T cell receptor signaling pathway is overexpressed in CD4 + T cells from HAM/TSP individuals

ABSTRACT Human T-lymphotropic virus type 1 (HTLV-1) is a human retrovirus related to the chronic neuroinflammatory disease HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). CD4+ T cells activation appears to play a key role on HTLV-1 infection. Here we investigated the expression of genes associated to T cell activation CD3e molecule, epsilon (CD3?), lymphocyte-specific protein tyrosine kinase (LCK), vav 1 guanine nucleotide exchange factor (VAV1), and zeta-chain (TCR) associated protein kinase 70 kDa (ZAP70) on T lymphocytes of HTLV-1-infected individuals and compared to healthy uninfected individuals (CT). We observed that CD3?, LCK, ZAP70, and VAV1 gene expression were increased in CD4+ T cells from HAM/TSP group compared to HTLV-1 asymptomatic patients (HAC). Moreover, ZAP70 and VAV1 were also upregulated in HAM/TSP compared to CT group. We detected a positive correlation among all these genes. We also observed that CD3?, LCK, and VAV1 genes had a positive correlation with the proviral load (PVL) and Tax expression. These results suggest that PVL and Tax protein could drive CD3?, LCK, and VAV1 gene expression in CD4+ T cells, and these genes function on a synchronized way on the CD4+ T cell activation. The elucidation of the mechanisms underlying T cell receptor signaling pathway is of considerable interest and might lead to new insights into the mechanism of HAM/TSP.

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.

Perfil de ativação dos linfócitos T de pacientes com mielopatia associada ao vírus linfotrópico das células T humanas do tipo 1 (HTLV-1) / paraparesia tropical espástica (HAM/TSP) possível, provável e definido / Activation profile of T lymphocytes of patients with myelopathy associated with human T-lymphotropic virus type 1 cells (HTLV-1) tropical spastic paraparesis (HAM / TSP) possible, probable and definite

O vírus linfotrópico das células T humanas do tipo 1 (HTLV-1) é o agente etiológico da mielopatia associada ao HTLV / paraparesia espástica tropical (HAM / TSP ), que ocorre em menos de 5 % dos indivíduos infectados. A resposta imune controla parcialmente a infecção, porém pode estar ligada a patogênese da doença. O objetivo deste estudo foi caracterizar fenotipicamente as subpopulações de linfócitos T, em pacientes assintomáticos e com diagnóstico de HAM/TSP. Foram avaliados 103 pacientes acompanhados no Centro de HTLV da Escola Bahiana de Medicina e Saúde Pública (EBMSP) e 19 controles não infectados. Os pacientes foram categorizados de acordo com o grau de certeza do diagnóstico de HAM/TSP: possível (Ps), provável (Pb) e definido (D), além de pacientes assintomáticos (ASS). O perfil fenotípico (CD25, CD45RA, CD45RO, HLA-DR, CD25, CCR-7, CD62L)...

The human T-cell lymphotropic vírus type 1(HTLV-1) is the etiological agent of HTLV- associated myelopathy/ Tropical spastic paraparesis(HAM/TSP), wich occurs in less then 5% of the infected individuals. The immune response partially controls the infection, but may be linked to the pathogenesis of disease. The aim of this study was to characterize phenotipically T lymphocyte subpopulations in asymptomatic and in patients diagnosed with HAM/TSP. We evaluated 103 patients treated at the center for HTLV of Bahia School of Medicine and Public Health (EBMSP) and 19 uninfected controls. Patients were categorized as asymptomatic and according to the degree of certainty of the diagnosis of HAM/TSP: Possible(Ps), Probable(Pb) and Definite(D). The phenotypic profile (CD25, CD45RA, CD45RO, HLA-DR, CCR-7, CD62L)...

Investigation of T cell receptors in the peripheral blood of patients with active pulmonary tuberculosis.

T cells have the capability of recognizing target cells through their T cell receptors (TCRs). Thus, the percentages of CD3+/gamma-delta (gammadelta) TCR+ and CD3+/alpha-beta (alphabeta) TCR+ T lymphocytes were investigated in active and inactive pulmonary tuberculosis (PT) patients and in healthy individuals. CD3+ and CD3+/alphabeta TCR+ cell percentages were significantly lower in all PT patients than in healthy subjects. Percentages of CD3+/gammadelta and CD3+/alphabeta TCR+ were not statistically different between active and inactive PT patients. It was concluded that alphabeta TCR+ T cells might have a protective role in tuberculosis infection.

Las células T reguladoras y su influencia en la sobrevida del trasplante renal / Regulatory T cells and their influence in kidney allograft survival

La respuesta inmune desencadenada frente a un trasplante alogénico conduce usualmente a una respuesta efectora que resulta en el rechazo del aloinjerto; sin embargo, algunos individuos mantienen un trasplante funcionante a largo plazo sin signos de rechazo (tolerancia operacional), aun en ausencia de inmunosupresión. Se ha sugerido que los mismos mecanismos son responsables para la tolerancia hacia antígenos propios y aloantígenos. Uno de estos mecanismos es la regulación inmune y se han identificado varias subpoblaciones de células con propiedades reguladoras. Entre ellas, la población celular mejor caracterizada corresponde a las células T reguladoras (Tregs). Aunque las Tregs en ratones son CD4+CD25+, en humanos el fenotipo de las Treg está restringida a las células T CD4 con alta expresión de CD25 (CD25high) y del factor de transcripción Foxp3. El análisis fenotípico y funcional de las células T reguladoras o supresoras circulantes en pacientes trasplantados tal vez sea útil para la detección de pacientes tolerantes operacionales. Además, una futura manipulación in vitro de estas células con fines terapéuticos podría conducir a lograr la inducción de tolerancia in vivo en el trasplante clínico. Aquí, revisamos la evidencia experimental y clínica del papel de las células reguladoras en la biología del trasplante.

