Immunoglobulin G, A, and M responses in serum and circulating immune complexes elicited by the 16-kilodalton antigen of Mycobacterium tuberculosis

The 16-kDa cytosolic antigen of M. tuberculosis was purified to homogeneity by molecular sieving chromatography, and the diagnostic potential of the antigen was evaluated in various categories of patients by enzyme-linked immunosorbent assay (ELISA). The immunoglobulin G (IgG), IgA, and IgM antibody levels to 16-kDa antigen were estimated in the two polar groups, namely, smear- and culture-positive pulmonary tuberculosis (S(+)C(+)) patients and healthy subjects (HS). Sensitivities of 62, 52 and 11% with specificities of 100, 97, and 95% were obtained for the three isotypes, respectively. The total number of positives by a combination of the three isotypes was analyzed in the polar groups, and the sensitivity improved to 83% with a specificity of 93%. Even when a combination of IgG and IgA alone was considered, the sensitivity was 82% with a specificity of 97%. Polyethylene glycol precipitation of the circulating immune complex (CIC) in sera was carried out. The CIC-bound antibodies to 16-kDa antigen were assessed by ELISA in the S(+)C(+), S(-)C(+), and S(-)C(-) categories of patients. Measuring the IgG-IgA-IgM combination positivities of the CIC-bound antibodies gave sensitivities of 97.5, 100, and 45.3%, respectively. The specificity of the assay with these combinations was maintained at 95.4%.

Heat shock proteins 70 and 60 share common receptors which are expressed on human monocyte-derived but not epidermal dendritic cells

Priming of CTL by means of heat shock proteins (hsp) is dependent on antigen-presenting cells (APC), which present the hsp-associated peptides, via their cell surface MHC class I molecules, toCD8(+) T cells. It has not yet been established how human (hu) hsp70 interacts with the major (hu)APC, the dendritic cells (DC). Here we show that (hu)hsp70 is specifically internalized intoCD14(-), Toll-like receptor 4(-) monocyte-derived (hu)DC by receptor-mediated endocytosis. We further demonstrate that (hu)hsp70 and (hu)hsp60 share the same receptors on (hu)monocyte-derived DC. Both molecules as well as MHC class I molecules are spontaneously internalized and reach the MHC class II-enriched compartments. Finally, freshly isolated (hu) epidermal Langerhans cells (LC), the DC of the skin, as well as CD34(+)-derived LC do not bind hsp60 or hsp70. Given the likely importance of the internalization of hsp70 by APC in the induction of the immune responses, the finding that hsp60 and hsp70 are internalized through the same receptor(s) may explain why microbial hsp60 represents a major T cell antigen. This may rationalize the use of microbial hsp60 to prime immune responses against microbes. The lack of hsp60/70 receptors on epidermal LC raises the crucial question as to whether absence of priming of the skin and mucosal immune systems by hsp-polypeptide complexes could account for some tissue-specific diseases. This work also points to a potential advantage of using monocyte-derived DC in human immunotherapeutic applications of hsp60/70.

Identification of the 49-kDa autoantigen associated with lymphocytic hypophysitis as alpha-enolase

Lymphocytic hypophysitis is part of the spectrum of organ-specific autoimmune diseases, and although its histopathology is well documented, its pathogenesis is unclear. Serum autoantibodies directed against a 49-kDa cytosolic protein are detected by immunoblotting in 70% of patients with biopsy-proven lymphocytic hypophysitis. Here we report the purification and identification of this first target autoantigen in lymphocytic hypophysitis. The autoantigen has a molecular mass of 49 kDa, a cytosolic localization, and a ubiquitous tissue distribution. The 49-kDa protein was purified from monkey brain and human placental cytosol. Limited amino acid sequencing after proteolytic digestion of the human placental protein showed identity with alpha-enolase. The identification was confirmed using sera from patients with pituitary autoimmunity, which strongly reacted with recombinant human alpha-enolase and yeast enolase, but not with rabbit muscle beta- enolase. This indicates that the immunoreactive epitopes are largely conserved from yeast to human, but are not present in beta-enolase. alpha-Enolase autoantibodies are not specific to pituitary autoimmune disease and have been reported in other autoimmune diseases. However, this study is the first to indicate a role for alpha-enolase as an autoantigen in lymphocytic hypophysitis.

