals in the lungs specifically at early times (< 14 days) after infection. At later times, levels of expression became comparable to those in well-nourished controls, although the bacillary burden in the malnourished animals continued to rise. Nevertheless, urinary and serum nitrate contents, an index of total nitric oxide (NO) production in vivo, were not detectably diminished in malnourished, mycobacteria-infected mice. In contrast to the selective and early reduction of lymphokines and the inducible form of nitric oxide synthase in the lung, a marked diminution of the granulomatous reaction was observed in malnourished mice throughout the entire course of infection in all tissues examined (lungs, liver, and spleen). Remarkably, the progressively fatal course of tuberculosis observed in the malnourished mice could be reversed by restoring a full protein (20%) diet. The results indicate that protein calorie malnutrition selectively compromises several components of the cellular immune response that are important for containing and restricting tuberculous infection, and suggest that malnutrition-induced susceptibility to some infectious diseases can be reversed or ameliorated by nutritional intervention.

Molecular regulation of human interleukin 2 and T-cell function by interleukin 4

Distinct functional T-cell subsets, differing in the patterns of lymphokines produced, regulate cell-mediated and humoral immune responses. The two major types and their principal products, interleukin 4 and interferon gamma (IL-4 and IFN-gamma), are reciprocally negatively interactive. To analyze the molecular mechanism of IL-4-mediated suppression of cell-mediated immunity we studied its effects on expression of interleukin 2 (IL-2) and IFN-gamma. IL-4 pretreatment of Jurkat cells prior to stimulation resulted in a decrease in transcription of the IL2 gene. IL-4 suppressed IL-2 and IFN-gamma mRNA levels in primary human T cells, and addition of anti-CD28 antibodies relieved this suppression. Using enhancer-reporter constructs, IL-4 specifically down-regulated the NFIL-2B element. Electrophoretic mobility shift assays using a DNA oligomer containing the NFIL-2B binding site indicated that IL-4 inhibited the NFIL-2B complex and that the NFIL-2B DNA binding factor is distinct from AP-1. These results suggest that IL-4 may regulate development and function of T-cell subsets involved in cell-mediated immunity in part by inhibiting factors required for transcription of the IL2 gene.

Immunosuppressive roles for IL-10 and IL-4 in human infection. In vitro modulation of T cell responses in leprosy

IL-10 and IL-4 have been shown to exert an inhibitory effect on cell-mediated immune responses. Our previous studies of leprosy demonstrated that IL-10 and IL-4 mRNA were preferentially expressed in lesions from lepromatous patients, those immunologically unresponsive individuals that manifest widespread infection. To define more precisely the regulatory roles of these two cytokines in the immune response to infection, we studied in vitro responses to Mycobacterium leprae. M. leprae triggered IL-10 release from PBMC of patients and healthy donors; the predominant source of the IL-10 was found to be monocytes/macrophages. Stimulation of PBMC in the presence of neutralizing anti-IL-10 mAb indicated that endogenous IL-10 production inhibits PBMC proliferation and release of TNF-alpha, GM-CSF, and IFN-gamma. Paradoxically, studies using neutralizing anti-IL-4 mAb indicated that endogenous IL-4 production enhances PBMC proliferative responses most strikingly in lepromatous patients. We found that rIL-4 expanded CD8+ T cells from lepromatous patients in vitro. CD8+ T cells from lepromatous patients have been shown to suppress CD4+ T cell responses, in part by the release of IL-4. Our study indicated that endogenous IL-4 production inhibited IL-10 secretion and, concomitantly, increased TNF-alpha and GM-CSF release. The present data suggest that, on balance, IL-4 and IL-10 contribute to immunosuppression in human infectious disease.

Immunosuppressive roles for IL-10 and IL-4 in human infection. In vitro modulation of T cell responses in leprosy

IL-10 and IL-4 have been shown to exert an inhibitory effect on cell-mediated immune responses. Our previous studies of leprosy demonstrated that IL-10 and IL-4 mRNA were preferentially expressed in lesions from lepromatous patients, those immunologically unresponsive individuals that manifest widespread infection. To define more precisely the regulatory roles of these two cytokines in the immune response to infection, we studied in vitro responses to Mycobacterium leprae. M. leprae triggered IL-10 release from PBMC of patients and healthy donors; the predominant source of the IL-10 was found to be monocytes/macrophages. Stimulation of PBMC in the presence of neutralizing anti-IL-10 mAb indicated that endogenous IL-10 production inhibits PBMC proliferation and release of TNF-alpha, GM-CSF, and IFN-gamma. Paradoxically, studies using neutralizing anti-IL-4 mAb indicated that endogenous IL-4 production enhances PBMC proliferative responses most strikingly in lepromatous patients. We found that rIL-4 expanded CD8+ T cells from lepromatous patients in vitro. CD8+ T cells from lepromatous patients have been shown to suppress CD4+ T cell responses, in part by the release of IL-4. Our study indicated that endogenous IL-4 production inhibited IL-10 secretion and, concomitantly, increased TNF-alpha and GM-CSF release. The present data suggest that, on balance, IL-4 and IL-10 contribute to immunosuppression in human infectious disease.

