Biomedical subjects

C Brander

Publications and source records attributed to C Brander.

At least 37 records · Page 2Linked to original sources

PubMed2000

Efficient generation of human T cells from a tissue-engineered thymic organoid.

Biocompatible inorganic matrices have been used to enhance bone repair by integrating with endogenous bone architecture. Hypothesizing that a three-dimensional framework might support reconstruction of other tissues as well, we assessed the capacity of a tantalum-coated carbon matrix to support reconstitution of functioning thymic tissue. We engineered a thymic organoid by seeding matrices with murine thymic stroma. Co-culture of human bone marrow-derived hematopoietic progenitor cells within this xenogeneic environment generated mature functional T cells within 14 days. The proportionate T-cell yield from this system was highly reproducible, generating over 70% CD3+ T cells from either AC133+ or CD34+ progenitor cells. Cultured T cells expressed a high level of T-cell receptor excision circles (TREC), demonstrating de novo T lymphopoiesis, and function of fully mature T cells. This system not only facilitates analysis of the T-lymphopoietic potential of progenitor cell populations; it also permits ex vivo genesis of T cells for possible applications in treatment of immunodeficiency.

AC133 Antigen↗

PubMed2000

Differential narrow focusing of immunodominant human immunodeficiency virus gag-specific cytotoxic T-lymphocyte responses in infected African and caucasoid adults and children.

Cytotoxic T-lymphocyte (CTL) activity plays a central role in control of viral replication and in determining outcome in cases of human immunodeficiency virus type 1 (HIV-1) infection. Incorporation of important CTL epitope sequences into candidate vaccines is, therefore, vital. Most CTL studies have focused upon small numbers of adult Caucasoid subjects infected with clade-B virus, whereas the global epidemic is most severe in sub-Saharan African populations and predominantly involves clade-C infection in both adults and children. In this study, sensitive enzyme-linked immunospot (elispot) assays have been utilized to identify the dominant Gag-specific CTL epitopes targeted by adults and children infected with clade-B or -C virus. Cohorts evaluated included 44 B-clade-infected Caucasoid American and African American adults and children and 37 C-clade-infected African adults and children from Durban, South Africa. The results show that 3 out of 46 peptides spanning p17(Gag) and p24(Gag) sequences tested contain two-thirds of the dominant Gag-specific epitopes, irrespective of the clade, ethnicity, or age group studied. However, there were distinctive differences between the dominant responses made by Caucasoids and Africans. Dominant responses in Caucasoids were more often within p17(Gag) peptide residues 16 to 30 (38 versus 12%; P < 0.01), while p24(Gag) peptide residues 41 to 60 contained the dominant Gag epitope more often in the African subjects tested (39 versus 4%; P < 0.005). Within this 20-mer p24(Gag), an epitope presented by both B42 and B81 is defined which represents the dominant Gag response in >30% of the total infected population in Durban. This epitope is closely homologous with dominant HIV-2 and simian immunodeficiency virus Gag-specific CTL epitopes. The fine focusing of dominant CTL responses to these few regions of high immunogenicity is of significance to vaccine design.

Adult↗

PubMed1999

Persistent HIV-1-specific CTL clonal expansion despite high viral burden post in utero HIV-1 infection.

To address the issue of clonal exhaustion in humans, we monitored HLA class I-restricted, epitope-specific CTL responses in an in utero HIV-1-infected infant from 3 mo through 5 years of age. Serial functional CTL precursor assays demonstrated persistent, vigorous, and broadly directed HIV-1 specific CTL activity with a dominant response against an epitope in HIV-1 Gag-p17 (SLYNTVATL, aa 77-85). A clonal CTL response directed against the immunodominant, HLA-A*0201-restricted epitope was found to persist over the entire observation period, as shown by TCR analysis of cDNA libraries generated from PBMC. The analysis of autologous viral sequences did not reveal any escape mutations within the targeted epitope, and viral load measurement indicated ongoing viral replication. Furthermore, inhibition of viral replication assays indicated that the epitope was properly processed from autologous viral protein. These data demonstrate that persistent exposure to high levels of viral Ag does not necessarily lead to clonal exhaustion and that epitope-specific clonal CTL responses induced within the first weeks of life can persist for years without inducing detectable viral escape variants.

Child, Preschool↗

PubMed1999

T lymphocyte responses in HIV-1 infection: implications for vaccine development.