Single-chain antibody against the common epitope of mutant p53: isolation and intracytosolic expression in mammalian cells

The peptide epitope FRHSVV is cryptic in wild-type p53 and is exposed in many types of mutant p53 molecules isolated from various tumors. Mutant p53 marked by this epitope abrogates a tumor-suppressor function of wild-type p53 and possibly contributes to the transforming potential of other oncogenic processes. We report here the construction of a single-chain scFv antibody gene library derived from the mRNA of a mouse immunized with the epitope peptide FRHSVV which mimics the common epitope in p53 mutant protein molecules. The scFv was presented by phage display. The selected antibody gene, named ME1, was found to bind to the mutant p53 protein but not to the wild-type p53 protein. Preliminary studies show that the ME1 gene is expressed in the cytosol of mammalian cells. These findings suggest that the ME1 single-chain antibody may be useful as a tool for clarifying the role of mutant p53 in tumor transformation, especially in cells heterozygous in p53, and possibly for gene therapy of tumors.

Serologic response to a secreted and a cytosolic antigen of Mycobacterium tuberculosis in childhood tuberculosis

BACKGROUND AND AIM

Bacteriologic diagnosis of childhood tuberculosis is difficult, and alternate methods are needed. The utility of a serologic test for major secretory antigen (30 kDa) and a cytosolic antigen (16 kDa) of Mycobacterium tuberculosis was evaluated for the diagnosis of tuberculosis in children.

METHODS

Enzyme-linked immunosorbent assay was used. Specific IgG, IgA and IgM antibodies were measured in the sera from 26 clinically and/or bacteriologically diagnosed cases of childhood tuberculosis and 61 normal children.

RESULTS

Anti-IgG antibodies alone, against both 30- and 16-kDa antigens, were detected in 65.4% of patients. However, by combination of all three isotypes, increased sensitivities of 84.6 and 73%, with a specificity of 96.7% each, were obtained for 30- and 16-kDa antigens, respectively.

CONCLUSIONS

We found good specificity and reasonably good sensitivity for detection of antibodies by enzyme-linked immunosorbent assay to 30-kDa antigen alone. The 16-kDa antigen did not perform as well.

Orally administered Giardia duodenalis extracts enhance an antigen-specific antibody response

We have identified novel adjuvant activity in specific cytosol fractions from trophozoites of Giardia isolate BRIS/95/HEPU/2041 (J. A. Upcroft, P. A. McDonnell, and P. Upcroft, Parasitol. Today, 14:281-284, 1998). Adjuvant activity was demonstrated in the systemic and mucosal compartments when Giardia extract was coadministered orally with antigen to mice. Enhanced antigen-specific serum antibody responses were demonstrated by enzyme-linked immunosorbent assay to be comparable to those generated by the "gold standard," mucosal adjuvant cholera toxin. A source of adjuvant activity was localized to the cytosolic component of the parasite. Fractionation of the cytosol produced fraction pools, some of which, when coadministered with antigen, stimulated an enhanced antigen-specific serum response. The toxic component of conventional mucosal adjuvants is associated with adjuvant activity; therefore, in a similar way, the toxin-like attributes of BRIS/95/HEPU/2041 may be responsible for its adjuvanticity. Complete characterization of the adjuvant is under way.

Autoantibodies to human cytosol: a marker of sporadic porphyria cutanea tarda

The enzymes potentially involved in the pathogenesis of sporadic porphyria cutanea tarda (PCT) reside in liver cytosoles and microsomes. PCT is frequently associated with hepatitis C virus (HCV) infection, which is in turn associated with autoimmune manifestations. To investigate whether autoimmune reactions, possibly triggered by HCV, are involved in the pathogenesis of PCT, we measured by immunoblot autoantibodies to human cytosolic and microsomal liver fractions in 82 patients with PCT (77% with HCV infection), 105 with other liver disorders and 40 healthy subjects. Anti-liver cytosolic antibodies were more frequent in PCT patients (38/82, 46%) than in pathological controls (P < 0.05-P < 0.001) or in healthy subjects (3/40, 8%, P < 0.001). Among PCT patients, anticytosolic antibodies were more frequent in HCV positive (36/63, 57%) than in HCV negative (2/19, 11%, P < 0.05) cases. Reactivity to a 40-kDa cytosolic polypeptide was present in 20 PCT patients (19 HCV positive), being more frequent than in all pathological controls (P < 0.01-P < 0.0001). Histological activity index (P = 0.04) and antibodies to HCV (P = 0.027) - but not HCV RNA - were associated independently with anticytosolic antibodies as assessed by multivariate analysis. In contrast, frequency of antiliver microsomal antibodies was similar in PCT patients (24/82, 29%) and pathological controls (8-26%), being higher in the autoimmune hepatitis control group (23/23, 100%, P < 0.0001). In conclusion, anticytosolic antibodies, particularly to a 40-kDa polypeptide, are frequent in PCT and associated with HCV infection and severity of liver damage.

