Impaired alveolarization and intra-uterine growth restriction in rats: a postnatal genome-wide analysis.

Intra-uterine growth restriction (IUGR) dramatically increases the risk of bronchopulmonary dysplasia in preterm babies, a disease characterized by arrested alveolarization and abnormal microvascular angiogenesis. We have previously described a rodent low protein diet (LPD) model of IUGR inducing impaired alveolarization, but failed to demonstrate any modification of the classical factors involved in lung development. We performed a genome-wide microarray analysis in 120 rat pups with LPD-induced IUGR and their controls, at three key time points of the alveolarization process: postnatal day 4 (P4): start of alveolarization; P10: peak of the alveolarization process and P21: end of the alveolarization process. Results were analysed using Arraymining, DAVID and KEGG software and validated by qRT-PCR and western blots. Considering a cut-off of 2:1 as significant, 67 transcripts at P4, 102 transcripts at P10 and 451 transcripts at P21 were up-regulated, and 89 transcripts at P4, 25 transcripts at P10 and 585 transcripts at P21 were down-regulated. Automatic functional classification identified three main modified pathways, 'cell adhesion molecules', 'cardiac muscle contraction' and 'peroxisome proliferator-activated receptor' (PPAR). Protein analysis confirmed involvement of the PPAR pathway, with an increase of FABP4, an activator of this pathway, at P4 and an increase of adiponectin at P21. Other data also suggest involvement of the PPAR pathway in impaired alveolarization. Our results show that deregulation of the PPAR pathway may be an important component of the mechanism inducing impaired alveolarization observed in IUGR. The complete dataset is available as GEO profiles on the Gene Expression Omnibus (GEO) database ( www.ncbi.nih.gov/geo/, GEO Accession No. GSE56956).

Cell cloning-based transcriptome analysis in Rett patients: relevance to the pathogenesis of Rett syndrome of new human MeCP2 target genes.

More than 90% of Rett syndrome (RTT) patients have heterozygous mutations in the X-linked methyl-CpG binding protein 2 (MECP2) gene that encodes the methyl-CpG-binding protein 2, a transcriptional modulator. Because MECP2 is subjected to X chromosome inactivation (XCI), girls with RTT either express the wild-type or mutant allele in each individual cell. To test the consequences of MECP2 mutations resulting from a genome-wide transcriptional dysregulation and to identify its target genes in a system that circumvents the functional mosaicism resulting from XCI, we carried out gene expression profiling of clonal populations derived from fibroblast primary cultures expressing exclusively either the wild-type or the mutant MECP2 allele. Clonal cultures were obtained from skin biopsy of three RTT patients carrying either a non-sense or a frameshift MECP2 mutation. For each patient, gene expression profiles of wild-type and mutant clones were compared by oligonucleotide expression microarray analysis. Firstly, clustering analysis classified the RTT patients according to their genetic background and MECP2 mutation. Secondly, expression profiling by microarray analysis and quantitative RT-PCR indicated four up-regulated genes and five down-regulated genes significantly dysregulated in all our statistical analysis, including excellent potential candidate genes for the understanding of the pathophysiology of this neurodevelopmental disease. Thirdly, chromatin immunoprecipitation analysis confirmed MeCP2 binding to respective CpG islands in three out of four up-regulated candidate genes and sequencing of bisulphite-converted DNA indicated that MeCP2 preferentially binds to methylated-DNA sequences. Most importantly, the finding that at least two of these genes (BMCC1 and RNF182) were shown to be involved in cell survival and/or apoptosis may suggest that impaired MeCP2 function could alter the survival of neurons thus compromising brain function without inducing cell death.

Cholestasis is a marker for hepatocellular carcinomas displaying beta-catenin mutations.

The Wnt/beta-catenin signalling pathway is activated in many human hepatocellular carcinomas (HCC). Identification of beta-catenin mutation relies mostly on sequence analysis and/or immunohistochemistry. beta-catenin mutation may also be detected by analysing the expression of its target genes. The GLUL gene encoding glutamine synthetase (GS), for example, appears to be a pertinent marker. The aim of this study was to correlate GS immunostaining and beta-catenin mutations with clinicopathological features in HCC. We found that GS immunostaining had a sensitivity of 90% for the detection of beta-catenin mutations, with 98% specificity, whereas beta-catenin immunostaining had a sensitivity of 63% with 98% specificity. We used the sensitive GS marker to characterize 190 HCC cases. Sixty-eight (36%) cases displayed Wnt/beta-catenin activation. In addition to their well-differentiated pattern, these tumours exhibited significant features such as a homogeneous microtrabeculo-acinar pattern, low-grade cellular atypia, and cholestasis. As these tumours exhibited cholestasis, we hypothesized that beta-catenin acts on specific bile synthesis and/or transport pathways. In conclusion, we propose that GS immunostaining and a cholestatic pattern are relevant criteria for the identification of HCC with beta-catenin mutations.

