The traditional concept that effector T helper (Th) responses are mediated by Th1/Th2 cell subtypes has been broadened by the recent demonstration of two new effector T helper cells, the IL-17 producing cells (Th17) and the follicular helper T cells (Tfh). These new subsets have many features in common, such as the ability to produce IL-21 and to express the IL-23 receptor (IL23R), the inducible co-stimulatory molecule ICOS, and the transcription factor c-Maf, all of them essential for expansion and establishment of the final pool of both subsets. Tfh cells differ from Th17 by their ability to home to B cell areas in secondary lymphoid tissue through interactions mediated by the chemokine receptor CXCR5 and its ligand CXCL13. These CXCR5+ CD4+ T cells are considered an effector T cell type specialized in B cell help, with a transcriptional profile distinct from Th1 and Th2 cells. The role of Tfh cells and its primary product, IL-21, on B-cell activation and differentiation is essential for humoral immunity against infectious agents. However, when deregulated, Tfh cells could represent an important mechanism contributing to exacerbated humoral response and autoantibody production in autoimmune diseases. This review highlights the importance of Tfh cells by focusing on their biology and differentiation processes in the context of normal immune response to infectious microorganisms and their role in the pathogenesis of autoimmune diseases.

A new subtype of CD4 + T lymphocytes characterized by the production of interleukin 17, i.e., TH17 cells, has been recently described. This novel T cell subset is distinct from type 1 and type 2 T helper cells. The major feature of this subpopulation is to generate significant amounts of pro-inflammatory cytokines, therefore appearing to be critically involved in protection against infection caused by extracellular microorganisms, and in the pathogenesis of autoimmune diseases and allergy. The dynamic balance among subsets of T cells is important for the modulation of several steps of the immune response. Disturbances in this balance may cause a shift from normal immunologic physiology to the development of immune-mediated disorders. In autoimmune diseases, the fine balance between the proportion and degree of activation of the various T lymphocyte subsets can contribute to persistent undesirable inflammatory responses and tissue replacement by fibrosis. This review highlights the importance of TH17 cells in this process by providing an update on the biology of these cells and focusing on their biology and differentiation processes in the context of immune-mediated chronic inflammatory diseases.

Resumo: a obesidade comumente é associada com outras doenças como: hipertensão arterial, diabetes mellitus tipo II, cardiovasculares e inflamação crônica. Estudos demonstram o tecido adiposo (TA) como um órgão endócrino capaz de influenciar a homeostase energética e hemodinâmica, além de ter papel importante na resposta inflamatória. O termo adipocina é utilizado para nomear peptídeos bioativos sintetizados e secretados por adipócitos. O interesse em estudar essas proteínas teve início com a descoberta da leptina e suas diversas funções, hoje já sabemos que o TA secreta outros hormônios, proteínas de fase aguda, quimiocinas, fatores hemostáticos e hemodinâmicos e fatores de crescimento. Este trabalho teve por objetivo estudar os principais grupos de adipocinas visando uma maior compreensão de seus mecanismos de ação, das finalidades e influências no desenvolvimento da obesidade e estado de inflamação crônica. Foi observado que essas adipocinas em desequilíbrio promovem impacto em diversas funções corporais, alterando a ingesta alimentar, sensibilidade à insulina, resposta imune, angiogênese, pressão arterial, metabolismo lipídico e balanço energético. Dessa maneira se faz necessária uma compreensão dos efeitos do tratamento como atividade física, nutrição, aspecto psicológico e clínica sobre o controle hormonal e de citocinas, a fim de se desenvolver terapias mais eficazes, diminuindo as complicações da obesidade. Palavras-chave: Adipocinas. Leptina. Adiponectina. Resistina. Obesidade.Abstract: the obesity is commonly associated with other diseases such as hypertension, diabetes mellitus type II, cardiovascular and chronic inflammation. Studies revealed adipose tissue (AT) as an endocrine organ capable of influencing the energy and hemodynamic homeostasis, and play an important role in the inflammatory response. The adipokine term is used to name bioactive peptides synthesized and secreted by adipocytes. The interest in studying these proteins began with the discovery of leptin and its various functions, today we know that the TA secret other hormones, acute phase proteins, chemokines, hemostatic and hemodynamic factors and growth factors. This study aims to investigate the major adipokines groups seeking a greater understanding of their mechanisms of action, its purposes and influences the development of obesity and chronic state of inflammation. It was observed that these imbalance adipokines have a impact on several body functions, altering dietary intake, insulin sensitivity, immune response, angiogenesis, blood pressure, lipid metabolism and energy. Thus, a understanding of the effects of treatment such as physical activity, nutrition, psychological and clinical aspects on hormonal and cytokine control is necessary in order to develop more effective therapies, reducing the complications of obesity.