Substantial progress has been made over the past year in understanding the cellular immune response in HIV pathogenesis. Cytotoxic T lymphocytes play a critical role in establishing the level of viremia and virus-specific Th cell responses appear to affect the in vivo efficacy of cytotoxic T lymphocytes. Together, these new data provide important insights to refocus efforts aimed at immunotherapeutic interventions and vaccine development.

AIDS Vaccines↗

PubMed1999

Efficient processing of the immunodominant, HLA-A*0201-restricted human immunodeficiency virus type 1 cytotoxic T-lymphocyte epitope despite multiple variations in the epitope flanking sequences.

Immune escape from cytotoxic T-lymphocyte (CTL) responses has been shown to occur not only by changes within the targeted epitope but also by changes in the flanking sequences which interfere with the processing of the immunogenic peptide. However, the frequency of such an escape mechanism has not been determined. To investigate whether naturally occurring variations in the flanking sequences of an immunodominant human immunodeficiency virus type 1 (HIV-1) Gag CTL epitope prevent antigen processing, cells infected with HIV-1 or vaccinia virus constructs encoding different patient-derived Gag sequences were tested for recognition by HLA-A*0201-restricted, p17-specific CTL. We found that the immunodominant p17 epitope (SL9) and its variants were efficiently processed from minigene expressing vectors and from six HIV-1 Gag variants expressed by recombinant vaccinia virus constructs. Furthermore, SL9-specific CTL clones derived from multiple donors efficiently inhibited virus replication when added to HLA-A*0201-bearing cells infected with primary or laboratory-adapted strains of virus, despite the variability in the SL9 flanking sequences. These data suggest that escape from this immunodominant CTL response is not frequently accomplished by changes in the epitope flanking sequences.

Adolescent↗

PubMed1998

Lack of strong immune selection pressure by the immunodominant, HLA-A*0201-restricted cytotoxic T lymphocyte response in chronic human immunodeficiency virus-1 infection.

Despite detailed analysis of the HIV-1-specific cytotoxic T lymphocyte response by various groups, its relation to viral load and viral sequence variation remains controversial. We analyzed HLA-A*0201 restricted cytotoxic T lymphocyte responses in 17 HIV-1-infected individuals with viral loads ranging from < 400 to 221,000 HIV RNA molecules per milliliter of plasma. In 13 out of 17 infected subjects, CTL responses against the SLYNTVATL epitope (p17 Gag; aa 77-85) were detectable, whereas two other HLA-A*0201 restricted epitopes (ILKEPVHGV, IV9; and VIYQYMDDL, VL9) were only recognized by six and five individuals out of 17 individuals tested, respectively. Naturally occurring variants of the SL9 epitope were tested for binding to HLA-A*0201 and for recognition by specific T cell clones generated from five individuals. Although these variants were widely recognized, they differed by up to 10,000-fold in terms of variant peptide concentrations required for lysis of target cells. A comparison of viral sequences derived from 10 HLA-A*0201-positive individuals to sequences obtained from 11 HLA-A*0201-negative individuals demonstrated only weak evidence for immune selective pressure and thus question the in vivo efficacy of immunodominant CTL responses present during chronic HIV-1 infection.

Acquired Immunodeficiency Syndrome↗

PubMed1997

Characterization of lidocaine-specific T cells.

To investigate the cellular immune response to the drug lidocaine, we generated T cell lines and clones from the peripheral blood of four patients with proven allergy to lidocaine. The patients had contact dermatitis after topical application of lidocaine, and local swelling or generalized erythema exudativum multiforme after submucosal/subcutaneous injection of lidocaine. Two of three lidocaine-specific T cell lines were oligoclonal and one even became monoclonal, while the simultaneously analyzed immune response to tetanus toxoid was polyclonal. The lidocaine-specific T cell lines cross-reacted to mepivacaine, but not to other local anesthetics (bupivacaine, procaine, oxybuprocaine, and tetracaine). The majority of reactive T cells belonged to the CD4 cell lineage and were MHC class II restricted, but cloning also revealed some MHC class I-restricted CD8+ clones. A total of 2 of 56 lidocaine-specific T cell clones were CD4-CD8- and expressed TCR-gammadelta. The majority of 13 analyzed CD4 clones produced a rather polarized cytokine pattern, with a dominance of Th2-like cytokines showing a high IL-5 production. In addition, three CD4+ and all CD8+ (n = 7) clones secreted high IFN-gamma and low levels of IL-5/IL-4 (Th1-like). The data illustrate that a drug that sensitizes via the skin elicits a heterogeneous T cell response. The high IL-5 production and the participation of specific CD4+CD8+ and even gammadelta+ T cells appear to be distinguishing features of this hapten-specific immune response.