Vaccination with cytoplasmic ErbB-2 DNA protects mice from mammary tumor growth without anti-ErbB-2 antibody

Wild-type ErbB-2 (E2) positive D2F2/E2 tumors are rejected by active vaccination with ErbB-2 DNA. However, anti-ErbB-2 Ab response can cause cardiac toxicity or interfere with cellular immunity. It will be advantageous to induce only cellular immunity by active vaccination. A panel of E2 DNA vaccines were constructed, and their vaccination efficacy was ranked as E2 > tyrosine kinase-deficient ErbB-2 (E2A) > full-length ErbB-2 targeted to the cytoplasm (cytE2) > tyrosine kinase-deficient cytE2 (cytE2A). E2A is a tyrosine kinase-deficient mutant containing a single residue substitution. CytE2 or cytE2A encodes a full-length protein that is targeted to and rapidly degraded in the cytosol by the proteasomes. Covaccination with cytE2A and GM-CSF or IL-2 DNA resulted in equivalent anti-tumor activity as E2. However, anti-ErbB-2 Ab was induced by E2 or E2A, but not cytE2 or cytE2A. Therefore, cytE2A appears to induce anti-tumor immunity without an Ab response. ErbB-2-specific CTL were detected in mice immunized with cytE2A and GM-CSF and have rejected tumor challenge. Depletion of CD8, but not CD4 T cells reduced anti-tumor immunity, indicating CTL as the effector cells. Covaccination with E2A and cytE2A induced synergistic anti-tumor activity, supporting enhanced peptide presentation from cytE2A, which was further evidenced by superior CTL activation using APCs expressing cytE2 vs E2. Taken together, cytoplasmic ErbB-2 DNA induced anti-tumor CTL, but not humoral response, demonstrating the feasibility of eliciting individual effector mechanism by targeted DNA vaccine.

Efficient presentation of both cytosolic and endogenous transmembrane protein antigens on MHC class II is dependent on cytoplasmic proteolysis

Peptides from extracellular proteins presented on MHC class II are mostly generated and loaded in endolysosomal compartments, but the major pathways responsible for loading peptides from APC-endogenous sources on MHC class II are as yet unclear. In this study, we show that MHC class II molecules present peptides from proteins such as OVA or conalbumin introduced into the cytoplasm by hyperosmotic pinosome lysis, with efficiencies comparable to their presentation via extracellular fluid-phase endocytosis. This cytosolic presentation pathway is sensitive to proteasomal inhibitors, whereas the presentation of exogenous Ags taken up by endocytosis is not. Inhibitors of nonproteasomal cytosolic proteases can also inhibit MHC class II-restricted presentation of cytosolically delivered protein, without inhibiting MHC class I-restricted presentation from the same protein. Cytosolic processing of a soluble fusion protein containing the peptide epitope I-Ealpha(52-68) yields an epitope that is similar to the one generated during constitutive presentation of I-Ealpha as an endogenous transmembrane protein, but is subtly different from the one generated in the exogenous pathway. Constitutive MHC class II-mediated presentation of the endogenous transmembrane protein I-Ealpha is also specifically inhibited over time by inhibitors of cytosolic proteolysis. Thus, Ag processing in the cytoplasm appears to be essential for the efficient presentation of endogenous proteins, even transmembrane ones, on MHC class II, and the proteolytic pathways involved may differ from those used for MHC class I-mediated presentation.