DNA microarray allows molecular profiling of rheumatoid arthritis and identification of pathophysiological targets.

This study was undertaken to evaluate the possibility to obtain a molecular signature of rheumatoid arthritis (RA) comparatively osteoarthritis (OA), and to lay the bases to develop new diagnostic tools and identify new targets. Microarray technology was used for such an analysis. The gene expression profiles of synovial tissues from patients with confirmed RA, and patients with OA were established and compared. A set of 63 genes was selected, based, more specifically, on their overexpression or underexpression in RA samples compared to OA. Results for six of these genes have been verified by quantitative PCR using both samples identical to those used in the microarray experiments and entirely separate samples. Expression profile of the 48 known genes allowed the correct classification of additional RA and OA patients. Furthermore, the distinct expression of three of the selected genes was also studied by quantitative RT-PCR in cultured synovial cells. Detailed analysis of the expression profile of the selected genes provided evidence for dysregulated biological pathways, pointed out to chromosomal location and revealed novel genes potentially involved in RA. It is proposed that such an approach allows valuable diagnosis/prognostics tools in RA to be established and potential targets for combating the disease to be identified.

Temporal loss of Nef-epitope CTL recognition following macaque lipopeptide immunization and SIV challenge.

To address the subtle interactions between antiviral cytotoxic T-cell (CTL) immune responses and the evolution of viral quasispecies variants in vivo, we performed a longitudinal study in a simian immunodeficiency virus (SIV)-infected rhesus macaque that had a long experimental SIV infection before developing simian AIDS. Before being infected with SIV, this animal was immunized with a mixture of seven lipopeptides derived from SIV Nef and Gag proteins and showed a bispecific antiviral CTL response directed toward Nef 169-178 and 211-225 peptides. After SIV infection, CTL activity against the Nef 169-178 epitope was no longer detectable, as assessed from peripheral blood mononuclear cells stimulated by autologous SIV. CTL activity against the 211-225 epitope was lost after 3 months, and an additional CTL response to the amino acids 112-119 Nef epitope emerged. Analysis of the Nef proviral sequence revealed the presence of immune escape variants first in the 211-225 epitope and much later in the 112-119 epitope. In contrast, epitope 169-178 showed only two mutations among all viral sequencing performed. We conclude that in this macaque, bispecific CTL exerted a strong selective pressure and escape virus mutants finally emerged. We identified CTL recognizing a conserved Nef epitope 112-119 (SYKLAIDM), essential for viral replication, which could be associated with a prolonged AIDS-free period. These results stress the importance of the induction of broader multispecific CTLs directed against highly conserved and functional T-cell epitopes by vaccination, with the aim of keeping HIV infection in check.

Increase of HIV-1 subtype A in Central African Republic.

The concomitant presence of five distinct HIV-1 subtypes and of unclassified HIV-1 was reported in Bangui, Central African Republic (C.A.R.) between 1990 and 1991. This previous study was conducted in individuals belonging to the C.A.R. Armed Forces (FACA) Cohort and in patients from the University Hospital of Baugui. To follow the HIV-1 subtype distribution in Bangui over time, we conducted a cross-sectional surveillance of HIV-1 subtypes between 1987 and 1997 in three groups of individuals in Bangui: 47 men belonging to the FACA Cohort, 38 patients from the CNHUB hospital, and 51 individuals consulting the sexually transmitted diseases (STD) clinic. One hundred and ten HIV-1 were subtyped by heteroduplex mobility assay (HMA) and/or sequencing of env regions encompassing the V3 domain. By comparing the HIV-1 distribution in two time periods (1987-1991 and 1991-1996) in the FACA cohort, we observed a significant increase of subtype A from 43.7% to 83.9%. This subtype distribution does not seem specific to the FACA cohort, in that subtype A accounted for 46.7% of the HIV-1 infections in CNHUB patients in the first time period studied and for 69.6% in the second time period. In STD patients, subtype A infections were predominant in 1995 (72.7%) and 1997 (89.7%). Subtype E viruses could be identified in the second time period, but represented only between 6.5% and 21.8% of the infections in the three groups of individuals studied. Other subtypes (B, C, H) and non-classified HIV-1 in C2-V3 were detected with only a 3.2% to 9.1% frequency for each in the second time period. Phylogenetic analysis excluded infection by a single source for the individuals included in the study. Our data demonstrate an increase in the proportion of HIV-1 subtype A infections in Bangui that raises the question of a preferential transmissibility of specific HIV-1 variants.

