Characterization of the T-cell receptor Vbeta repertoire in the human immune response against Leishmania parasites

T-cell receptor variable region usage in Chagas disease: A systematic review of experimental and human studies

T cells recognize their ligand, the peptide major histocompatibility complex (MHC), via the T-cell receptor (TCR), which is composed of covalently linked α and β or γ and δ chains. This recognition is critical for T-cell ontogeny and controls the selection, activation, and function of T lymphocytes. Specific TCR αβ variable regions have been associated with immunopathogenesis of Chagas disease. Here, we present a systematic review that compiles experimental in vivo and human data regarding the preferential expression of variable alpha (Vα) and variable beta (Vβ) chain regions in Trypanosoma cruzi infection. The original studies indexed in PubMed/Medline, Scopus, and Web of Science databases were screened according to the PRISMA strategy. The analysis showed that expression of TCR Vα subfamilies were evaluated in one human study, and, unlike TCR Vβ, TCR Vα presented a more restricted usage. Despite the great variability in the usage of TCR Vβ regions in human Chagas disease, a down-regulation of TCR Vβ5 expression by T cells from patients in the acute phase of the disease was shown. Opposingly, this TCR region was found overly expressed in CD4+ T cells from chronic Chagas patients. It was also demonstrated that murine Vβ9+ T cells derived from nonlymphoid organs of T. cruzi-infected animals had a modulatory profile, while splenic Vβ9+ T cells produced inflammatory cytokines, indicating that although they display the same TCR Vβ region usage, these cells are functionally distinct. Despite the limitations of few papers and year of publication of the studies, compiling the data derived from them reveals that further investigation of TCR usage will point to their potential role in protective or pathogenic responses, as biomarkers of disease progression, and in the search for dominant peptides potentially useful for the development of vaccines or therapies.

Chagas disease is a neglected tropical disease, caused by infection with Trypanosoma cruzi. Differential expression of certain T-cell receptor (TCR) variable regions has been associated with the immunopathogenesis of Chagas disease. Here, we present a systematic review that compiled experimental in vivo and human data regarding the preferential expression of TCR alpha and beta chain variable regions in Chagas disease. The original studies indexed in the PubMed/Medline, Scopus, and Web of Science databases were screened according to the PRISMA strategy. Despite the great variability in the use of TCR Vβ in T. cruzi infection, the outcomes indicate that there is a down-regulation of TCR Vβ5 expression in T cells from patients in the acute phase of Chagas disease. However, this region is preferentially expressed by CD4+ T cells from chronic Chagas patients. Additionally, it has been demonstrated that murine Vβ9+ T cells derived from nonlymphoid organs displayed a modulatory profile, while splenic Vβ9+ T cells produced inflammatory cytokines, indicating that although they express the same TCR Vβ region, these cells are functionally distinct. Information on TCR expression, specificity and function have critical impact on vaccine design.

Impaired Thymic Output Can Be Related to the Low Immune Reconstitution and T Cell Repertoire Disturbances in Relapsing Visceral Leishmaniasis Associated HIV/AIDS Patients

Background: Visceral leishmaniasis/HIV-co-infected patients (VL/HIV) accounts for around 8% of VL reported cases in Brazil. Relapses of Leishmania infection after anti-leishmanial treatment constitute a great challenge in the clinical practice because of the disease severity and drug resistance. We have shown that non-relapsing-VL/HIV (NR-) evolved with increase of CD4⁺ T-cell counts and reduction of activated CD4⁺ and CD8⁺ T cells after anti-leishmanial treatment. This immune profile was not observed in relapsing-VL/HIV patients (R-), indicating a more severe immunological compromising degree. Elevated activation status may be related to a deficient immune reconstitution and could help to explain the frequent relapses in VL/HIV co-infection. Our aim was to evaluate if this gain of T cells was related to changes in the peripheral TCRVβ repertoire and inflammatory status, as well as the possible thymus involvement in the replenishment of these newly formed T lymphocytes.

