Diagnostic value of interleukin-12 p40 in tuberculous pleural effusions.

The diagnosis of tuberculous pleural effusion (TBPE) is frequently problematic. Several markers of TBPE in pleural fluid have been evaluated, with different results. Pleural effusions from 96 patients were classified on the basis of definitive diagnosis as tuberculous (n = 39), neoplastic (n = 42) or parapneumonic (n = 15). Adenosine deaminase (ADA), ADA isoform ADA-2, interferon (IFN)-gamma, CD3(+)/DR(+) T-lymphocytes and interleukin (IL)-12 p40 were determined in all 96 effusions. The efficiency of IL-12 p40 for diagnosis of TBPEs was evaluated, in comparison with those of the other parameters, by comparing the areas under their receiver operating characteristics. With the threshold value of 550 pg.mL(-1), IL-12 p40 had a sensitivity of 92.3% (36 out of 39) and specificity of 70.2% (17 false positives). The misclassification rate of IL-12 p40 was significantly greater than those of ADA-2 and ADA. Among TBPEs, ADA correlated significantly with ADA-2, and IFN-gamma with ADA and IL-12 p40. Although tuberculous pleural effusions show values of interleukin-12 p40 that are significantly higher than neoplastic and parapneumonic fluids, this parameter is less efficient than adenosine deaminase, adenosine deaminase isoform 2 and interferon-gamma. Its routine determination is, accordingly, not justified.

Identification of a tumor-specific allo-HLA-restricted γδTCR.

γδT cells are key players in cancer immune surveillance because of their ability to recognize malignant transformed cells, which makes them promising therapeutic tools in the treatment of cancer. However, the biological mechanisms of how γδT-cell receptors (TCRs) interact with their ligands are poorly understood. Within this context, we describe the novel allo-HLA-restricted and CD8α-dependent Vγ5Vδ1TCR. In contrast to the previous assumption of the general allo-HLA reactivity of a minor fraction of γδTCRs, we show that classic anti-HLA-directed, γδTCR-mediated reactivity can selectively act on hematological and solid tumor cells, while not harming healthy tissues in vitro and in vivo. We identified the molecular interface with proximity to the peptide-binding groove of HLA-A*24:02 as the essential determinant for recognition and describe the critical role of CD8 as a coreceptor. We conclude that alloreactive γδT-cell repertoires provide therapeutic opportunities, either within the context of haplotransplantation or as individual γδTCRs for genetic engineering of tumor-reactive T cells.

Behaviour of nucleated cells in various types of pleural effusion. / Comportamiento de las células nucleadas en los distintos tipos de derrame pleural.

INTRODUCTION: To know the behavior of cellular components of pleural fluid can help focus the differential diagnosis of a pleural effusion. Our objective was to assess their composition in different types of pleural effusions and assess whether it provides relevant clinical information. PATIENTS AND METHODS: Observational, cross-sectional and retrospective study in which the cellular components of pleural effusions of different etiology were analyzed. Pleural effusions were classified as neutrophilic, lymphocytic (≥50% of each one of them), eosinophilic (≥10%) or mesothelial (>5%) and were grouped into six diagnostic categories RESULTS: 1.467 patients were studied (354 heart failure; 59 other transudates; 349 paraneumonic; 133 tuberculous; 397 malignant and 175 other exudates). The predominance cell was lymphocytic in heart failure (44,4%), uncomplicated parapneumonic (29,2%), tuberculosis (88%) and malignant (49,6%); neutrophilic in parapneumonic (57%) and malignant (9,6%); eosinophilic in malignant (6,3%) and mesotelial in tuberculosis (12%). The most frequent etiologies with lymphocyte count ≥80% were tuberculosis (35,1%) and malignant (23,3%). Parameters with higher discriminating accuracy were: leukocytes (transudates: AUC 0,835) and percentage of neutrophils (empyemas: AUC 0,906 and complicated parapneumonic+empyemas: AUC 0,907). CONCLUSIONS: Nucleated cell counts will help focus the etiology of pleural effusions, since each etiology often have a characteristic cell predominance. The percentage of nucleated cells in pleural fluid not ruled out tuberculosis if there is a high count of mesothelial cells, nor a parapneumonic effusion with lymphocytic predominance, or malignancy with ≥80% lymphocytes.