Adult↗

PubMed1997

Stimulation of human cytotoxic T cells with HIV-1-derived peptides presented by recombinant HLA-A2 peptide complexes.

HLA-A2 heavy chain and beta 2-microglobulin were expressed in Escherichia coli, and refolded in the presence of peptides derived from HIV-1 RT and gag proteins. When recombinant HLA-A2 molecules were attached to cells lacking HLA-A2, the cells became susceptible to lysis by HLA-A2-restricted cytotoxic T lymphocyte (CTL) clones specific for peptides derived from RT and gag proteins. Limiting dilution analyses of peripheral blood mononuclear cells from HIV-1-infected individuals showed that the recombinant HLA-A2 peptide complexes covalently immobilized on microspheres stimulated the development of HLA-A2 peptide-specific CTL. Preformed HLA-peptide complexes may provide an alternative to immunization procedures that depend upon intracellular processing of antigen to elicit T cell responses.

Antigen Presentation↗

PubMed1996

Cross-reactivity of T cell lines and clones to beta-lactam antibiotics.

To clarify on a molecular level the specific T cell response to haptens like penicillin G, we generated T cell lines and clones from penicillin-allergic patients. Two types of beta-lactam reactivity of T cells could be delineated: one group of patients showed a rather restricted specificity, as the penicillin-elicited T cell lines generated from such donors proliferated only to the stimulating penicillin, but not to other beta-lactam antibiotics nor to cephalosporines, even if the side chain was identical. This indicates that the penicilloyl structure together with the side chain was recognized by these T cells. The second group comprised patients with more broadly reactive T cells, as they were restimulated by penicillin G as well as by related penicillins like amoxicillin or ampicillin, but not cephalosporines. This indicates that the penicilloyl structure, a common motif of penicillins, was important for T cell recognition. Clones generated from a broadly reactive patient confirmed this heterogeneity, as either monospecific or broadly specific T cell clones could be identified. This broad or very restricted pattern of T cell reactivity was reflected in the use of TCR Vbeta-chains: while the broadly reactive T cell lines showed a heterogenous TCR usage, the highly restricted T cell lines showed an up-regulation of one TCR Vbeta-chain. Thus, our data suggest that the outgrowth of T cells bearing a certain TCR Vbeta may be a sign of a limited cross-reactivity.

Anti-Bacterial Agents↗

PubMed1996

Peptide immunization in humans: a combined CD8+/CD4+ T cell-targeted vaccine restimulates the memory CD4 T cell response but fails to induce cytotoxic T lymphocytes (CTL).

Immunization with short antigenic peptides represents a potential strategy to induce peptide-specific CTL in vivo. In this study, a synthetic vaccine consisting of an HIV-derived, HLA-A2.1-binding CTL epitope and a tetanus toxin-derived T helper epitope was evaluated for its capacity to induce peptide-specific CTL in humans. Thirteen volunteers were immunized and boosted twice with 100 micrograms of the CTL epitope plus 300 micrograms of the T helper peptide (p30). Peripheral blood mononuclear cells (PBMC) were regularly analysed for cytotoxic and proliferative responses before, between and after the immunizations, and the serum was tested for anti-peptide antibodies. No unequivocal induction of HIV peptide-specific CTL in any of the volunteers was observed. However, a wide pattern of mild and transient side reactions was observed, ranging from local redness at the injection site to generalized exanthema, myalgias, arthralgias and fever. The side-effects were related to the T helper epitope, as they were similar to the side-effects experienced after tetanus immunization, correlated to the magnitude of the p30-specific in vitro proliferative response, and occurred only if p30 was co-injected. No antibodies against the HIV-derived peptides nor against p30 were detectable in the serum after repeated immunizations. The data suggest that the CTL peptide, at the concentration used in this study, failed to induce a cytotoxic immune response in vivo, although the T helper peptide seems to be capable of restimulating the specific memory T cells.

Animals↗

PubMed1996

T cell reactions in patients showing adverse immune reactions to drugs.