Methods: VL/HIV patients, grouped into non-relapsing (NR- = 6) and relapsing (R- = 12) were evaluated from the active phase up to 12 months post-treatment (mpt). HIV-infected patients (non-VL) and healthy subjects (HS) were included. The TCRVβ repertoire was evaluated ex vivo by flow cytometry, whereas the plasmatic cytokine levels were assessed by Luminex assay. To evaluate the thymic output, DNA was extracted from PBMCs for TCR rearrangement excision circles (TREC) quantification by qPCR.

Results: VL/HIV cases presented an altered mobilization profile (expansions or retractions) of the TCRVβ families when compared to HS independent of the follow-up phase (p < 0.05). TCRVβ repertoire on CD4⁺ T-cells was more homogeneous in the NR-VL/HIV cases, but heterogeneous on CD8⁺ T-cells, since different Vβ-families were mobilized. NR-VL/HIV had the inflammatory pattern reduced after 6 mpt. Importantly, VL/HIV patients showed number of TREC copies lower than controls during all follow-up. An increase of recent thymic emigrants was observed in NR-VL/HIV individuals at 10 mpt compared to R- patients (p < 0.01), who maintained lower TREC contents than the HIV controls.

Conclusions: VL/HIV patients that maintain the thymic function, thus generating new T-cells, seem able to replenish the T lymphocyte compartment with effector cells, then enabling parasite control.

Leishmania infantum Virulence Factor A2 Protein: Linear B-Cell Epitope Mapping and Identification of Three Main Linear B-Cell Epitopes in Vaccinated and Naturally Infected Dogs

In Brazil, canine visceral leishmaniasis (CVL) is caused by Leishmania infantum, presenting a broad spectrum of clinical manifestations. Dogs are the main parasite reservoir in urban areas and canine cases precede human infection. Currently, A2 protein based Leish-Tec® vaccine is the only vaccine commercially available against CVL in Brazil. Considering that the main screening and confirmatory tests of canine infection are serological, it is possible that the antibody response elicited after vaccination interfere with diagnosis, leading to the inability to distinguish between vaccinated and infected animals. In order to identify the specific B-cell response induced after vaccination, A2 protein sequence was screened for main linear B-cell epitopes using in silico prediction (Bepipred) and immunological confirmation by ELISA. Three amino acid sequences were described as potential B-cell epitopes (SV11-SAEPHKAAVDV, PP16-PQSVGPLSVGPQSVGP, and VQ34-VGPLSVGPQSVGPLSVGPLSVGPQAVGPLSVGPQ). Specific IgG ELISAs were performed in sera of 12 immunized dogs living in non-endemic areas, followed for up to 1 year after immunization. The results were compared with those obtained in a group of 10 symptomatic and 10 asymptomatic CVL dogs. All predicted epitopes were confirmed as linear B-cell epitopes broadly recognized by sera from studied dogs. Total IgG ELISAs demonstrated distinct patterns of response between peptides in the immunized and CVL groups. VQ34 peptide was recognized by the majority of sera from vaccinated and symptomatic dogs, and increases after vaccination. PP16 induced low levels of specific IgG that increased 1 year after immunization. Interestingly, a low frequency of reactivity was found against SV11 in naturally infected dogs (symptomatic and asymptomatic), while 83.3% of vaccinated dogs presented positive responses 1 year after immunization. The two animals in the vaccinated group that did not respond to SV11 1 year after immunization presented positive serology both 30 days and 6 months after immunization. In summary, we identified three main linear B-cell epitopes in A2 based vaccine. Moreover, the humoral response against SV11 presented marked differences between infected and Leish-Tec vaccinated dogs, and should be further investigated, in large trials, to confirm its potential as a serological marker able to distinguish between infected and vaccinated dogs.