Tuberculous pleurisy: a study of 254 patients.

OBJECTIVES: To determine the age at which tuberculous pleural effusions occur, the radiological and biochemical characteristics of the effusions, the sensitivities of the various diagnostic tests, and the utility of combining clinical, radiological, and analytic data in diagnosis. METHODS: We studied the case histories of 254 patients in whom tuberculous pleural effusions were diagnosed with certainty between January 1, 1989, and June 30, 1997, in a Spanish university hospital in a region with a high incidence of tuberculosis. RESULTS: The mean (+/-SD) age of the patients was 34.1+/-18.1 years, and 62.2% were younger than 35 years. The effusion was on the right side in 55.9% of patients, on the left side in 42.5% of patients, and on both sides in 1.6% of patients. In 81.5% of patients, less than two thirds of the hemithorax was affected. Associated pulmonary lesions were detected in 18.9% of patients, of whom 14.6% exhibited cavitation. In 93.3% of the effusions, more than 50% of leukocytes were lymphocytes, and almost all had the biologic characteristics of exudates (98.8% had high total protein contents, 94.9% had high cholesterol levels, and 82.3% had high lactate dehydrogenase levels). All but 1 effusion (99.6%) had an adenosine deaminase (ADA) concentration higher than 47 U/L, 96.8% (123/127) of the effusions had high ADA2 levels, and 89% (73/82) of the effusions had high interferon gamma levels. Adenosine deaminase 2 contributed 72.2%+/-12.5% (mean +/- SD) of total ADA activity. Total ADA activity was significantly correlated with ADA2 (r = 0.83) and with interferon gamma (r = 0.30) levels. Definitive diagnosis was based on the observation of caseous granulomas in pleural biopsy tissue samples in 79.8% of patients, on the results of biopsy cultures in 11.7% of patients, and on pleural effusion cultures in the remaining 8.5% of patients. Results of the tuberculin skin test were positive in only 66.5% of patients. CONCLUSIONS: In these patients, lymphocyte-rich exudative pleural effusions occurred, on average, at a young age, with no preference for either the right or the left side; normally affected no more than two thirds of the hemithorax; and were generally unaccompanied by pulmonary infiltrates. High ADA concentration was a highly sensitive diagnostic sign and was caused by a rise in ADA2 concentration. The most sensitive criterion based on pleural biopsy was the observation of caseous granulomas, and culture of biopsy material further increased overall sensitivity. Negative skin test results were no guarantee of the effusion being nontuberculous. This, together with the low mean age of the patients and the low frequency of associated pulmonary lesions, suggests that tuberculous pleural effusion is a primary form of tuberculosis in this region.

Retroviral vector-mediated expression in primary human T cells of an endoplasmic reticulum-retained CD4 chimera inhibits human immunodeficiency virus type-1 replication.

Intracellular expression of genes that inhibit key steps in the human immunodeficiency virus (HIV-1) replicative cycle could offer an alternative therapy for AIDS treatment. One of these approaches involves the inhibition of env protein maturation through the expression of CD4 molecules with added exogenous sequences that promote their retention in the endoplasmic reticulum (ER). We have tested this strategy using a CD4 chimera (CD4epsilon10) containing an ER retention sequence derived from the TCR CD3-epsilon chain. Transfection of CD4epsilon10 in the human T cell line Jurkat made it resistant to infection with two different HIV-1 isolates, which was evaluated by measuring p24 antigen production, induction of apoptosis, and syncytia formation. Furthermore, polymerase chain reaction (PCR) analysis of genomic DNA showed no traces of the proviral HIV-1 genome in CD4epsilon10-transfected cells, suggesting it was not maintained latently in these cells. To facilitate the delivery of the CD4epsilon10 chimera to primary cells from AIDS patients, a Moloney-based retroviral vector was constructed that expresses CD4epsilon10 under the transcriptional control of the HIV-1 long terminal repeat (LTR) promoter. Transduction of the MT-2 human T cell line with this vector rendered it resistant to infection with HIV-1 by a process that involved the inhibition of gp160 proteolytic processing. Finally, transduction of the CD4epsilon10 chimera into T lymphoblasts derived from asymptomatic HIV-infected individuals demonstrated a protective effect, resulting in both an increased cellular proliferation rate and an increased percentage of CD4+ cells. These results suggest that it is feasible to use retroviral transduction of CD4epsilon10 as a gene therapy approach for AIDS treatment.