Distinct epitopes on formiminotransferase cyclodeaminase induce autoimmune liver cytosol antibody type 1

Liver cytosol antibody type 1 (LC1) is regarded as a serologic marker of type 2 autoimmune hepatitis, in addition to liver kidney microsomal antibody type 1. Among 38 patients with type 2 autoimmune hepatitis, 23 were positive for LC1 antibodies. The antigen recognized by LC1 has been identified as a liver-specific 58-kd metabolic enzyme named formiminotransferase cyclodeaminase (FTCD). All 23 LC1-positive sera immunoprecipitated rat FTCD, and 22 gave an identity reaction with rat FTCD by immunodiffusion. No reaction was observed with sera from 10 patients with type 1 autoimmune hepatitis, 10 with primary biliary cirrhosis, 10 with chronic hepatitis C, and 10 healthy controls. By Western immunoblotting all 23 LC1-positive sera and all the controls tested negative, suggesting that all the antigenic epitopes were destroyed by denaturation. FTCD is a bifunctional protein composed of distinct globular FT and CD domains connected by a short linker. To identify epitopes that trigger the LC1 autoimmune response, we tested LC1 antibodies against FTCD constructs encoding the N-terminal FT domain (amino acids 1-339), or the C-terminal CD domain (amino acids 332-541). Of 20 sera positive against full-length FTCD, 8 (40%) recognized the FT domain and the CD domain, 7 (35%) recognized only the FT domain, and 5 (25%) did not recognize either construct. No sera reacted with only the CD domain. These data indicate that multiple regions of FTCD trigger the LC1 autoimmune response, and that LC1 reactivity is mainly directed to conformation-sensitive epitopes located in the FT region of FTCD.

Neutrophils process exogenous bacteria via an alternate class I MHC processing pathway for presentation of peptides to T lymphocytes

Peptides that are presented by class I MHC (MHC-I) molecules derive from cytosolic Ags processed via the conventional MHC-I pathway or exogenous Ags processed via alternate MHC-I processing mechanisms. Alternate MHC-I processing by macrophages and dendritic cells allows presentation of peptides from particulate Ags, including bacteria. Despite the established phagocytic activity of neutrophils, MHC-I processing and presentation of phagocytosed Ags by neutrophils has not been investigated. Murine neutrophils from peritoneal exudates were shown to express MHC-I molecules and tested for the ability to process HB101.Crl-OVA, Escherichia coli transfected to express a fusion protein containing the 257-264 epitope of OVA. Neutrophils were found to process HB101.Crl-OVA and present OVA(257-264)-K(b) complexes to CD8OVA T hybridoma cells via a pathway that was resistant to brefeldin A, an inhibitor of anterograde endoplasmic reticulum-Golgi transport, and lactacystin, a proteasome inhibitor. These results suggest that neutrophils process phagocytosed bacteria via a vacuolar alternate MHC-I pathway that does not involve cytosolic processing. In addition, neutrophils were found to secrete or "regurgitate" processed peptide that was subsequently presented by neighboring prefixed macrophages or dendritic cells. Thus, neutrophils may influence T cell responses to bacteria, either by directly presenting peptide-MHC-I complexes or by delivering peptides to other APCs for presentation. Hypothetically, neutrophils may directly present peptide to effector T cells in vivo at sites of inflammation, inducing cytokine production, whereas dendritic cells in receipt of neutrophil-derived antigenic peptides may migrate to lymphoid organs to initiate T cell responses.

Protection against murine listeriosis by oral vaccination with recombinant Salmonella expressing hybrid Yersinia type III proteins

In the present study, we have investigated the possibility to engage the Yersinia outer protein E (YopE) as a carrier molecule for heterologous Ag delivery by the type III secretion system of Salmonella typhimurium. Defined secretion and translocation domains of YopE were fused to the immunodominant T cell Ags listeriolysin O and p60 of Listeria monocytogenes. In vitro experiments showed that S. typhimurium allows secretion and translocation of large hybrid YopE proteins in a type III-dependent fashion. Translocation and cytosolic delivery of these chimeric proteins into host cells, but not secretion into endosomal compartments, led to efficient MHC class I-restricted Ag presentation of listerial nonamer peptides. Mice orally vaccinated with a single dose of attenuated S. typhimurium expressing translocated hybrid YopE proteins revealed high numbers of IFN-gamma-producing cells reactive with listeriolysin O 91-99 or p60 217-225, respectively. This CD8 T cell response protected mice against a challenge with L. monocytogenes. In conclusion, these findings suggest that YopE is a versatile carrier molecule for type III-mediated foreign Ag delivery by Salmonella vaccine strains.