Lutzomyia longipalpis Saliva Drives Interleukin-17-Induced Neutrophil Recruitment Favoring Leishmania infantum Infection

During bloodfeeding, the presence of sand fly saliva in the hemorrhagic pool where Leishmania is also inoculated modulates the development of host immune mechanisms creating a favorable environment for disease progression. To date, information obtained through experimental models suggests that sand fly saliva induces cellular recruitment and modulates production of eicosanoids. However, the effect of sand fly saliva in the different steps of the inflammatory response triggered by Leishmania remains undefined. Here we further investigate if interaction of Lutzomyia longipalpis salivary gland sonicate (SGS) with different host cells present during the initial inflammatory events regulate Leishmania infantum infectivity. Initially, we observed that incubation of human peripheral blood mononuclear cells (PBMC) with Lu. longipalpis SGS in the presence of L. infantum significantly increased IL-10 but did not alter expression of IFN-γ and TNF-α by CD4⁺ T cells induced by the parasite alone. Interestingly, incubation of PBMC with Lu. longipalpis SGS alone or in the presence of L. infantum resulted in increased IL-17 production. The presence of IL-17 is related to neutrophil recruitment and plays an important role at the site of infection. Here, we also observed increased migration of neutrophil using an in vitro chemotactic assay following incubation with supernatants from PBMC stimulated with L. infantum and Lu. longipalpis SGS. Neutrophil migration was abrogated following neutralization of IL-17 with specific antibodies. Moreover, culture of human neutrophils with L. infantum in the presence of Lu. longipalpis SGS promoted neutrophil apoptosis resulting in increased parasite viability. Neutrophils operate as the first line of defense in the early stages of infection and later interact with different cells, such as macrophages. The crosstalk between neutrophils and macrophages is critical to determine the type of specific immune response that will develop. Here, we observed that co-culture of human macrophages with autologous neutrophils previously infected in the presence of Lu. longipalpis SGS resulted in a higher infection rate, accompanied by increased production of TGF-β and PGE₂. Our results provide new insight into the contribution of Lu. longipalpis SGS to L. infantum-induced regulation of important inflammatory events, creating a favorable environment for parasite survival inside different host cells.

CD3+CD4negCD8neg (double negative) T lymphocytes and NKT cells as the main cytotoxic-related-CD107a+ cells in lesions of cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis

Background

Cutaneous leishmaniasis (CL) is caused by Leishmania (Viannia) braziliensis, which infects dermal macrophages and dendritic cells, causing an intense immune-mediated-tissue inflammation and a skin ulcer with elevated borders that can heal spontaneously or after antimonial therapy. The resolution of lesions depends on an adaptive immune response, and cytotoxic cells seem to have a fundamental role in this process. The aim of this study is to better understand the role of cytotoxicity mediated mechanisms that occur during the immune response in the CL lesion milieu, considering distinct cytotoxic-related CD107a⁺ cells, such as CD8⁺, CD4⁺, CD4^neg CD8^neg (double-negative, DN) and CD4⁺CD8⁺ (double-positive, DP) T lymphocytes, as well as NK and NKT cells.

Methods

Lesion derived cells were assessed for T cell subpopulations and NK cells, as well as CD107a expression by flow cytometry. In addition, cytometric bead array (CBA) was used to quantify cytokines and granzyme B concentrations in supernatants from macerated lesions.

Results

Flow cytometry analyses revealed that NKT cells are the major CD107a-expressing cell population committed to cytotoxicity in CL lesion, although we also observed high frequencies of CD4⁺ and DN T cells expressing CD107a. Analysing the pool of CD107a⁺-cell populations, we found a higher distribution of DN T cells (44%), followed by approximately 25% of NKT cells. Interestingly, NK and CD8⁺ T cells represented only 3 and 4% of the total-CD107a⁺-cell pool, respectively.

Conclusions

The cytotoxicity activity that occurs in the lesion milieu of CL patients seems to be dominated by DN T and NKT cells. These findings suggest the need for a reevaluation of the role of classical-cytotoxic NK and CD8⁺ T cells in the pathogenesis of CL, implicating an important role for other T cell subpopulations.