The etiology of pleural effusions in an area with high incidence of tuberculosis.

To investigate the etiology of pleural effusions in our region, we undertook a prospective study of patients with this condition in our centers. During a 5-year period, we studied 642 pleural effusion patients aged 57.1 +/- 21.1 years, of whom 401 were men aged 56.5 +/- 21 years and 241 were women aged 57.8 +/- 21.4 years; the male/female ratio was 1.6:1. The most frequent cause of pleural effusion was tuberculosis (25%), followed by neoplasia (22.9%) and congestive heart failure (17.9%). The etiology of 48 cases (7.5%) remained uncertain. In the neoplastic effusion group, the most frequent locations of the primary tumor were lung (32.6%), breast (11.5%), lymphoma (10.8%), and ovary (7.5%); in 21 cases (14.3% of the neoplastic group), it was not possible to identify the primary tumor. The 111 patients aged younger than 40 years with tuberculous effusions made up 69.4% of tuberculous effusion cases and the same percentage of patients younger than 40 years; the proportion of effusions that were tuberculous peaked in the 11- to 30-year-old age group and declined steadily thereafter. Of the patients with neoplastic effusions, 83% were older than 50 years; the proportion of effusions that were neoplastic rose steadily from zero in the 0- to 30-year-old age group to a peak among 60- to 70-year-olds. The age-wise distribution of effusions secondary to congestive heart failure was similar to that of neoplastic effusions. Of the effusions secondary to congestive heart failure, 86% (99/115) affected the right pleura or both, and 83% of effusions secondary to pulmonary thromboembolism (15/18) affected the right side. Neoplastic, tuberculous, parapneumonic, empyematous, and other exudative effusions showed no preference for either side. Of the 97 bilateral effusions, 77 (79.4%) were secondary to heart failure (59, 60.8%) or neoplasia (18, 18.6%). We conclude that in our region, the most frequent cause of pleural effusion is tuberculosis, followed by neoplasia and congestive heart failure. We suggest that all those interested in pleural disease should determine the etiologic pattern of pleural effusion in their region with a view to the adoption of regionally optimized diagnostic and therapeutic attitudes.

Diagnosis of tuberculous pleurisy using the biologic parameters adenosine deaminase, lysozyme, and interferon gamma.

We compared the parameters pleural adenosine deaminase (PADA, determined in 405 patients), the PADA/serum ADA ratio (P/SADA; 276 cases), pleural lysozyme (PLYS, 276 cases), the PLYS/serum LYS ratio (P/SLYS; 276 cases), and pleural interferon gamma (IFN, 145 cases) regarding their ability to differentiate tuberculous pleural effusions from others. The 405 pleural effusions were classified by previously established criteria as tuberculous (91), neoplastic (110), parapneumonic (58), empyemas (10), transudates (88), or miscellaneous (48). The intermean differences between the tuberculous group and each of the others were statistically significant for all five parameters (p < 0.01 for PLYS and P/SLYS with respect to the empyema group; p < 0.001 otherwise), except for PADA and P/SADA with respect to the empyema group. All the tuberculous pleurisy cases had PADA values of 47 U/L or more, as compared to only 5 percent of the other cases (sensitivity, 100 percent; specificity, 95 percent). P/SADA was above 1.5 in 85.7 percent of tuberculous effusions and 11 percent of the others (sensitivity, 85.7 percent; specificity, 89 percent). PLYS, with a diagnostic threshold of 15 g/ml, had a sensitivity of 85.7 percent and a specificity of 61.6 percent; P/SLYS, with a threshold of 1.1, had a sensitivity of 67.3 percent and a specificity of 90.3 percent; and IFN, with a threshold of 140 pg/ml, had a sensitivity of 94.2 percent and a specificity of 91.8 percent. The lowest misclassification rate was achieved by PADA, with statistically significant differences (p < 0.001) with respect to P/SADA, PLYS, and P/SLYS, but not with respect to IFN. The only significant pairwise correlations among these parameters were between P/SLYS and PADA and between P/SLYS and P/SADA. We conclude that PADA and IFN are useful parameters for early diagnosis of tuberculous pleurisy, and that the other parameters considered have no advantages over PADA and IFN for this purpose (though the high specificity of P/SLYS may be noted).