Cytosolic phospholipase A2 participates with TNF-alpha in the induction of apoptosis of human macrophages infected with Mycobacterium tuberculosis H37Ra

Macrophage (MPhi) apoptosis, an important innate microbial defense mechanism induced by Mycobacterium tuberculosis (Mtb) H37Ra, depends on the induction of TNF-alpha synthesis. When protein synthesis is blocked, both infection with Mtb and addition of TNF-alpha are required to induce caspase 9 activation, caspase 3 activation and apoptosis. In this study, we show that the second protein synthesis-independent signal involves activation of group IV cytosolic phospholipase A2 (cPLA2). Apoptosis of Mtb-infected MPhi and concomitant arachidonic acid release are abrogated by group IV cPLA2 inhibitors (methyl arachidonyl fluorophosphate and methyl trifluoromethyl ketone), but not by inhibitors of group VI Ca2+-independent (iPLA2; bromoenol lactone) or of secretory low molecular mass PLA2. In MPhi homogenates, the predominant PLA2 activity showed the same inhibitor sensitivity pattern and preferred arachidonic acid over palmitic acid in substrates, also indicating the presence of one or more group IV cPLA2 enzymes. In concordance with these findings, MPhi lysates contained transcripts and protein for group IV cPLA2-alpha and cPLA2-gamma. Importantly, group IV cPLA2 inhibitors significantly reduced MPhi antimycobacterial activity and addition of arachidonic acid, the major product of group IV cPLA2, to infected MPhi treated with cPLA2 inhibitors completely restored the antimycobacterial activity. Importantly, addition of arachidonic acid alone to infected MPhi significantly reduced the mycobacterial burden. These findings indicate that Mtb induces MPhi apoptosis by independent signaling through at least two pathways, TNF-alpha and cPLA2, which are both also critical for antimycobacterial defense of the MPhi.

Heat shock protein-chaperoned peptides but not free peptides introduced into the cytosol are presented efficiently by major histocompatibility complex I molecules

The studies reported here bear on the events in the cytosol that lead to trafficking of peptides during antigen processing and presentation by major histocompatibility complex (MHC) I molecules. We have introduced free antigenic peptides or antigenic peptides bound to serum albumin or to cytosolic heat shock proteins hsp90 (and its endoplasmic reticular homologue gp96) or hsp70 into the cytosol of living cells and have monitored the presentation of the peptides by appropriate MHC I molecules. The experiments show that (i) free peptides or serum albumin-bound peptides, introduced into the cytosol, become ligands of MHC I molecules at a far lower efficiency than peptides chaperoned by any of the heat shock proteins tested and (ii) treatment of cells with deoxyspergualin, a drug that binds hsp70 and hsp90 with apparent specificity, abrogates the ability of cells to present antigenic peptides through MHC I molecules, and introduction of additional hsp70 into the cytosol overcomes this abrogation. These results suggest for the first time a functional role for cytosolic chaperones in antigen processing.

Intracellular Antibody Neutralizes Listeria Growth

We previously reported that treatment of mice with a neutralizing mAb against listeriolysin O (LLO), the pore-forming toxin of Listeria monocytogenes, provided resistance to this intracellular bacterium. We evaluated whether anti-LLO mAb would affect Listeria handling by macrophages, essential cells in Listeria resistance. Macrophages infected in the presence of anti-LLO mAb showed a marked reduction in intracellular Listeria growth, with a concomitant block in LLO-dependent Listeria passage from phagosome to cytosol. Anti-LLO mAb did not opsonize Listeria but, rather, acted within macrophages to neutralize LLO. Importantly, anti-LLO mAb effects on Listeria growth were independent of Fcgamma receptor expression, IFNgamma signaling, and production of nitric oxide and superoxide. These results identify a novel mechanism for antibody control of bacteria within macrophages.