Cross-reactions between the cytotoxic T-lymphocyte responses of human immunodeficiency virus-infected African and European patients.

The great variability of protein sequences from human immunodeficiency virus (HIV) type 1 (HIV-1) isolates represents a major obstacle to the development of an effective vaccine against this virus. The surface protein (Env), which is the predominant target of neutralizing antibodies, is particularly variable. Here we examine the impact of variability among different HIV-1 subtypes (clades) on cytotoxic T-lymphocyte (CTL) activities, the other major component of the antiviral immune response. CTLs are produced not only against Env but also against other structural proteins, as well as some regulatory proteins. The genetic subtypes of HIV-1 were determined for Env and Gag from several patients infected either in France or in Africa. The cross-reactivities of the CTLs were tested with target cells expressing selected proteins from HIV-1 isolates of clade A or B or from HIV type 2 isolates. All African patients were infected with viruses belonging to clade A for Env and for Gag, except for one patient who was infected with a clade A Env-clade G Gag recombinant virus. All patients infected in France were infected with clade B viruses. The CTL responses obtained from all the African and all the French individuals tested showed frequent cross-reactions with proteins of the heterologous clade. Epitopes conserved between the viruses of clades A and B appeared especially frequent in Gag p24, Gag p18, integrase, and the central region of Nef. Cross-reactivity also existed among Gag epitopes of clades A, B, and G, as shown by the results for the patient infected with the clade A Env-clade G Gag recombinant virus. These results show that CTLs raised against viral antigens from different clades are able to cross-react, emphasizing the possibility of obtaining cross-immunizations for this part of the immune response in vaccinated individuals.

Complete nucleotide sequence of an African human T-lymphotropic virus type II subtype b isolate (HTLV-II-Gab): molecular and phylogenetic analysis.

We report the first complete nucleotide sequence of an African human T-cell lymphotropic virus type II. This new strain, called HTLV-II-Gab (Gab), was obtained from the uncultured peripheral blood mononuclear cells of a 44-year-old healthy Gabonese male who lived in a remote rural area, with neither history of blood transfusion nor sexual intercourse with non-Africans. Using nested PCR, 25 overlapping fragments, representing the entire proviral genome, were obtained, cloned and sequenced. The overall nucleotide sequence comparison with the four other available complete HTLV-II genomes indicated that Gab was more closely related to the HTLV-II subtype b prototypes (98.9, 99.3 and 98.2% nucleotide similarity with G12, NRA and GU respectively) than to the subtype a prototype (95.1% nucleotide similarity with Mo). Restriction profiles studies and phylogenetic analyses confirmed that Gab was a subtype b strain. However, this strain represents a newly described restriction fragment length polymorphism subtype, closely related to one of the rare partially sequenced African isolates originating from a pygmy living in Cameroon (PYGCAM). Nevertheless, the very low genetic divergence observed between this new African strain and the American strains raises several questions on the origins and level of genetic variability over time of this human retrovirus.

Susceptibility of human immunodeficiency virus type 1 group O isolates to antiretroviral agents: in vitro phenotypic and genotypic analyses.

We investigated the phenotypic and genotypic susceptibility of 11 human immunodeficiency virus type 1 (HIV-1) group O strains to nucleoside and nonnucleoside reverse transcriptase (RT) inhibitors and protease inhibitors in vitro. Phenotypic susceptibility was determined by using a standardized in vitro assay of RT inhibition, taking into account the replication kinetics of each strain. HIV-1 group M and HIV-2 isolates were used as references. DNA from cocultured peripheral blood mononuclear cells was amplified by using pol-specific group O primers and cloned for sequencing. Group O isolates were highly sensitive to nucleoside inhibitors, but six isolates were naturally highly resistant to all of the nonnucleoside RT inhibitors tested. Phylogenetic analysis of the pol gene showed that these isolates formed a separate cluster within group O, and genotypic analysis revealed a tyrosine-to-cysteine substitution at residue 181. Differences in susceptibility to saquinavir and ritonavir (RTV) were not significant between group O and group M isolates, although the 50% inhibitory concentration of RTV for group O isolates was higher than that for the HIV-1 subtype B strains. The study of HIV-1 group O susceptibility to antiretroviral drugs revealed that the viruses tested had specific phenotypic characteristics contrasting with the group M phenotypic expression.