Cholesterol: a useful parameter for distinguishing between pleural exudates and transudates.

Previously established criteria were used to classify 253 pleural effusions as transudates (65 cases), neoplastic exudates (67 cases), tuberculous exudates (65 cases), or miscellaneous exudate (56 cases). The parameters pleural LDH (PLDH), pleural LDH/serum LDH ratio (P/SLDH), and pleural protein/serum protein ratio (P/SPROT) were compared with pleural cholesterol (PCHOL) and the pleural cholesterol/serum cholesterol ratio (P/SCHOL) with regard to their usefulness for distinguishing between pleural exudates and transudates. The PCHOL values determined were 28.5 +/- 12.8 mg/dl for transudates, 88.1 +/- 30 mg/dl for neoplastic exudates, 96.5 +/- 28 mg/dl for tuberculous exudates, and 88 +/- 35.9 mg/dl for the miscellaneous group; the differences between the transudate group and the others are statistically significant (p less than 0.001). The sensitivity and specificity of P/SPROT for diagnosis of exudates were both 89 percent; the sensitivity of PLDH was 67 percent and its specificity was 95 percent; the sensitivity and specificity of P/SLDH were both 84.6 percent. Using Light's three criteria as a battery, the sensitivity was 94.6 percent and its specificity was 78.4 percent. All the transudates and 17 (9 percent) of the 188 exudates had PCHOL values below 55 mg/dl, so that with this threshold, PCHOL had a sensitivity of 91 percent and a specificity of 100 percent for diagnosis of exudates. With a threshold of 0.3, P/SCHOL had a sensitivity of 92.5 percent and a specificity of 87.6 percent. The number of misclassifications by PCHOL was less than with any other of the parameters, with statistically significant differences with respect to PLDH (p less than 0.001) and P/SLDH (p less than 0.01). We conclude that determination of PCHOL and P/SCHOL is of great value for distinguishing between pleural exudates and transudates, and should be included in routine laboratory analysis of pleural effusions.

Xpert® MTB/RIF in pleural fluid for the diagnosis of tuberculosis.

An automated nucleic acid amplification assay that simultaneously identifies Mycobacterium tuberculosis and rifampicin resistance, the Xpert® MTB/RIF test, has undergone extensive evaluation in sputum samples. Our aim was to define its diagnostic accuracy when performed on pleural fluid specimens. In 67 patients with pleural effusions, of whom half had tuberculous pleuritis, Xpert yielded 15% sensitivity and 100% specificity in the detection of tuberculosis (TB). Positive Xpert results tended to be more common in patients with microbiologically confirmed TB. Due to its low sensitivity, Xpert testing of pleural fluids has a limited role in the work-up of pleural effusions.

Comportamiento de las células nucleadas en los distintos tipos de derrame pleural / Behaviour of nucleated cells in various types of pleural effusion

Introducción. El conocimiento del comportamiento de los componentes celulares del líquido pleural puede ayudar a enfocar el diagnóstico diferencial de un derrame pleural. El objetivo es evaluar su composición en los distintos tipos de derrames y valorar si proporciona información clínica relevante. Pacientes y métodos. Estudio observacional, transversal y retrospectivo en el que se analiza el componente celular de derrames pleurales de diversa etiología. Los derrames se clasificaron como neutrofílicos, linfocíticos (≥50% de cada uno de ellos), eosinofílicos (≥10%) o mesoteliales (>5%) y se agruparon en 6 categorías diagnósticas. Resultados. Se estudiaron 1.467 pacientes (354 insuficiencia cardiaca; 59 otros trasudados; 349 paraneumónicos; 133 tuberculosos; 397 neoplásicos y 175 otros exudados). El predominio celular fue linfocítico en la insuficiencia cardiaca (44,4%), paraneumónicos no complicados (29,2%), tuberculosis (88%) y neoplasias (49,6%); neutrofílico en los paraneumónicos (57%) y neoplásicos (9,6%); eosinofílico en las neoplasias (6,3%) y mesotelial en las tuberculosis (12%). Las etiologías más frecuentes con un recuento linfocitario ≥80% fueron tuberculosis (35,1%) y neoplasias (23,3%). Los parámetros con mayor capacidad discriminante fueron: leucocitos (trasudados: AUC 0,835) y porcentaje de neutrófilos (empiemas: AUC 0,906 y paraneumónicos complicados + empiemas: AUC 0,907). Conclusiones. Los recuentos de células nucleadas ayudan a enfocar la etiología del derrame pleural, ya que cada etiología suele tener un predominio celular característico. El porcentaje de células nucleadas en el líquido pleural no puede descartar tuberculosis si existe un recuento elevado de células mesoteliales, ni un derrame paraneumónico ante un predominio linfocítico, o malignidad con un recuento de linfocitos ≥80% (AU)