Differences in immune responses against Leishmania induced by infection and by immunization with killed parasite antigen: implications for vaccine discovery

The leishmaniases are a group of diseases caused by different species of the protozoan genus Leishmania and transmitted by sand fly vectors. They are a major public health problem in almost all continents. There is no effective control of leishmaniasis and its geographical distribution is expanding in many countries. Great effort has been made by many scientists to develop a vaccine against leishmaniasis, but, so far, there is still no effective vaccine against the disease. The only way to generate protective immunity against leishmaniasis in humans is leishmanization, consisting of the inoculation of live virulent Leishmania as a means to acquire long-lasting immunity against subsequent infections. At present, all that we know about human immune responses to Leishmania induced by immunization with killed parasite antigens came from studies with first generation candidate vaccines (killed promastigote extracts). In the few occasions that the T cell-mediated immune responses to Leishmania induced by infection and immunization with killed parasite antigens were compared, important differences were found both in humans and in animals. This review discusses these differences and their relevance to the development of a vaccine against leishmaniasis, the major problems involved in this task, the recent prospects for the selection of candidate antigens and the use of attenuated Leishmania as live vaccines.

Using Proteomics to Understand How Leishmania Parasites Survive inside the Host and Establish Infection

Leishmania is a protozoan parasite that causes a wide range of different clinical manifestations in mammalian hosts. It is a major public health risk on different continents and represents one of the most important neglected diseases. Due to the high toxicity of the drugs currently used, and in the light of increasing drug resistance, there is a critical need to develop new drugs and vaccines to control Leishmania infection. Over the past few years, proteomics has become an important tool to understand the underlying biology of Leishmania parasites and host interaction. The large-scale study of proteins, both in parasites and within the host in response to infection, can accelerate the discovery of new therapeutic targets. By studying the proteomes of host cells and tissues infected with Leishmania, as well as changes in protein profiles among promastigotes and amastigotes, scientists hope to better understand the biology involved in the parasite survival and the host-parasite interaction. This review demonstrates the feasibility of proteomics as an approach to identify new proteins involved in Leishmania differentiation and intracellular survival.

T-cell receptor Vβ repertoire of CD8+ T-lymphocyte subpopulations in cutaneous leishmaniasis patients from the state of Rio de Janeiro, Brazil

In human cutaneous leishmaniasis (CL), the immune response is mainly mediated by T-cells. The role of CD8⁺ T-lymphocytes, which are related to healing or deleterious functions, in affecting clinical outcome is controversial. The aim of this study was to evaluate T-cell receptor diversity in late-differentiated effector (LDE) and memory CD8⁺ T-cell subsets in order to create a profile of specific clones engaged in deleterious or protective CL immune responses. Healthy subjects, patients with active disease (PAD) and clinically cured patients were enrolled in the study. Total CD8⁺ T-lymphocytes showed a disturbance in the expression of the Vβ2, Vβ9, Vβ13.2, Vβ18 and Vβ23 families. The analyses of CD8⁺T-lymphocyte subsets showed high frequencies of LDE CD8⁺T-lymphocytes expressing Vβ12 and Vβ22 in PAD, as well as effector-memory CD8⁺ T-cells expressing Vβ22. We also observed low frequencies of effector and central-memory CD8⁺ T-cells expressing Vβ2 in PAD, which correlated with a greater lesion size. Particular Vβ expansions point to CD8⁺ T-cell clones that are selected during CL immune responses, suggesting that CD8⁺ T-lymphocytes expressing Vβ12 or Vβ22 are involved in a LDE response and that Vβ2 contractions in memory CD8⁺T-cells are associated with larger lesions.

Proteome profiling of human cutaneous leishmaniasis lesion

In this study, we used proteomics and biological network analysis to evaluate the potential biological processes and components present in the identified proteins of biopsies from cutaneous leishmaniasis (CL) patients infected by Leishmania braziliensis in comparison with normal skin. We identified 59 proteins differently expressed in samples from infected and normal skin. Biological network analysis employing identified proteins showed the presence of networks that may be involved in the cell death mediated by cytotoxic T lymphocytes. After immunohistochemical analyses, the expression of caspase-9, caspase-3, and granzyme B was validated in the tissue and positively correlated with the lesion size in CL patients. In conclusion, this work identified differentially expressed proteins in the inflammatory site of CL, revealed enhanced expression of caspase-9, and highlighted mechanisms associated with the progression of tissue damage observed in lesions.