In vivo longitudinal analysis of a dominant TCR repertoire selected in human response to influenza virus.

Recent studies have demonstrated biased usage of TCR V beta 17 and a high degree of diversity in J beta usage within the influenza virus matrix epitope (M.58-66)-specific CTL response. In contrast, in the course of a study on the cellular response to influenza A virus, we found preferential usage of V beta 17-J beta 2.2 rearrangement in an individual with an unexpectedly high number of CTL precursors (CTLp). We took advantage of such situation to study the longitudinal repertoire of the CD8+ T cell precursors. By limiting dilution analysis combined with the use of a clonotypic primer corresponding to the CDR3 region of this matrix-specific TCR V beta chain, the influenza-specific CTLp were shown to be stable for a period of 6 years. Overall, our results show that virus-specific CTLp can be directly monitored in vivo by molecular fingerprinting without in vitro restimulation. These findings might be extremely important for evaluation of the specific immune response to a given human pathogen.

Bridging Ral GTPase to Rho pathways. RLIP76, a Ral effector with CDC42/Rac GTPase-activating protein activity.

Ra1A and Ra1B are GTPases of unknown function and are activated by proteins, Ra1GDS, that interact with the active form of another GTPase, Ras. To elucidate Ral function, we have searched for proteins interacting with an activated form of Ra1A using the two-hybrid method and a Jurkat cell library. We have identified a partial cDNA encoding a protein, RLIP1, which binds to activated Ra1A and this binding requires an intact effector domain of Ra1A. Biochemical data with purified Ra1A confirm the genetic results. This protein also bears a region of homology with GTPase-activating protein (GAP) domains that are involved in the regulation of GTPases of the Rho family and, indeed, RLIP1 displays a GAP activity acting upon Rac1 and CDC42, but not RhoA. This GAP region is not required for RLIP1 binding to Ra1. The whole cDNA was cloned, and it encodes a 76-kDa polypeptide, RLIP76, which also binds RalA. The Rho pathway is involved in membrane and cytoskeleton modifications after mitogenic stimulation and acts in parallel to and synergistically with the Ras pathway. We propose that these pathways are linked through a cascade composed of Ras --> Ra1GDS --> Ra1 --> RLIP76 --> CDC42/Rac1/Rho, allowing modulation of the Rho pathway by the Ras pathway.

Variability of human immunodeficiency virus type 1 group O strains isolated from Cameroonian patients living in France.

Human immunodeficiency virus type 1 (HIV-1) nucleotide sequences encoding p24Gag and the Env C2V3 region were obtained from seven patients who were selected on the basis of having paradoxical seronegativity on a subset of HIV enzyme-linked immunosorbent assay detection kits and having atypical Western blot (immunoblot) reactivity. Sequence analyses showed that all of these strains were more closely related to the recently described Cameroonian HIV isolates of group O (HIV-1 outlier) than to group M (HIV-1 major). All seven patients had Cameroonian origins but were living in France at the time the blood samples were taken. Characterization of a large number of group M strains has to date revealed eight distinct genetic subtypes (A to H). Genetic distances between sequences from available group O isolates were generally comparable to those observed in M intersubtype sequence comparisons, showing that the group O viruses are genetically very diverse. Analysis of sequences from these seven new viral strains, combined with the three previously characterized group O strains, revealed few discernable phylogenetic clustering patterns among the 10 patients' viral sequences. The level of diversity among group O sequences suggests that they may have a comparable (or greater) age than the M group sequences, although for unknown reasons, the latter group dispersed first and is the dominant lineage in the pandemic.

Distinct functions of the Fc epsilon R1 gamma and beta subunits in the control of Fc epsilon R1-mediated tyrosine kinase activation and signaling responses in RBL-2H3 mast cells.