Introduction. To know the behavior of cellular components of pleural fluid can help focus the differential diagnosis of a pleural effusion. Our objective was to assess their composition in different types of pleural effusions and assess whether it provides relevant clinical information. Patients and methods. Observational, cross-sectional and retrospective study in which the cellular components of pleural effusions of different etiology were analyzed. Pleural effusions were classified as neutrophilic, lymphocytic (≥50% of each one of them), eosinophilic (≥10%) or mesothelial (>5%) and were grouped into six diagnostic categories. Results. 1.467 patients were studied (354 heart failure; 59 other transudates; 349 paraneumonic; 133 tuberculous; 397 malignant and 175 other exudates). The predominance cell was lymphocytic in heart failure (44,4%), uncomplicated parapneumonic (29,2%), tuberculosis (88%) and malignant (49,6%); neutrophilic in parapneumonic (57%) and malignant (9,6%); eosinophilic in malignant (6,3%) and mesotelial in tuberculosis (12%). The most frequent etiologies with lymphocyte count ≥80% were tuberculosis (35,1%) and malignant (23,3%). Parameters with higher discriminating accuracy were: leukocytes (transudates: AUC 0,835) and percentage of neutrophils (empyemas: AUC 0,906 and complicated parapneumonic+empyemas: AUC 0,907). Conclusions. Nucleated cell counts will help focus the etiology of pleural effusions, since each etiology often have a characteristic cell predominance. The percentage of nucleated cells in pleural fluid not ruled out tuberculosis if there is a high count of mesothelial cells, nor a parapneumonic effusion with lymphocytic predominance, or malignancy with ≥80% lymphocytes (AU)

Receptor engagement transiently diverts the T cell receptor heterodimer from a constitutive degradation pathway.

In the absence of ligand, the T cell receptor (TCR)/CD3 complex is continuously internalized and recycled to the cell surface, whereas receptor engagement results in its down-regulation. The present study shows that the TCR and CD3 components follow different fates accompanying their constitutive internalization. Although the CD3 moiety is recycled to the cell surface, the TCR heterodimer is degraded and replaced by newly synthesized chains. Since the TCR heterodimer cannot reach the cell membrane on its own, we propose a model in which recycling CD3 is transported along a retrograde pathway to the endoplasmic reticulum, where it associates with newly made TCR. Interestingly, engagement of the TCR.CD3 complex by superantigen resulted not only in the down-regulation of the TCR and CD3 components but also caused a transient stabilization of the TCR heterodimer. This suggests that TCR engagement diverts the TCR heterodimer from a degradation to a recycling pathway. Contrary to CD3, the intracellular fate of the TCR heterodimer is thus regulated, providing a mechanism for rapidly replacing nonfunctional TCR during intrathymic development of T cells.

Megalomicin inhibits HIV-1 replication and interferes with gp160 processing.