OBJECTIVE AND DESIGN: To better understand how T cells react to small compounds, we investigated the in vitro T cell reactivity to drugs from drug allergic patients. MATERIAL AND SUBJECTS: Peripheral blood mononuclear cells (PBMC) of three drug allergic individuals were stimulated in vitro by different drugs. METHODS: Proliferation was assayed by 3H-thymidine incorporation. Upregulation of activation parameter on T cells was done by immunofluorescence and cytokine release determined via standard ELISA. RESULTS: Drugs can stimulate both CD4 and CD8 T-cell subsets. PenG-stimulated PBMC showed a heterogenous cytokine pattern and clones secreted high amounts of INF gamma. In contrast, sulfamethoxazole and lidocaine-stimulated PBMC secreted high levels of IL-5 and lidocaine-specific clones can be Th1 or Th2-like. CONCLUSION: Drug specific T cells play a pivotal role in drug hypersensitivity reactions, both by regulating the immune response and probably also as specific effector cells with different patterns of cytokine release.

Adult↗

PubMed1995

Heterogeneous T cell responses to beta-lactam-modified self-structures are observed in penicillin-allergic individuals.

To investigate the role of T cells in drug allergy, we stimulated PBMC from penicillin-allergic patients with reactive penicillin G itself or penicillin G coupled with human serum albumin (BPO-HSA). T cell clones specific for penicillin G or BPO-HSA were established and their phenotype and reactivity to both forms of the beta-lactam were analyzed. T cell clones stimulated by penicillin G were CD4 and CD8 positive, whereas BPO-HSA stimulated the growth of CD4+ T cells. The penicillin G-specific clones were HLA class I or class II restricted and processing was not required as fixed APC could still present penicillin G. In contrast, BPO-HSA has to undergo processing to stimulate BPO-HSA-specific T cell clones. In addition to classical APC, activated MHC class II expressing T cells could also restimulate the penicillin G-specific clones, indicating that various cell types might serve as APC. Penicillin G and BPO-HSA-specific T cell clones produced a heterogeneous cytokine pattern as most clones produced high amounts of IL-2, IFN-gamma, TFN-alpha, and rather variable levels of IL-4 and IL-5. Since no Ag processing was required, penicillin G may stimulate T cells by binding directly to MHC molecules on the cell surface or to their embedded peptide. Alternatively, it may bind to soluble proteins like HSA, which are processed and subsequently presented in an immunogenic form. These different modes of presentation, which elicit a variety of immunological reactivities, may explain the great heterogeneity of the clinical pictures seen in penicillin allergy.

Antigen Presentation↗

PubMed1995

Activation of drug-specific CD4+ and CD8+ T cells in individuals allergic to sulfonamides, phenytoin, and carbamazepine.

To investigate how T cells are involved in hypersensitivity reactions to drugs that become immunogenic after metabolization, e.g., sulfonamides and antiepileptics, we analyzed in vitro the drug-induced activation of CD4+ and CD8+ T cell subsets, cytokine secretion, TCR V beta distribution, and proliferation of T cells from four drug-allergic individuals. In addition, the activation parameters CD25 and HLA-DR were analyzed in vivo on CD4+ and CD8+ T cells from five patients with acute drug allergies, some of them with anticonvulsant hypersensitivity syndrome with hepatitis. Our results show that, in vitro, drug-induced proliferation of PBMC from patients with allergy to sulfamethoxazole, phenytoin, or carbamazepine was specific and dose dependent. CD4+ as well as CD8+ T cells expressed elevated levels of CD25 and HLA-DR molecules after drug stimulation. Drug-activated lymphocytes secreted high amounts of IL-5 and normal or low levels of IL-2, IFN-gamma, IL-4, and TNF-alpha. An enhanced expansion of TCR V beta 17+ T cells 9 days after in vitro stimulation with sulfamethoxazole was observed in one patient with sulfamethoxazole allergy. The drug specificity of the in vitro-activated T cells was confirmed by generation of different sulfamethoxazole specific T cell lines and CD4+ and CD8+ T cell clones. T cell analysis of patients with acute drug allergy to carbamazepine, phenytoin, allopurinol, or paracetamol confirms the in vitro data, because all patients had activated CD4+ or CD8+ T cells in the circulation. Our data clearly show the involvement of drug-specific T cells in drug allergies.

Anticonvulsants↗

PubMed1995

Identification of HIV protein-derived cytotoxic T lymphocyte (CTL) epitopes for their possible use as synthetic vaccine.