In RBL-2H3 rat tumor mast cells, cross-linking the high affinity IgE receptor, Fc epsilon R1, activates the protein-tyrosine kinases Lyn and Syk and initiates a series of responses including protein-tyrosine phosphorylation, inositol 1,4,5-trisphosphate synthesis, Ca2+ mobilization, secretion, membrane ruffling, and actin plaque assembly. The development of chimeric receptors containing cytoplasmic domains of individual subunits of the heterotrimeric (alpha beta gamma 2) Fc epsilon R1 has simplified analyses of early signaling events in RBL-2H3 cells. Here, RBL-2H3 cells were transfected with cDNAs encoding the extracellular and transmembrane domains of the interleukin-2 receptor alpha subunit (the Tac antigen) joined to the C-terminal cytoplasmic domains of the Fc epsilon R1 gamma and beta subunits (TT gamma and TT beta). Both sequences contain tyrosine activation motifs implicated in antigen receptor signal transduction. TT gamma and TT beta are expressed independently of the native Fc epsilon R1, as demonstrated by the ability of Tac cross-linking agents to trigger the clustering and internalization through coated pits of both chimeric receptors without co-clustering the Fc epsilon R1. A full range of signaling activities is induced by TT gamma cross-linking; the TT gamma-induced responses are slower and, except for Lyn activation, smaller than the Fc epsilon R1-induced responses. In striking contrast, TT beta cross-linking elicits no tyrosine phosphorylation or signaling responses, it impairs basal activities measured in secretion and anti-PY (anti-phosphotyrosine antibody) immune complex kinase assays, and it antagonizes Fc epsilon R1-induced Lyn and Syk activation, protein-tyrosine phosphorylation, and signaling responses. We hypothesize that the isolated beta subunit binds a specific kinase or coupling protein(s) required for signaling activity, sequestering it from the signal-transducing gamma subunit. Binding the same kinase or coupling protein to the beta subunit of the intact Fc epsilon R1 may serve instead to present it to the adjacent gamma subunit, resulting in enhanced kinase activation and signaling responses.

Analysis of human VH gene repertoire expression in peripheral CD19+ B cells.

Using CD19 B-cell selection and polymerase chain reaction-amplified cDNA libraries, we analyzed the peripheral immunoglobulin heavy chain variable repertoire of three healthy adult donors. Here we report that most of the CD19+ circulating B cells expressed unmutated VH-D-JH rearrangements. By specific VH family hybridization, we show that VH gene family utilization in the periphery roughly corresponds to the complexity of these families in the germline and appears to be relatively constant among the analyzed subjects. However, sequence data of clones picked at random from one IgM cDNA library reveals that in spite of this "random" utilization, the VH gene expression in naive circulating B cells is highly biased towards the expression of a limited set of VH genes. As previously reported by others, this restricted mechanism is also found for the D and JH segments.

Interactions of p59fyn and ZAP-70 with T-cell receptor activation motifs: defining the nature of a signalling motif.

The tyrosine-based activation motif is a 20- to 25-amino-acid sequence contained in the cytoplasmic domains of many hematopoietic receptors which is sufficient by itself to reconstitute signalling. This motif is characterized by two YXXL/I sequences separated by approximately 10 residues. The molecular basis of signalling by this motif is unknown. Here we demonstrate that the tyrosine-based activation motif is required and sufficient for association with the tyrosine kinases p59fyn and ZAP-70, suggesting that association with these kinases is a general feature of this motif. Focusing on the single activation motif present in epsilon, we analyzed which residues of the motif were critical for binding of p59fyn and ZAP-70. Surprisingly, we found that no single mutation of any residue of epsilon resulted in the loss of p59fyn association. In contrast, single mutations at five residues of the epsilon activating motif abrogated ZAP-70 binding. Both of the tyrosines and the leucine or isoleucine residues that follow them were critical. The spacing between the tyrosines was also important, as deletion of two residues disrupted binding of ZAP-70, although p59fyn binding was not disrupted. Most of the defined features of the tyrosine activation motif are therefore requirements for ZAP-70 binding. Interestingly, the interaction of ZAP-70 with the motif was dependent on the presence of both ZAP-70 SH2 domains and both of the tyrosine residues in the motif, suggesting that ZAP-70 interacts with two phosphotyrosine residues and that the binding of the two SH2 domains is cooperative. In addition, we demonstrate that the interaction between the tyrosine activation motif is direct and requires prior tyrosine phosphorylation of the motif. We propose that the activation of cells by the tyrosine activating motif occurs in four discrete steps: binding of p59fyn, phosphorylation of the motif, binding of ZAP-70, and activation of ZAP-70 kinase activity.