Limited T cell receptor beta variable repertoire responses to ESAT-6 and CFP-10 in subjects infected with Mycobacterium tuberculosis

Mycobacterium tuberculosis (MTB)-specific antigens, ESAT-6 or CFP-10 play a key role in diagnosis and control MTB infection. T cell receptor (TCR) reflects the status and function of T cells. However, the features of the TCR beta variable (TCRBV) repertoire used against ESAT-6 and CFP-10 from MTB subjects have not been well described. The molecular profiles of TCRBV complementarity-determining region 3 (CDR3) in PBMCs with or without ESAT-6 or CFP-10 stimulation were assayed using a gene melting spectral pattern (GMSP) assay developed in our previous study. The average number of skewed TCRBV family in PBMCs stimulated with ESAT-6 or CFP-10 was significantly higher than that in unstimulated PBMCs. TCRBV3, BV5.1, BV12, BV13.1, BV13.2, BV20 and BV24 were used more frequently than other TCRBV members in PBMCs from MTB subjects, and TCRBV3, BV5.1 in stimulated PBMCs have a preference in the usage of variable (V) and joining (J) segments and CDR3. The results indicate that the T cell immune response in MTB subjects involves a few of specific T cells. The preferred usage of certain V and J segments and CDR3s of TCRBV3 or BV5.1 may be related to ESAT-6 or CFP-10 respectively, which would help clinical differential diagnosis and treatment of MTB-infected subjects.

The immunobiology of Leishmania braziliensis infection

Leishmaniases are a group of diseases caused by protozoa of the genus Leishmania that affect millions of people worldwide. These diseases are caused by distinct Leishmania species, of which L. braziliensis, a New World representative of the Leishmania genus, has been the least studied. Although leishmaniasis caused by L. braziliensis induces a range of clinical manifestations ranging from mild localized lesions to severe mucosal involvement, few studies have focused on elucidating the immune mechanisms behind this pathology. In this review, we focus on the immunobiology of L. braziliensis infection, emphasizing the innate and adaptive immune responses and taking into consideration both studies performed in endemic areas and experimental models of infection. Additionally, we address recent findings regarding the role of sand fly saliva in disease immunopathogenesis and vaccine development.

Quantitative analysis of T cell receptor diversity in clinical samples of human peripheral blood

The analysis of T cell receptor diversity provides a clinically relevant and sensitive marker of repertoire loss, gain, or skewing. Spectratyping is a broadly utilized technique to measure global TCR diversity by the analysis of the lengths of CDR3 fragments in each Vβ family. However the common use of large numbers of T cells to obtain a global view of TCR Vβ CDR3 diversity has restricted spectratyping analyses when limited T-cell numbers are available in clinical setting, such as following transplant regimens. We here demonstrate that one hundred thousand T cells are sufficient to obtain a robust, highly reproducible measure of the global TCR Vβ repertoire diversity among twenty Vβ families in human peripheral blood. We also show that use of lower cell number results not in a dwindling of observed diversity but rather in non-reproducible patterns in replicate spectratypes. Finally, we report here a simple to use but sensitive method to quantify repertoire divergence in patient samples by comparison to a standard repertoire profile we generated from fifteen normal donors. We provide examples using this method to statistically evaluate the changes in the global TCR Vβ repertoire diversity that may take place during T subset immune reconstitution after hematopoietic stem cell transplantation or after immune modulating therapies.