Revisiting and revising suppressor T cells

A great deal of experimental evidence supports the phenomenon of immunological suppression. The molecular mechanisms to explain the phenomenology have, however, remained controversial. In this review, the data are reinterpreted in light of the recent advances in the understanding of T-cell subsets, the cross-regulatory properties of lymphokines and the differential presentation capacities of different antigen-presenting cell types.

Stigma variations: observations on suppressor T cells and leprosy

Few areas of immunology have been so controversial as that of suppressor T cells. Studies of T cell clones derived from patients with infectious diseases, including leprosy, and allergies have allowed the delineation of functional human T cell subsets. Both CD4 and CD8 cells can be discriminated into subsets that are differentiated by their functions and patterns of lymphokines. Type 1 CD4 cells reactive with lepromin and PPD produce IFN-gamma and IL-2 predominantly, while Type 2 CD4 clones, specific for tetanus toxoid, produce IL-4 and IL-5. Type 1 CD8 cytotoxic T lymphocytes produce predominantly IFN-gamma and IL-2. T suppressor clones derived from immunologically unresponsive lepromatous leprosy patients are antigen-specific, CD8 cells, HLA-DQ restricted, and produce predominantly IL-4, and were designated Type 2 CD8 cells. Several models for peripheral tolerance based on distinct functional T cell subsets are discussed. Previous models of T cell suppression in the mouse and the reciprocal relationship between humoral and cell-mediated immunity in general are reinterpreted in light of such T cell subset interactions.

Expression of adhesion molecules in leprosy lesions

Leprosy presents as a clinical spectrum that is precisely paralleled by a spectrum of immunological reactivity. The disease provides a useful and accessible model, in this case in the skin, in which to study the dynamics of cellular immune responses to an infectious pathogen, including the role of adhesion molecules in those responses. In lesions characterized by strong delayed-type hypersensitivity against Mycobacterium leprae (tuberculoid, reversal reaction, and Mitsuda reaction), the overlying epidermis exhibited pronounced keratinocyte intracellular adhesion molecule 1 (ICAM-1) expression and contained lymphocytes expressing the ICAM-1 ligand, LFA-1. Conversely, in lesions in which delayed-type hypersensitivity was lacking (lepromatous), keratinocyte ICAM-1 expression was low and LFA-1+ lymphocytes were rare. Expression of these adhesion molecules on the cells within the dermal granulomas was equivalent throughout the spectrum of leprosy. The percentage of lymphocytes in these granulomas containing mRNA coding for gamma interferon and tumor necrosis factor alpha, synergistic regulators of ICAM-1 expression, paralleled epidermal ICAM-1 expression. In lesions of erythema nodosum leprosum, a reactional state of lepromatous leprosy thought to be due to immune complex deposition, keratinocyte ICAM-1 expression and gamma interferon mRNA+ cells were both prominent. Antibodies to LFA-1 and ICAM-1 blocked the response of both alpha beta and gamma delta T-cell clones in vitro to mycobacteria. Overall, the expression of adhesion molecules by immunocompetent epidermal cells, as well as the cytokines which regulate such expression, correlates with the outcome of the host response to infection.

Differing lymphokine profiles of functional subsets of human CD4 and CD8 T cell clones

Functional subsets of human T cells were delineated by analyzing patterns of lymphokines produced by clones from individuals with leprosy and by T cell clones of known function. CD4 clones from individuals with strong cell-mediated immunity produced predominantly interferon-gamma, whereas those clones that enhanced antibody formation produced interleukin-4. CD8 cytotoxic T cells secreted interferon-gamma. Interleukin-4 was produced by CD8 T suppressor clones from immunologically unresponsive individuals with leprosy and was found to be necessary for suppression in vitro. Both the classic reciprocal relation between antibody formation and cell-mediated immunity and resistance or susceptibility to certain infections may be explained by T cell subsets differing in patterns of lymphokine production.