Coatomer interaction with di-lysine endoplasmic reticulum retention motifs.

Although signals for retention in the endoplasmic reticulum (ER) have been identified in the cytoplasmic domain of various ER-resident type I transmembrane proteins, the mechanisms responsible for ER retention are still unknown. Yeast and mammalian ER retention motifs interacted specifically in cell lysates with the coatomer, a polypeptide complex implicated in membrane traffic. Mutations that affect the ER retention capacity of the motifs also abolished binding of the coatomer. These results suggest a role for the coatomer in the retrieval of transmembrane proteins to the ER in both yeast and mammals.

Role of CD3 delta in surface expression of the TCR/CD3 complex and in activation for killing analyzed with a CD3 delta-negative cytotoxic T lymphocyte variant.

The TCR is composed of two chains (alpha/beta) containing variable regions associated at the cell surface with invariant chains (CD3 gamma-, delta-, epsilon-, and zeta/eta chains). The latter control assembly and surface expression of the TCR/CD3 complex, as well as its cytoplasmic association with signal transduction relays. In differentiated CTL, stimulation through the TCR leads to the transcriptional activation of genes coding secreted cytokines such as gamma-IFN as well as transcription-independent activation of the lytic machinery. It is not known which of the CD3 components is necessary to transduce the required signals. CD3 gamma- and delta-chains have high sequence homology, in particular in their cytoplasmic domain, and it has been proposed that alpha beta gamma epsilon zeta and alpha beta delta, epsilon zeta may be expressed and function in signal transduction independently. Here, we characterize a CTL clone that has selectively lost expression of the CD3 delta mRNA. This results in expression of partial CD3 complexes devoid of TCR alpha beta chains at the surface of the clone, which are not functional for activation of cytolysis or for gamma-IFN production. Transfection of the clone with either the native or a cytoplasmic exon-deleted CD3 delta gene restores full TCR/CD3 surface expression as well as Ag- or CD3-mediated activation for killing and for gamma-IFN production, indicating that the CD3 delta chain is essential for surface expression of the TCR alpha beta, but that the CD3 delta cytoplasmic portion is not required either for complex assembly or for signal transduction involved in the functions studied.

CD3 zeta dependence of the CD2 pathway of activation in T lymphocytes and natural killer cells.

In T lymphocytes, signal transduction through the CD2 adhesion molecule requires surface expression of the CD3-Ti T-cell receptor (TCR) complex. In contrast, in natural killer (NK) cells, CD2 functions in the absence of a TCR. Because the TCR on T lymphocytes and the CD16 low-affinity IgG Fc receptor (Fc gamma receptor type III) complex on NK cells share a common CD3 zeta subunit, we reasoned that CD3 zeta may be critical for CD2 signaling in T lymphocytes and NK cells. Here we show that transfection of a cDNA encoding a transmembrane form of CD16 into TCR- variants of the Jurkat T-cell line results in CD16 expression in association with endogenous CD3 zeta homodimers and restores CD2 signaling function. To test directly the role of CD3 zeta in CD2 triggering, we then transfected human CD2 into each of two murine T-T hybridomas that express TCRs containing either a full-length CD3 zeta subunit or a truncated CD3 zeta subunit incapable of transducing signals. Despite expression of equivalent surface levels of TCR, CD2-mediated signaling is seen only in the T cells containing wild-type CD3 zeta. These findings show that (i) CD16 on NK cells is functionally equivalent to the TCR on T lymphocytes for coupling CD2 to signaling pathways and (ii) CD2 signal transduction depends upon the CD3 zeta subunit of the TCR complex and, by inference, the CD3 zeta subunit of the CD16 complex.

The T cell receptor/CD3 complex is composed of at least two autonomous transduction modules.

Recent studies have demonstrated that the CD3-zeta subunit of the T cell antigen receptor (TCR) complex is involved in signal transduction. However, the function of the remaining invariant subunits, CD3-gamma, -delta, and epsilon, is still poorly understood. To examine their role in TCR function, we have constructed TCR/CD3 complexes devoid of functional zeta subunit and showed that they are still able to trigger the production of interleukin-2 in response to antigen or superantigen. These data, together with previous results, indicate that the TCR/CD3 complex is composed of at least two parallel transducing units, made of the gamma delta epsilon and zeta chains, respectively. Furthermore, the analysis of partially truncated zeta chains has led us to individualize a functional domain that may have constituted the building block of most of the transducing subunits associated with antigen receptors and some Fc receptors.