Anthrax-toxin-mediated delivery of a 19 kDa antigen of Mycobacterium tuberculosis into the cytosol of mammalian cells

PA63, the proteolytically activated 63 kDa fragment of protective antigen (PA, 83 kDa), mediates translocation of lethal factor (LF) and oedema factor into the cytosol. The N-terminal 254 amino acids of LF (LFn) are required for binding to PA63 and mediating translocation of active ligands fused to either the N- or C-terminus. Here we report translocation of a 19 kDa antigen of Mycobacterium tuberculosis into the cytosol of mammalian cells when fused to the C-terminus of LFn (LFn-19kDa). The fusion protein was non-toxic to J774A.1 macrophage cells in combination with PA and retained the ability to bind to PA63 when incubated with Chinese hamster ovary K1 cells. The data show the efficacy of anthrax toxin to mediate translocation of M. tuberculosis antigens into the cytosol of mammalian cells and may prove useful in delivering proteins and peptides carrying immunodominant mycobacterial antigens into the cytosol.

Critical requirement for the membrane-proximal cytosolic tyrosine residue for CD28-mediated costimulation in vivo

The YMNM motif that exists in the CD28 cytoplasmic domain is known as a binding site for phosphatidylinositol 3-kinase and Grb-2 and is considered to be important for CD28-mediated costimulation. To address the role of the YMNM motif in CD28 cosignaling in primary T cells, we generated transgenic mice on a CD28 null background that express a CD28 mutant lacking binding ability to phosphatidylinositol 3-kinase and Grb-2. After anti-CD3 and anti-CD28 Ab stimulation in vitro, the initial proliferative response and IL-2 secretion in CD28 Y189F transgenic T cells were severely compromised, while later responses were intact. In contrast to anti-CD3 and anti-CD28 Ab stimulation, PMA and anti-CD28 Ab stimulation failed to induce IL-2 production from CD28 Y189F transgenic T cells at any time point. Using the graft-vs-host reaction system, we assessed the role of the YMNM motif for CD28-mediated costimulation in vivo and found that CD28 Y189F transgenic spleen cells failed to engraft and could not induce acute graft-vs-host reaction. Together, these results suggest that the membrane-proximal tyrosine of CD28 is required for costimulation in vivo. Furthermore, these results indicate that the results from in vitro assays of CD28-mediated costimulation may not always correlate with T cell activation in vivo.

Ku autoantigen (DNA helicase) is required for interleukins-13/-4-induction of 15-lipoxygenase-1 gene expression in human epithelial cells

As reported previously in human monocytes, a human lung epithelial cell line, A549, showed de novo induction of 15-Lipoxygenase-1 (15-LO-1) in response to interleukins-13 (IL-13) and -4 (IL-4). In this cell line, 15-LO-1 expression, by RT-PCR and western blotting, was observed following 6 and 24 h of exposure to human IL-13 (ED50 5 ng/ml) and IL-4 (ED50 0.2 ng/ml). We have previously shown that no cis-acting regulatory elements exist within the 15-LO-1 promoter region. To define IL-13 and IL-4 responsive trans-acting elements, we identified a region (DP2: -353 to -304 bp site) within the 15-LO-1 promoter (by footprinting experiments) to which IL-13-responsive elements (or factors) bind specifically (Kelavkar et al, 1998, Mol Biol Rep 25, 173-182). To further delineate this region, we constructed (by site-directed mutagenesis) several deletion mutants in the 'LOPB5' region containing the 29 bp within the -353 to -304 bp of the DP2 core element. These were: DP3 (site totally deleted), DP4 (5 bp deleted at the center of the site), DP5 (8 bp at the 5'-end of the site) and DP6 (13 bp at the 3'-end of the site). Cotransfection of these deletion constructs (driving luciferase reporter genes) was associated with 90% (DP4, DP5 and DP6) or 100% (DP3) abrogation of promoter activity at 24 h. Purification of nuclear protein extracts from IL-13 and IL-4-stimulated A549 cells, using a DP2 core containing affinity column, identified a 150 kDa protein under non-denaturing conditions, and two, 70 and 85 kDa proteins under denaturing conditions. These were not detectable by Coomassie blue staining in control nuclear protein extracts. Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) of the tryptic digests of these proteins, identified one as the 86 kDA Lupus KU autoantigen protein P86 and the second as the 70 kDa Lupus KU autoantigen protein P70. Gel shift and supershift experiments using monoclonal antibodies toward Ku antigen and its individual subunits, and utilizing DP2 and other mutant oligonucleotides with purified nuclear protein extracts from control and cytokine-treated A549 cells, confirmed our findings. Furthermore, electroporation of neutralizing anti-Ku70, Ku 80 and Ku70/80 antibodies into A549 cells totally suppressed IL-13 and IL-4-stimulated 15-LO-1 induction in these cells. Further, immunoprecipitation experiments data suggests that IL-4 and IL-13 activate Ku antigens and 15-LO-1 expression through distinct signaling events. In summary, in A549 cells, Ku antigen is induced in response to the cytokines, IL-13 and -4, and a 29 bp region within the -353 to -304 bp region of the 15-LO-1 promoter is required for its binding and subsequent induction of 15-LO-1 gene expression. The findings may provide an important link between the established dysregulated function of Ku antigen in auto-immune diseases, such as systemic lupus erythematosus and thyroiditis, and the increasingly recognized 'anti-inflammatory' role of 15-LO-1.