CTL are by far the most important defence mechanisms against viral infections, and many attempts have been undertaken to induce protective CTL in vivo. In order to identify CTL epitopes for their possible use as peptide-vaccine candidates, HIV proteins were screened for peptide sequences which (i) fulfil the binding motif of the HLA-A2.1 molecule, and (ii) are involved in the natural immune response to HIV. From 73 nonameric peptides satisfying the binding motif, 20 peptides were synthesized and their binding to HLA-A2.1 was monitored by measuring the expression of HLA-A2.1 molecules on the cell surface of the mutant cell line T2. To evaluate the involvement in natural HIV infection, strongly binding peptides were used in cytotoxicity assays to assess their capacity to generate a peptide-specific CTL response in vitro. From 20 nonameric peptides synthesized, only five showed strong binding to HLA-A2.1. All five binding peptides had the secondary anchor residues, recently proposed by Ruppert et al. [1] to be required for binding to HLA-A2.1. The discrimination between bound and unbound peptides confirmed the importance of these secondary anchor residues which, beside the known binding motif, may dictate if a peptide can bind to HLA-A2.1 or not. In HIV- donors, no CTL activity against any of the HIV-derived peptides was detectable after a 12-day in vitro stimulation. In contrast, HIV-infected persons showed a cytotoxic response against peptide-labelled target cells, suggesting that they had developed upon HIV infection a cytotoxic immune response against the identified CTL epitopes.

Amino Acid Sequence↗

PubMed1994

Improved sensitization of antigen-presenting cells with transferrin-bound peptides: advantages in competition for antigen presentation.

T cells recognize peptides in association with major histocompatibility complex (MHC) molecules on the surface of antigen-presenting cells (APC). To sensitize APC for antigen presentation in vitro and in vivo, high concentrations of synthetic peptides can be added from the outside and bind to the MHC molecules, thereby mimicking naturally processed peptides. In this report we investigated whether the transferrin (Tf) molecule could be used as a carrier to introduce antigenic peptides into the antigen presentation pathway of APC. We coupled to Tf various MHC class II DR1 restricted peptides and compared the sensitization of DR1+ APC by the Tf-bound or by the soluble peptide, using peptide-specific T cell clones (TCC). The presentation of the Tf-bound peptides was MHC restricted and could be blocked by the fixation of the APC with glutaraldehyde or by the addition of an excess of Tf. Tf-bound peptides were more efficiently presented than soluble peptides, since smaller concentrations were required to sensitize APC. Moreover, they could compete with a soluble peptide for MHC restricted presentation with a very high efficiency if compared to soluble competing peptides. Tf peptide conjugates could even compete with the presentation of a native antigen like tetanus toxoid. Peptides bound to the transferrin molecule might be useful for immunization strategies, as the relevant bound peptides are efficiently presented to peptide-specific TCC.

Antigen Presentation↗

PubMed1994

Peptide-induced T cell clones: specificity, MHC restriction, proliferation and cytokine pattern as a function of different stimulations.

CD4+ T cell clones were generated to tetanus toxin or to two tetanus toxin-derived peptides p2 (AA 830-834) and p30 (AA 947-976). 11 of the 24 p30-specific clones reacted to shorter p30 subunits (p301 or p302), and only 14 of the p2 or p30-specific clones reacted with TT presented by EBV-transformed B cell lines (B-LCL). The p30-specific clones were HLA-DP4 restricted. In contrast to autologous B cell lines, the majority of allogeneic, but HLA-DP4-positive cell lines failed to present p30 to the specific clones. We concluded that T cell clones are highly specific and that both, small alterations of the peptide length as well as discrete differences of the HLA-molecule may abrogate recognition of the peptide HLA complex by T cells. Moreover, use of peptides as stimulators of T cells may recruit and activate T cells which fail the "original" peptide, derived from normal antigen processing. Clones could usually be maintained in culture for 4-6 months, but with the help of freezing and thawing some clones are now available for over 2 years and still specific. Comparison of different autologous antigen-presenting cells, namely B-LCL and activated MHC class II-positive T cells revealed that not all clones were able to mount a proliferative response to peptide presentation by T cells, while all clones proliferated to B cells as APC. If stimulated with peptide and B-LCL, the clone proliferating to T cells as APC (so-called T responder clones) secreted a broad spectrum of cytokines (Th0-like) and were easier to maintain in culture. In contrast, clones which were unable to proliferate to peptide presentation, so-called T-nonresponder clones, showed a more restricted cytokine pattern and elevated or very low IL4/IFN gamma ratio upon antigen specific stimulation. However, all clones secreted at least small amounts of IL2, IL4, IFN gamma and TNF alpha, if stimulated by PMA and ionomycin. Thus, both chemical and antigen-specific stimulations should be considered if T cell clones are classified as Th1 or Th2, whereby those clones, which secrete a limited cytokine pattern after antigen stimulation only, might be named Th1 or Th2 like clones, while clones which even after PMA/ionomycin do not secrete all cytokines, might represent "real" Th1 or Th2 clones.