Role of TLR4 and TCR or BCR against baicalin-induced responses in T and B cells

Baicalin (BA), a flavonoid compound isolated from Scutellaria baicalensis, has been shown to possess a number of pharmacological effects including antiviral, anti-inflammatory, antioxidant and immune regulation. Here, we examined its effects on human T and B cells proliferation by MTT assay and found that BA stimulated T and B cells proliferation, independently and cooperatively with Con-A (T cells) or LPS (B cells). Then, we analyzed the effects of BA treatment on the mRNA expression of Toll-like receptors (TLRs), IL-2, IFN-γ and IL-12 in T and B cells by real-time RT-PCR and attempted to observe whether blocking TLR4 had influence on mRNA expression. We found that BA treatment significantly up-regulated TLR3, 7, 8 and 9 mRNA expressions in T and B cells, IL-2 and IFN-γ in T cells and IL-12 in B cells. The increased mRNA expressions were suppressed after blocking TLR4. We further analyzed the effects of BA treatment on TCR vβ and CD79 mRNA expression levels in T and B cells and explored whether blocking TCR (αβ) or BCR mIgM F(ab')(2) had an influence on mRNA expression. We found that BA treatment significantly improved TCR vβ and CD79 mRNA expression in T and B cells, respectively, and the improvements were all inhibited after blocking TCR (αβ) or BCR mIgM F(ab')(2). Our results suggested that BA participates in innate and adaptive immune regulation by up-regulating the mRNA expression of TLRs (3, 7, 8 and 9), IL-2, IFN-γ and IL-12 in T and B cells, which is mediated by TLR4, and by improving the mRNA expression of TCR vβ and CD79, which is mediated by TCR (αβ) and BCR mIgM, respectively. Therefore, TLR4, TCR (αβ) and BCR mIgM are all the immune receptors for BA on T and B cells.

CD4(+) T cells defined by their Vβ T cell receptor expression are associated with immunoregulatory profiles and lesion size in human leishmaniasis

Leishmaniasis is caused by infection with the protozoan parasite, Leishmania, that parasitizes human cells, and the cellular immune response is essential for controlling infection. In order to measure the host T cell response to Leishmania infection, we have measured the expansion, activation state and functional potential of specific T cells as identified by their T cell receptor Vβ region expression. In a group of cutaneous leishmaniasis (CL) patients, we evaluated these characteristics in nine different T cell subpopulations as identified by their Vβ region expression, before and after specific Leishmania antigen stimulation. Our results show: (1) an increase in CD4(+) T cells expressing Vβ 5·2 and Vβ 24 in CL compared to controls; (2) a Leishmania antigen-induced increase in CD4(+) T cells expressing Vβ 5·2, 11, 12 and 17; (3) a profile of previous activation of CD4(+) Vβ 5·2-, 11- and 24-positive T cells, with higher expression of CD45RO, HLA-DR, interferon-γ, tumour necrosis factor-α and interleukin-10 compared to other Vβ-expressing subpopulations; (4) a positive correlation between higher frequencies of CD4(+) Vβ5·2(+) T cells and larger lesions; and (5) biased homing of CD4(+) T cells expressing Vβ 5·2 to the lesion site. Given that CL disease involves a level of pathology (ulcerated lesions) and is often followed by long-lived protection and cure, the identification of specific subpopulations active in this form of disease could allow for the discovery of immunodominant Leishmania antigens important for triggering efficient host responses against the parasite, or identify cell populations most involved in pathology.

Mycobacterium tuberculosis culture filtrate protein 10-specific effector/memory CD4⁺ and CD8⁺ T cells in tubercular pleural fluid, with biased usage of T cell receptor Vβ chains

T cell-mediated immunity is critical for the control of Mycobacterium tuberculosis infection. Identifying the precise immune mechanisms that lead to control of initial M. tuberculosis infection and preventing reactivation of latent infection are crucial for combating tuberculosis. However, a detailed understanding of the role of T cells in the immune response to infection has been hindered. In addition, there are few flow cytometry studies characterizing the Vβ repertoires of T cell receptors (TCRs) at local sites of M. tuberculosis infection in adult tuberculosis. In this study, we used culture filtrate protein 10 (CFP-10) from M. tuberculosis to characterize T cells at local sites of infection. We simultaneously analyzed the correlation of the production of cytokines with TCR Vβ repertoires in CFP-10-specific CD4(+) and CD8(+) T cell subsets. For the first time, we demonstrate that CFP-10-specific CD4(+) or CD8(+) T cells from tubercular pleural fluid can produce high levels of gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) and upregulate the expression of CD107a/b on the cell surface. The CFP-10-specific cells were effector/memory cells with a CD45RO(+) CD62L(-) CCR7(-) CD27(-) expression profile. In addition, we found CFP-10-specific CD4(+) and CD8(+) T cells in tubercular pleural fluid, with biased usage of TCR Vβ9, Vβ12, or Vβ7.2. Our findings of CFP-10-specific CD4(+) and CD8(+) T cells in tubercular pleural fluid are critical for understanding the mechanisms of the local cellular immune response and developing more effective therapeutic interventions in cases of M. tuberculosis infection.