Usefulness of thyrotropin (TSH)-releasing hormone test and nocturnal surge of TSH for diagnosis of isolated deficit of TSH secretion

Six patients with idiopathic isolated deficit of TSH secretion were examined and reported on. Their clinical symptoms and routine biochemical data were unclear and were not specific for hypothyroidism. Serum triiodothyronine, free thyroxine and TSH levels were slightly low or low-normal. Basal metabolic rate and thyroidal (123)I-uptake were also slightly low or low-normal. The response of serum TSH to TRH stimulation was blunted in all patients. No nocturnal surge of serum TSH level could be seen in any of the patients. Empty sella was revealed in three patients, and pituitary microadenoma in one patient via magnetic resolution imaging. Antihuman pituitary cytosol antibody was seen in five patients. Autoimmunity may have played a role in the pathogenesis of idiopathic isolated TSH deficiency. Routine examination of thyroid function cannot easily detect this disease. TSH response to TRH stimulation and nocturnal surge of TSH should be examined when this disease is suspected.

Glucocorticoid-induced insulin resistance associates with activation of protein kinase C isoforms

We studied glucocorticoid-induced insulin resistance and possible role of protein kinase C (PKC). Pretreatment with dexamethasone, prednisolone and corticosterone for 60 min decreased insulin-induced [3H] 2-deoxyglucose (DOG) uptake in isolated rat adipocytes. Preincubation with Go6976, LY379196 or myristoylated PKC pseudosubstrate, conventional PKC inhibitor, but not cycloheximide or RU38486, recovered dexamethasone-induced insulin resistance. Dexamethasone activated immunoprecipitates with anti-PKC alpha, beta, and zeta antibodies. PKC zeta activity in adipocytes increased to 163%, and 264% from basal level (100%) with dexamethasone and insulin treatment, respectively. Dexamethasone provoked redistribution of both PKC beta and zeta from the cytosol to the membrane. These results indicate that dexamethasone activates both conventional and atypical PKC. However, conventional PKC is more important in glucocorticoid-induced insulin resistance.

Mycobacterium tuberculosis phagosomes exhibit altered calmodulin-dependent signal transduction: contribution to inhibition of phagosome-lysosome fusion and intracellular survival in human macrophages

Mycobacterium tuberculosis successfully parasitizes macrophages by disrupting the maturation of its phagosome, creating an intracellular compartment with endosomal rather than lysosomal characteristics. We have recently demonstrated that live M. tuberculosis infect human macrophages in the absence of an increase in cytosolic Ca(2+) ([Ca(2+)](c)), which correlates with inhibition of phagosome-lysosome fusion and intracellular viability. In contrast, killed M. tuberculosis induces an elevation in [Ca(2+)](c) that is coupled to phagosome-lysosome fusion. We tested the hypothesis that defective activation of the Ca(2+)-dependent effector proteins calmodulin (CaM) and CaM-dependent protein kinase II (CaMKII) contributes to the intracellular pathogenesis of tuberculosis. Phagosomes containing live M. tuberculosis exhibited decreased levels of CaM and the activated form of CaMKII compared with phagosomes encompassing killed tubercle bacilli. Furthermore, ionophore-induced elevations in [Ca(2+)](c) resulted in recruitment of CaM and activation of CaMKII on phagosomes containing live M. tuberculosis. Specific inhibitors of CaM or CaMKII blocked Ca(2+) ionophore-induced phagosomal maturation and enhanced the bacilli's intracellular viability. These results demonstrate a novel role for CaM and CaMKII in the regulation of phagosome-lysosome fusion and suggest that defective activation of these Ca(2+)-activated signaling components contributes to the successful parasitism of human macrophages by M. tuberculosis.