The inhibitory effects on HIV replication of megalomicin (MGM, an inhibitor of intra-Golgi vesicle transport, have been studied. In experiments at low multiplicity of infection on Jurkat and MT2 cell lines. MGM inhibited the production of p24 antigen, the formation of syncytia, and the induction of apoptosis at concentrations below 5 microM. Furthermore, PCR analysis of genomic DNA showed that, in the presence of MGM, HIV-1 had been eradicated from the culture. MGM also inhibited replication of primary isolates of HIV-1 in blood lymphoblasts and more importantly, at 1 microM, MGM inhibited depletion of CD4+ T cells in cultures of blood lymphocytes from seropositive patients. Finally, MGM inhibited the generation of infectious virions and the processing of the envelope protein precursor gp160 to its mature forms, resulting in the rapid degradation of gp 160. These data suggest that MGM induces a powerful inhibitory effect on HIV-1 replication at nontoxic concentrations by preventing the processing of HIV-1 gp160 envelope protein and the subsequent formation of infectious viral particles.

A novel adenylylation process in liver plasma membrane-bound proteins.

Rat liver plasma membrane contains five distinct polypeptides of apparent molecular mass of 130, 120, 110, 100, and 86 kDa which are labeled upon incubation with [alpha-32P]ATP as well as with [gamma-32P]ATP. Covalently bound adenosine 5'-monophosphate to some of the polypeptides was identified using nonhydrolyzable analogues of ATP. Chase experiments of alpha-32P-nucleotide-labeled polypeptides with different nonradiolabeled phosphocompounds and sensitivity to different inhibitors demonstrate that the 86-kDa polypeptide is a phosphoesterase, forming a catalytic intermediate. On the other hand, the comparative slow rate of turnover of the polypeptides of higher molecular mass (130, 120, 110, and 100 kDa) suggests that the bound AMP could play a regulatory rather than a catalytic role. Using the nonhydrolyzable ATP analogue [alpha, beta-methylene]ATP and dilution experiments with Triton X-100-solubilized membranes, it has been possible to identify the 130-kDa adenylylated polypeptide as a possible target of an adenylylating system. These polypeptides, except the 86-kDa phosphoesterase, are affected in their electrophoretic mobility in the absence of beta-mercaptoethanol. An intercatenary disulfide bond(s) appear(s) to link the polypeptide(s) of 120 kDa and/or 110 kDa in a dimeric structure of apparent molecular mass of 240 kDa. All five polypeptides labeled with [alpha-32P]ATP are glycoproteins bound to the cell plasma membrane.

Calmodulin inhibits the epidermal growth factor receptor tyrosine kinase.

We demonstrate in this report that the epidermal growth factor (EGF) receptor from rat liver can be isolated by calmodulin affinity chromatography by binding in the presence of Ca2+ and elution with a Ca(2+)-chelating agent. The bulk of the EGF receptor is not eluted by a NaCl gradient in the presence of Ca2+. We ascertained the identity of the isolated receptor by immunoblot and immunoprecipitation using a polyclonal antibody against an EGF receptor from human origin. The purified receptor is autophosphorylated in tyrosine residues in an EGF-stimulated manner, and EGF-dependent phosphorylation of serine residues was also detected. Both the EGF and the transforming growth factor-alpha stimulate the tyrosine-directed protein kinase activity of the isolated receptor with similar affinities. Furthermore, we demonstrate that calmodulin inhibits the EGF-dependent tyrosine-directed protein kinase activity associated to the receptor in a concentration-dependent manner. This inhibition is partially Ca2+ dependent and is not displaced by increasing the concentration of EGF up to an EGF/calmodulin ratio of 10 (mol/mol). In addition, calmodulin was phosphorylated in an EGF-stimulated manner in the presence of a basic protein (histone) as cofactor and in the absence, but not in the presence, of Ca2+.

Inhibition of the adenylylation of liver plasma membrane-bound proteins by plant and mammalian lectins.