Interleukin-10 and immunity against prokaryotic and eukaryotic intracellular pathogens

The generation of an effective immune response against an infection while also limiting tissue damage requires a delicate balance between pro- and anti-inflammatory responses. Interleukin-10 (IL-10) has potent immunosuppressive effects and is essential for regulation of immune responses. However, the immunosuppressive properties of IL-10 can also be exploited by pathogens to facilitate their own survival. In this minireview, we discuss the role of IL-10 in modulating intracellular bacterial, fungal, and parasitic infections. Using information from several different infection models, we bring together and highlight some common pathways for IL-10 regulation and function that cannot be fully appreciated by studies of a single pathogen.

Efficient characterization of the TCR repertoire in lymph nodes by flow cytometry

Analysis of the T-cell receptor (TCR) repertoire by flow cytometry proved to be relevant for investigating T-cell diversity and detecting reactive cells in blood samples. We used this approach to characterize non-malignant T-lymphocytes in lymph nodes and give insights into their origin. The TCR repertoire of CD4+ and CD8+ T-cells from 81 lymph nodes was analyzed with a four-color flow cytometer using a wide panel of 25 anti-Vbeta monoclonal antibodies. Flow cytometry proved to be a useful and informative technique. We demonstrated a diversified TCR-Vbeta repertoire, and only low level expansions, in 53% of the samples. They involved nearly all Vbeta families, were more frequent in the CD8+ subset of older patients, but were not related to pathology. No evidence could be demonstrated in favor of stimulation by common antigens. Interestingly, the TCR-Vbeta repertoire proved to be very similar in lymph nodes and blood samples. Our results argue that in the cases studied, lymph node enlargement is mainly due to an increased homing of circulating T-cells. They also provide reference values for expression of 25 TCR-Vbeta in lymph nodes, which could serve as a basis for further applications in diagnosis of T-cell lymphoproliferative disorders.

Contrasting human cytokine responses to promastigote whole-cell extract and the Leishmania analogue receptor for activated C kinase antigen of L. amazonensis in natural infection versus immunization

It is known that the same antigen can induce different immune responses, depending upon the way that it is presented to the immune system. The objective of this study was to compare cytokine responses of peripheral blood mononuclear cells (PBMC) from cutaneous leishmaniasis patients and subjects immunized with a first-generation candidate vaccine composed of killed Leishmania amazonensis promastigotes to a whole-cell promastigote antigen extract (La) and to the recombinant protein LACK (Leishmania analogue receptor for activated C kinase), both from L. amazonensis. Thirty-two patients, 35 vaccinees and 13 healthy subjects without exposure to Leishmania, were studied. Cytokine production was assessed by enzyme-linked immunosorbent assay and enzyme-linked immunospot assay. The interferon (IFN)-gamma levels stimulated by La were significantly higher and the levels of interleukin (IL)-10 significantly lower than those stimulated by LACK in the patient group, while LACK induced a significantly higher IFN-gamma production and a significantly lower IL-10 production compared with those induced by La in the vaccinated group. LACK also induced a significantly higher frequency of IFN-gamma-producing cells than did La in the vaccinated group. The contrast in the cytokine responses stimulated by LACK and La in PBMC cultures from vaccinated subjects versus patients indicates that the human immune response to crude and defined Leishmania antigens as a consequence of immunization differs from that induced by natural infection.