Implications of infectious diseases and the adrenal hypothesis for the etiology of childhood acute lymphoblastic leukemia

Acute leukemia is the most frequent cancer in children. Recently, a new hypothesis was proposed for the pathogenesis of childhood acute lymphoblastic leukemia (ALL). The so-called "adrenal hypothesis" emphasized the role of endogenous cortisol in the etiology of B-cell precursor ALL. The incidence peak of ALL in children between 3 to 5 years of age has been well documented and is consistent with this view. The adrenal hypothesis proposes that the risk of childhood B-cell precursor ALL is reduced when early childhood infections induce qualitative and quantitative changes in the hypothalamus-pituitary-adrenal axis. It suggests that the increased plasma cortisol levels would be sufficient to eliminate all clonal leukemic cells originating during fetal life. Because Brazil is a continental and tropical country, the exposure to infections is diversified with endemic viral and regionally non-viral infections, with some characteristics that support the recent adrenal hypothesis. Here we discuss this new hypothesis in terms of data from epidemiological studies and the possible implications of the diversity of infections occurring in Brazilian children.

Neuroimunomodulação: sobre o diálogo entre os sistemas nervoso e imune / Neuroimmunomodulation: the cross-talk between nervous and immune systems

OBJETIVO: Trabalhos de pesquisa provenientes do campo da neuroimunomodulação vêm tornando explícitas as intrincadas relações existentes entre o sistema nervoso central e o sistema imune. Uma revisão bibliográfica foi realizada com o objetivo de descrever as bases de estudo da neuroimunomodulação. MODELOS EXPERIMENTAIS: Sabe-se, hoje, que estados emocionais como ansiedade e depressão são capazes de modificar a atividade do sistema imune como também o fazem o estresse e fármacos com ação no sistema nervoso central. COMPORTAMENTO DOENTIO: Os comportamentos apresentados por um organismo doente devem ser encarados como decorrência de estratégias homeostáticas de cada indivíduo. POSSÍVEIS MECANISMOS DE SINALIZAÇÃO DO SISTEMA IMUNE PARA O SISTEMA NERVOSO CENTRAL: Grande destaque tem sido atribuído para a participação do eixo hipotálamo-pituitária-adrenal, do sistema nervoso autônomo simpático e das citocinas nas sinalizações entre o sistema nervoso central e o sistema imune. CONCLUSÃO: O presente artigo pretende mostrar a relevância dos fenômenos de neuroimunomodulação; ele faz uma análise crítica das influências do sistema nervoso central sobre o sistema imune e vice-versa.

OBJECTIVE: Several papers arriving from the neuroimmunomodulation field are showing the relevant relationships between the nervous and the immune systems. A review of studies was carried out to describe the bases of the studies on neuroimmunomodulation. EXPERIMENTAL MODELS: It is clear nowadays that emotional states such as anxiety and depression change immune system activity, an affect also observed after both stress and use of nervous system acting drugs. SICK BEHAVIOR: The behavior displayed by sick organisms might be thought as being a consequence of homeostatic strategies. POSSIBLE MECHANISM OF THE ACTION BY MEANS OF IMMUNE SYSTEM TO NERVOUS SYSTEM: A very big emphasis is being given to Hipothalamus-pituitary-adrenal axis, simpathetic nervous system and cytokines participation on nervous system and immune system relationships. CONCLUSION: The present revision intend to show some essential studies in the neuroimmunomodulation field; it makes a critical analysis of the mutual relationships between nervous system and immune system.

Estres, depresión e inmunología / Stress, depression and immunology

Estrés es un concepto científico que se refiere a la respuesta inespecífica del organismo frente a cualquier demanda, en la cual la capacidad de adaptación individual constituye el factor más importante. Los sistemas nervioso, endocrino e inmune están en estrecha interrelación y hoy en día la célula inmune puede considerarse un órgano sensorial ya que es capaz de responder tanto a estímulos físicos como psíquicos. Se revisan las características del sistema inmune, la red neuroinmunoendocrina y los mecanismos de neuro-inmuno-modulación. El estudio de la inmunidad celular en la depresión se ha abordado, in vitro, a través del recuento de células, de la proliferación de linfocitos mediante mitógenos y de la actividad de las células natural killer. En pacientes, in vivo, se ha determinado la respuesta cutánea de hipersensibilidad retardada. Los resultados en general han sido contradictorios ya que existen reparos metodológicos y diversos factores; edad, gravedad del cuadro depresivo, hospitalización, trastornos del sueño, baja de peso, que dificultan las conclusiones definitivas. Las alteraciones en la función noradrenégica o en el eje hipotálamo-hipófisis-adrenal pudieran explicar algunos casos de deterioro de la inmunidad en la depresión