Differing lymphokine profiles of functional subsets of human CD4 and CD8 T cell clones

Functional subsets of human T cells were delineated by analyzing patterns of lymphokines produced by clones from individuals with leprosy and by T cell clones of known function. CD4 clones from individuals with strong cell-mediated immunity produced predominantly interferon-gamma, whereas those clones that enhanced antibody formation produced interleukin-4. CD8 cytotoxic T cells secreted interferon-gamma. Interleukin-4 was produced by CD8 T suppressor clones from immunologically unresponsive individuals with leprosy and was found to be necessary for suppression in vitro. Both the classic reciprocal relation between antibody formation and cell-mediated immunity and resistance or susceptibility to certain infections may be explained by T cell subsets differing in patterns of lymphokine production.

Immunological suppression by human CD8+ T cells is receptor dependent and HLA-DQ restricted

Mechanisms of specific immunologic unresponsiveness or tolerance and their regulation by the major histocompatibility complex remain central issues in immunology. Recent findings that potentially reactive anti-self T cells are not completely clonally deleted in the thymus and that specific immunological unresponsiveness can be acquired in certain infectious diseases, such as leprosy, suggest that peripheral unresponsiveness can be developed and maintained in adults. Human antigen-specific T suppressor cells represent one mechanism of peripheral tolerance. Clones of CD8+ T suppressor cells have been derived from blood or lesions of patients with lepromatous leprosy who are selectively unable to mount cellular immunity to Mycobacterium leprae. Using a panel of M. leprae-specific CD4+ and CD8+ T-cell clones of differing major histocompatibility complex class II haplotypes, suppression in vitro was found to be restricted by HLA-DQ and not by HLA-DR and inhibited by antibodies to HLA-DQ. In addition, antigen-induced suppression could be inhibited by antibodies specific to appropriate polymorphic T-cell receptor beta chains of the CD8+ clones. The results establish that activation of specific T suppressor cells is dependent on their polymorphic T-cell receptors and suggest that HLA-DQ serves as the preferred restricting element for suppression.

CD2 expression and function in lepromatous leprosy

Leprosy is a spectral disease in which clinical presentation is thought to be related to the host immune response. Previous investigations have suggested that selective unresponsiveness to Mycobacterium leprae in patients with lepromatous leprosy is due to the presence of M. leprae-specific T-suppressor cells. However, it has recently been suggested that CD2 modulation was the mechanism for the observed impaired immune response in lepromatous patients. Therefore, we studied the expression of CD2 and CD3 on lymphocytes in lepromatous skin lesions and peripheral blood mononuclear cells (PBMC). Using immunohistochemical techniques, we found that virtually all of the CD3+ cells in leprosy skin lesions expressed CD2. In addition, indirect immunofluorescence flow cytometry demonstrated that most CD3+ cells in the peripheral blood possessed the CD2 marker, suggesting that CD2 expression of T-lymphocytes is normal. T-cell activation using paired anti-T11(2) and anti-T11(3) or anti-CD3 monoclonal antibodies demonstrated similar 3H-thymidine incorporation and gamma interferon production in the PBMC of lepromatous patients in comparison with the PBMC of their contacts and tuberculoid patients. However, lepromatous PBMC did not proliferate or produce gamma interferon in response to M. leprae. Our data suggest not only that CD2 expression is normal on T lymphocytes in lepromatous leprosy skin lesions but also that CD2 expression in peripheral blood lymphocytes is functional in T-cell activation. Defective CD2 modulation does not appear to be the mechanism for specific unresponsiveness in lepromatous leprosy.

Characterization of Mycobacterium leprae cell wall-associated proteins with the use of T lymphocyte clones

Development of a vaccine against leprosy depends on the identification of Ag that stimulate cell-mediated immune responses. We have previously demonstrated that cell wall proteins of Mycobacterium leprae are highly immunogenic. By using human cell wall-specific T cell clones we have begun to characterize soluble proteins that integrate into the cell wall skeleton. T cells from leprosy lesions were expanded with IL-2 in vitro yet retained specificity to Ag of the insoluble cell wall core (CWC) in vitro, indicating that T cells had been activated by CWC Ag in vivo. A cell wall protein-peptidoglycan complex and cell wall protein preparations lacking carbohydrates and lipids from CWC retained T cell reactivity. To identify immunogenic protein component(s) of cell wall protein, T cell lines were established to cell walls and tested against M. leprae proteins separated by SDS-PAGE and transferred to nitrocellulose. Greatest T cell reactivity was observed to proteins of Mr 7 kDa, 16 kDa, and 28 kDa. T cell clones reactive with 7-kDa and 16-kDa Ag from gels failed to respond to proteins of other Mr separated under either reducing or nonreducing conditions, indicating that these molecules are not subunits of larger proteins and may represent monomeric units polymerized into cell walls. The approaches described herein for characterization of immunodominant T cell Ag of M. leprae may be useful for study of T cell Ag in cell walls of bacterial pathogens of man.