Clone Cells↗

PubMed1993

Carrier-mediated uptake and presentation of a major histocompatibility complex class I-restricted peptide.

Antigenic peptides derived from endogenous or viral proteins can associate with class I or class II major histocompatibility complex (MHC) molecules, while exogenous antigens are endocytosed, processed intracellularly and presented on MHC class II molecules. Here we describe a method that allows the presentation of an MHC class I-restricted antigenic peptide on MHC class I molecules, although it was taken up from the outside. The HLA-A2-restricted influenza virus matrix protein-derived peptide (flu, 57-68) was used either in soluble form or coupled via an S-S bridge to transferrin (Tf-flu). Target cells were incubated with flu or Tf-flu and the effective antigen presentation was detected in a cytotoxicity assay using flu peptide-specific, HLA-A2-restricted CD8+ cytotoxic T lymphocytes. Sensitization of target cells with Tf-flu required 5 to 10 times higher molar concentrations of peptide compared to sensitization with soluble free peptide. The Tf-flu construct was taken up by the cells via the Tf receptor (CD71) as the binding of Tf-flu was blocked by an excess of Tf. In contrast to the flu peptide, cytotoxicity elicited by Tf-flu was blocked by brefeldin A but not by chloroquine nor inhibitors of intracellular reducing steps, like 1-buthionine-(s,r)-sulfoximine or n-ethylmaleimide. Presentation of the flu peptide derived from Tf-flu construct is not hindered in the mutant T2 cell line, which lacks genes coding for transporter proteins for antigenic peptides (TAP1/TAP2) and proteasomes subunits, suggesting that the processing pathway described in this report may involve TAP-independent steps.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1992

Discrimination of human CD4 T cell clones based on their reactivity with antigen-presenting T cells.

In this report, we describe the discrimination of human T cell clones based on their reactivity with activated T cells as antigen-presenting cells (APC). CD4+ T cell clones specific for peptide P30 of tetanus toxin (amino acids 947-967) and restricted to the DP4 molecule were established and tested for proliferation to peptide presented either by peripheral blood mononuclear cells (PBMC), Epstein-Barr virus (EBV)-transformed B cells or major histocompatibility complex (MHC) class II-expressing T cells. We found two sets of T cell clones: one set proliferated to peptide presentation by PBMC, EBV-transformed B cell lines (EBV-B cells) and MHC class II+ T cells (termed T-responder clones), while the other set of clones was only stimulated to proliferate, if the peptide was presented by PBMC or EBV-B cells, but not by T cells (T-nonresponder clones). Nevertheless, these T-nonresponder clones recognized P30 also on T cells, as revealed by Ca2+ influx. The discrimination of the clones was not due to different avidities of the T cell receptors (TcR) of individual clones for the MHC-peptide complex as T-responder and T-nonresponder clones had similar dose-response curves to P30 presented by fixed EBV-B cell lines. Addition of cytokines [interleukin (IL)-1, IL-2, IL-4 and interferon gamma] did not change the proliferative response of the clones, which was consistent throughout an observation period of greater than 4 months. T-nonresponder clones, exposed to P30 on MHC class II-expressing T cells, became not anergic, as they could be restimulated by P30 presented on EBV-B cells. The measurement of a panel of T cell activation markers and adhesion molecules on T-responder and T-nonresponder clones revealed a higher expression of the CD28 molecule on the T-nonresponder clones. The data suggest that freshly cloned T cells can be differentiated by peptide presentation on classical (PBMC, EBV-B cells) or non-classical APC (class II+ T cells), and that this discrimination is further underlined by different levels of adhesion molecules.

Antigen-Presenting Cells↗