Liver plasma membrane contains four major (130-kDa, 120-kDa, 110-kDa and 100-kDa) sialic acid-containing glycopolypeptides that are able to undergo adenylylation, as well as phosphorylation (San José et al. (1990) J. Biol. Chem. 265; 20653-20661). To gain insight into the regulation of these processes, lectins are employed to probe the extent of influence of their interaction with membrane fractions for these reactions. We demonstrate that the beta-galactoside-specific lectins from bovine heart and mistletoe at low concentrations inhibit the adenylylation of this set of plasma membrane glycopolypeptides. The extent of phosphorylation of these polypeptides is also reduced although to a lesser degree. Concanavalin A, too, inhibits the adenylylation of the plasma membrane glycopolypeptides, although higher concentrations of this lectin were required, whereas wheat germ lectin has only a very small inhibitory effect. The adenylylable polypeptides were isolated by concanavalin A-agarose chromatography upon elution with mannose. In agreement with this result, control experiments with a panel of neoglycoproteins indicate that mannose residues appear to be required for the concanavalin A-induced inhibition of the adenylylation. Neoglycoproteins containing mannose 6-phosphate, lactose, fucose, or sialic acid instead of mannose lack the ability to protect the adenylylation from the inhibitory action of concanavalin A. In contrast, none of the above-mentioned neoglycoproteins, nor asialofetuin, nor galactose-containing saccharides protect the adenylylation against the inhibitory effect of both the mistletoe and bovine heart lectins, emphasizing the importance of either high affinity carbohydrate ligands in the overall process, or other ligand sites for the lectins beside carbohydrates to affect the regulation of the adenylylation system.

Differential cytosolic tail dependence and intracellular fate of T-cell receptors internalized upon activation with superantigen or phorbol ester.

Activation of T lymphocytes by T-cell receptor (TCR) ligands such as peptide/MHC complexes, superantigens or anti-TCR mAbs, or by pharmacological activators of protein kinase C such as phorbol esters, results in the internalization and cell surface downregulation of TCRs. We investigated the role of internalization motifs located in the cytosolic region of CD3 gamma in the internalization of TCR complexes induced by enterotoxin superantigens, anti-TCR mAbs or phorbol esters. To this end, a series of CD3 gamma mutants were expressed in a CD3 gamma-deficient variant of the human T-cell line Jurkat. We found that serine126 and the di-leucine motif (Leu131-Leu132) are required for phorbol-ester-induced TCR downregulation, but they are not necessary for enterotoxin superantigen or antibody-induced TCR downregulation. Moreover, the tyrosine-based motifs (residues 138 to 141 and 149 to 152) are not required either for phorbol aster or for superantigen or antibody-induced TCR downregulation. Confocal microscopy analysis reveals that TCR complexes accumulate in an early endocytic/recycling compartment upon activation of cells with phorbol esters, whereas TCRs internalized upon activation with superantigen or anti-TCR mAbs are routed to lysosomes. Consistent with this intracellular localization, TCRs internalized in response to phorbol ester are not degraded and can be reexpressed on the cell surface. In contrast, TCRs internalized upon superantigen activation are degraded.

Adenosine deaminase (ADA) isoenzyme analysis in pleural effusions: diagnostic role, and relevance to the origin of increased ADA in tuberculous pleurisy.

The rise in adenosine deaminase (ADA) activity in the pleural fluid of tuberculous pleurisy patients, though used for diagnosis, is of unknown origin. In this work, we determined ADA activity and the activities of 2'-deoxyadenosine deaminase and ADA-2 in 350 patients. We also considered whether the results throw light on the origin of high pleural fluid ADA in tuberculous pleurisy and estimated the diagnostic efficiency of 2'-deoxyadenosine deaminase, ADA-2 and total ADA activities with and without the inclusion of the 2'-deoxyadenosine deaminase/ADA activity ratio in a combined criterion. The 350 pleural effusions were classified by previously established criteria as transudates (60 males/18 females) or as tuberculous (49 males/27 females), neoplastic (50 males/39 females), parapneumonic (36 males/19 females), empyematous (11 males/3 females), or miscellaneous (25 males/13 females) exudates. Total ADA, ADA-2 and 2'-deoxyadenosine deaminase activities were, respectively, 127.5 +/- 2.9, 103 +/- 29.5 and 42.8 +/- 14 U.L-1 in tuberculous exudates. With diagnostic thresholds of 47, 40 and 22 U.L-1 respectively, the sensitivities of ADA, ADA-2 and 2'-deoxyadenosine deaminase for tuberculosis were 100, 100 and 95%; their specificities 91, 96 and 92%; and their efficiencies 93, 97 and 93%, respectively. One hundred and one effusions (all 76 tuberculous, 12 neoplastic, 4 parapneumonic and 9 empyematous exudates) had total ADA levels > 47 U.L-1; of these, 8 neoplastic, 1 parapneumonic and all the tuberculous exudates had a 2'-deoxyadenosine deaminase/ADA activity ratio < 0.49. The criterion of simultaneously having ADA > 47 U.L-1, ADA-2 > 40 U.L-1 and a 2'-deoxyadenosine deaminase/ADA activity ratio < 0.49 was satisfied by all the tuberculous effusions but only eight others (all neoplastic) (sensitivity 100%, specificity 97%, efficiency 98%). We conclude that: 1) high total ADA activity in tuberculous pleural effusions is due mainly to an increase in ADA-2, and, therefore, originated from the only known source monocytes and macrophages; 2) ADA-2 was a more efficient diagnostic marker of tuberculous pleurisy than total ADA activity, although the difference was not statistically significant; and 3) among effusions with high total ADA the 2'-deoxyadenosine deaminase/ADA activity ratio differentiates tuberculous effusions from empyemas and parapneumonic effusions, but fails to discriminate well between tuberculous and neoplastic effusions.