Characterization of Mycobacterium leprae cell wall-associated proteins with the use of T lymphocyte clones

Development of a vaccine against leprosy depends on the identification of Ag that stimulate cell-mediated immune responses. We have previously demonstrated that cell wall proteins of Mycobacterium leprae are highly immunogenic. By using human cell wall-specific T cell clones we have begun to characterize soluble proteins that integrate into the cell wall skeleton. T cells from leprosy lesions were expanded with IL-2 in vitro yet retained specificity to Ag of the insoluble cell wall core (CWC) in vitro, indicating that T cells had been activated by CWC Ag in vivo. A cell wall protein-peptidoglycan complex and cell wall protein preparations lacking carbohydrates and lipids from CWC retained T cell reactivity. To identify immunogenic protein component(s) of cell wall protein, T cell lines were established to cell walls and tested against M. leprae proteins separated by SDS-PAGE and transferred to nitrocellulose. Greatest T cell reactivity was observed to proteins of Mr 7 kDa, 16 kDa, and 28 kDa. T cell clones reactive with 7-kDa and 16-kDa Ag from gels failed to respond to proteins of other Mr separated under either reducing or nonreducing conditions, indicating that these molecules are not subunits of larger proteins and may represent monomeric units polymerized into cell walls. The approaches described herein for characterization of immunodominant T cell Ag of M. leprae may be useful for study of T cell Ag in cell walls of bacterial pathogens of man.

On the mechanism of human T cell suppression

Previous evidence from several laboratories suggests that CD8+ T suppressor cells may be important regulatory elements governing specific unresponsiveness of lepromatous lepromatous leprosy patients to M.leprae. To analyse the mechanism of suppression, CD8+ Ts clones were established from lesions and peripheral blood of lepromatous patients and tested for ability to suppress antigen-responsive CD4+. Th clones or PBL. Suppression required induction by specific M.leprae antigen, but was effected in an antigen-non-specific fashion. The Ts clones failed to exhibit cytotoxicity of four antigen-exposed MHC-matched target cells: (i) an ori-SV40 transformed macrophage line; (ii) EBV transformed B cell lines; (iii) primary macrophages; and (iv) M.leprae responsive CD4+ cells. The possibility that Ts clones induce functional inactivation of CD4+ clones in vitro was investigated. M.leprae-responsive CD4+ clones were preincubated with Ts CD8+ clones, APC, and antigen for 16 h, after which the CD8+ cells were removed. The CD4+ clones with M.leprae and APC remained unresponsive to restimulation with APC and antigen for at least 10 days, although they responded to IL-2. Addition of IL-2 to the pre- or post-incubation cultures neither prevented the induction of unresponsiveness, nor reversed it. Earlier models of tolerance have suggested that receptor occupancy in the absence of second signals induces tolerance in B and T cells. Under conditions in which antigen responses of Th clones were HLA-DR-restricted, the Ts clones were able to suppress the response of DR mismatched Th clones. Thus, the effect of the Ts cells, like mechanisms requiring antigen presentation without a second signal, appears to be induction of clonal anergy in Th cells, perhaps by a novel mechanism.

Immunological significance of Mycobacterium leprae cell walls

Cell walls of Mycobacterium leprae, prepared by differential solvent extraction, were shown to contain arabinogalactan, mycolates, and peptidoglycan. In addition, amino acid analysis revealed the unexpected presence of large amounts of protein that retained potent immunological reactivity. Purified cell walls stimulated proliferation of T cells from tuberculoid, but not from lepromatous leprosy, patients and elicited delayed-type hypersensitivity skin reactions in guinea pigs and patients sensitized to M. leprae. Analysis of the precursor frequency of antigen-reactive human peripheral T cells revealed that as many cells (approximately equal to 1/6000) proliferate to antigen contained in cell walls as to intact M. leprae. Sequential removal of mycolates and arabinogalactan resulted in a large peptidoglycan-protein complex that retained all the immunological activity. This immunological reactivity and the inherent protein were destroyed by proteolysis. Thus, cell wall protein is a major contributor to cell-mediated immune reactivity to this pathogenic mycobacterium.