Interleukin-4 acts at the locus of the antigen-presenting dendritic cell to counter-regulate cytotoxic CD8+ T-cell responses

The mechanism underlying suppression of immune responses by interleukin-4 (IL-4) has remained unexplained. Here we show that the antigen-presenting dendritic cell is central to counter-regulation of autoimmune disease by IL-4. IL-4 acts at the locus of the dendritic cell to decrease the cytolytic T-cell response, preventing autoimmunity. Stimulation of cytotoxic precursors by antigen pulsed dendritic cells induces their differentiation but the process is blocked by IL-4. IL-4-influenced DC produce distinct effects on CD8+ T cells depending on their state of activation. The molecular basis for this regulation is the alteration of the expression ratio of the costimulatory ligands B7.1/B7.2 on dendritic cells. Our findings demonstrate that B7.2 induces expansion of CD8+ T cells and B7.1 governs their acquisition of cytolytic activity. IL-4 influences the dendritic cell to elicit qualitative differences in T-cell responses, providing the basis for counter-regulation mediated by IL-4.

Characteristics of the free cytosolic calcium timelag following IgE-mediated stimulation of human basophils: significance for the nonreleasing basophil phenotype

These studies examine characteristics of the quiescent period (timelag) of the free cytosolic calcium ([Ca++]i) elevation that follows stimulation of human basophils through the IgE receptor. Previous studies established that the [Ca++]i timelag was sensitive to the rate of ligand binding, but little else is known about this response characteristic. The [Ca++]i timelag could be lengthened using antigenic stimulation that is rapid but only weakly induces secretion: tenfold differences in the "strength" of the stimulus, as assessed by histamine release, are associated with threefold differences in the timelag. Inhibiting p53/56lyn kinase with low concentrations of the specific inhibitor, PP1, lengthened the [Ca++]i timelag dramatically. PP1 was also found to delay the onset of syk phosphorylation and histamine release. Staurosporine and genistein, which are known to inhibit early tyrosine kinases, had, at best, only modest effects on the [Ca++]i timelag. Specific inhibitors of protein kinase C (PKC) had no effect on the [Ca++]i timelag, and direct activation of PKC with PMA had only very modest effects on the timelag. Contrary to expectations, basophils with the so-called nonreleasing phenotype demonstrated an IgE-mediated [Ca++]i response at the single-cell level. However, the length of [Ca++]i timelag in nonreleasing basophils was threefold longer than normally found in releasing basophils. Furthermore, the [Ca++]i response was significantly more asynchronous than in releasing basophils and lacking in a sustained [Ca++]i elevation. These studies indicate that the [Ca++]i timelag following stimulation through the IgE receptor is sensitive to inhibition of lyn kinase but not other agents that have been demonstrated to inhibit early tyrosine kinases previously. However, only one characteristic of the [Ca++]i response phenotype of nonreleasing basophils--the [Ca++]i timelag but not the absence of a sustained [Ca++]i elevation--could be mimicked by inhibition of lyn kinase with PP1.

Cell injury releases endogenous adjuvants that stimulate cytotoxic T cell responses

General immunostimulants (adjuvants) are essential for generating immunity to many antigens. In bacterial infections, adjuvants are provided by components of the microorganism, e.g., lipopolysaccharide. However, it is unclear what provides the adjuvant effect for immune responses that are generated to tumors and many viruses. Here we show that cell injury and death of tumor or even normal cells provide a potent adjuvant effect for the stimulation of cytotoxic T lymphocyte responses. This adjuvant activity is constitutively present in the cytoplasm of cells and is increased in the cytoplasm of cells dying by apoptosis. The release of these components stimulates immune responses both locally and at a distance, and provides a simple mechanism to alert the immune system to potential danger in almost all pathological situations.