The immune response elicited by an allogenic transplant usually leads to an effector response resulting in allograft rejection; however, some individuals maintain a long-term functioning transplant without signs of rejection (operational tolerance) even in the absence of immunosuppression. It has been suggested that the same mechanisms are responsible for tolerance to self-antigens and alloantigens. One of such mechanisms is immune regulation and several cell subsets with regulatory properties have been identified. Among them, the best characterized cell populations are the regulatory T cells (Treg). Although Treg in mice are CD4+CD25+, in humans the Treg phenotype is restricted to CD4 T cells with high expression of CD25 (CD25high) and Foxp3. Phenotypic and functional analysis of circulating regulatory or suppressor T cells in transplant patients may be useful for detection of operationally tolerant patients. Moreover, future in vitro manipulation of these cells with therapeutic purposes could lead to accomplish induction of in vivo tolerance in clinical transplantation. Herein, we review the experimental and clinical evidence for the role of regulatory cells in transplant biology.

CD99 activates T cells via a costimulatory function that promotes raft association of TCR complex and tyrosine phosphorylation of TCR zeta

We investigated the co-stimulatory role of a cell-surface protein, CD99. Co-ligation of CD99 and suboptimal CD3 induced T-cell activation to a level comparable to that obtained with optimal CD3 or CD3+CD28. We also noted concomitant enhancement of the earliest T-cell receptor (TCR) signaling events. In addition, co-ligation of CD99 and CD3 led to translocation of TCR complexes into the lipid raft, without concomitant migration of CD99 to the raft, and consequent enhancement of TCR zeta-mediated signal 1. These data demonstrate the unique properties of CD99 co-stimulation that distinguish this molecule from CD28 and other raft-resident co-stimulatory factors.

Susceptible hosts: a resort for parasites right in the eye of the immune response

Trypanosomatid protozoan parasites express an aggressive strategy of parasitism by infecting host macrophages and inducing extensive T-lymphocyte activation. One goal of such strategy is to drive the immune response of genetically susceptible hosts to a state of unresponsiveness regarding parasite killing. Unresponsiveness is achieved through different mechanisms, depending on the parasite species. In this brief review, recent findings on the molecular and cellular bases of the parasites' exploitation of host immune responses are discussed.

Receptores de células T y complejo CD3 / T cell receptors and CD3 complex

Tanto las células T como las células B contactan con antígenos a través de moléculas especializadas presentes en su superficie. En las células T, se han descrito dos tipos de estructuras para interactuar con los antígenos, se trata de los TCR alfa-beta y TCR gamma-delta. El primero, es el que se distribuye más ampliamente en las células T periféricas y timocitos portadores de un receptor definido. Se trata de moléculas heterodiméricas compuestas de dos cadenas polipeptídicas unidas entre sí. En una célula se expresan miles de copias de un receptor cuyas especificidades epitópicas son idénticas, sin embargo, la presencia de un tipo de receptor excluye la del otro. Las células T pueden ser, independiente del receptor desplegado, CD8- CD4+ o CD8+ CD4-, cumpliendo, por lo tanto, funciones ayudadoras o citotóxicas, respectivamente. Ambos receptores para efectuar sus actividades requieren de la expresión de un complejo proteico llamado CD3, compuesto por 5 proteínas denominadas alfa, delta, épsilon, dseta y eta cuya misión, en presencia de interacción con el antígeno, es transducir señales a través de la membrana celular del linfocito. El receptor de la célula T reconoce al antígeno asociado a proteínas de la membrana plasmática, conocidas como moléculas de histocompatibilidad clase I o II, dependiendo si se trata de células no inmunológicamente comprometidas, o bien, células presentadoras de antígeno o linfocitos, respectivamente. La estrategia para generar diversidad en los TCR es similar a la utilizada para las inmunoglobulinas. Los genes que codifican para los TCR se generan por medio de recombinaciones somáticas de segmentos génicos durante la etapa germinal de las células T

Superantigenos: una particular interaccion entre microorganismos y el sistema inmune / Superantigens: a particular interaction between microorganisms and the immune system

El descubrimiento de los superatígenos (SAgs) aportó nuevos conceptos en el estudio de las interacciones entre los microorganismos y el sistema inmune. Se trata de moléculas que, asociadas a las de Clase II del Complejo Mayor de Histocompatibilidad (CMH), se unen al dominio variable de la cadena Beta Vbeta) del receptor de antígenos Ags) de los linfocitos T alphaBeta (TCRalphaBeta) que les confiere la especialidad de familia. Así, los SAgs son capaces de activar a un alto número de linfocitos T y de células portadoras de las moléculas de Classe II del CMH, generando una masiva liberación de linfoquinas y mediadores inflamatorios que ha sido relaciona con sus efectos tóxicos. Los SAgs endógenos están codificados por los provirus de tumores murinos (Mtv) que se hallan integrados al genoma de los ratones. Los exógenos son producidos por bacterias y virus, siendo los mejor caracterizados los relacionados con las intoxicaciones alimentarias. Aun no se han hallado datos concluyentes en cuanto a la existencia de SAgs de parásitos y se requieren estudos más detallados para establecer su presencia y posible efecto en las infecciones parasitarias.