Triggering the TCR complex causes the downregulation of nonengaged receptors by a signal transduction-dependent mechanism.

Downregulation of the TCR complex is believed to be intimately tied to T cell activation, allowing serial triggering of receptors and desensitization of stimulated cells. We studied transfected and transgenic T cells expressing CD3zeta chimeras to demonstrate that ligand engagement of the TCR or chimeras causes comodulation of nonengaged receptors. Comodulation required protein tyrosine kinase activity but not trans-phosphorylation of nonengaged receptors. The TCR appears to be downregulated by at least two mechanisms. One mechanism requires direct engagement, independent of signaling. The second requires signaling and downregulates nontriggered receptors. These results shed new light on the process of TCR downregulation and indicate that the number of downregulated TCRs cannot be assumed to equal the number of engaged receptors.

Assembly of the TCR/CD3 complex: CD3 epsilon/delta and CD3 epsilon/gamma dimers associate indistinctly with both TCR alpha and TCR beta chains. Evidence for a double TCR heterodimer model.

The TCR/CD3 complex is composed of six subunits which are expressed on the cell surface in a coordinate fashion after assembly in the endoplasmic reticulum (ER). The TCR/CD3 complex is assembled after a series of pairwise interactions involving the formation of dimers of CD3 epsilon with either CD3 gamma or CD3 delta. These dimers assemble with TCR alpha and TCR beta chains, and finally, the CD3 zeta homodimer is added to allow export of the full complex from the ER. A model has been proposed suggesting that during assembly the CD3 epsilon/CD3 gamma dimer interacts exclusively with TCR beta and the CD3 epsilon/CD3 delta dimer with TCR alpha to form a complex with a single TCR alpha/beta heterodimer. We show in this study, by immunoprecipitation and two-dimensional gel electrophoresis, that in the human T cell line Jurkat as well as in total human thymocytes, this preferential interaction does not occur and instead, the CD3 epsilon/CD3 gamma and CD3 epsilon/CD3 delta dimers associate with both TCR chains simultaneously and indistinctly. These data are confirmed by the analysis of the TCR alpha-negative T cell line MOLT-4 in which TCR beta is found separately associated with CD3 epsilon/CD3 gamma and with CD3 epsilon/CD3 delta dimers. Indirectly, our results support a model of stoichiometry in which two TCR alpha/beta heterodimers are present in a TCR/CD3 complex. Furthermore, immunoprecipitation with anti-CD3 gamma and anti-CD3 delta antibodies from 1% NP40 and 1% Brij96 cell lysates showed that these subunits form independent partial complexes which are cross-linked through the CD3 zeta homodimer. This suggests that CD3 zeta mediates the interaction between both TCR alpha/beta heterodimers contained in the double TCR complex. Further proof for this hypothesis is obtained after analysis of a Jurkat cell transfectant containing a point mutation in the transmembrane domain of TCR beta that impairs the association of CD3 zeta. In this mutant cell line, unlike a control line with wild-type TCR beta, the CD3 gamma- and CD3 delta-containing complexes were found completely independent. Altogether, these results support a model of TCR/CD3 assembly and stoichiometry in which two TCR-alpha/beta heterodimers form two hemicomplexes containing either CD3 epsilon/gamma or CD3 epsilon/delta dimers which become associated via the CD3 zeta homodimer.