Immune response to Candida albicans Resposta imune a Candida albicans

Candida albicans causes infections of the skin, oral cavity and esophagus, gastrointestinal tract, vagina and vascular system. Most infections occur in immunocompromised hosts or debilitated patients. More than 90% of HIV positive patients suffer from mucosal candidiasis at least once in the course of this disease. The overall severity and chronicity of oral candidiasis in patients with AIDS are mainly attributed to the HIV-induced immune deficiency in the affected individuals, namely, the loss of T-helper cells and reduction in the number of CD4+ T lymphocytes. In mucosal colonization and systemic infections of mice by this fungus, Th1 cells mediate phagocyte-dependent protection, whose most important cytokines are IL-2, IFN- , TNF-á and IL-12. In contrast, production of inhibitory cytokines such as IL-4 and IL- 10 by Th2 cells are associated with disactivation of phagocytes and disease progression. Possibly, the growth of filamentous forms is better adapted to evade the cells of the immune system, whereas the yeast form may be the mode of proliferation in infected tissues. By the discriminative production of IL- 12 or IL-4 in response to the yeast or filamentous forms respectively, dendritic cells acquire the capacity of inducing the differentiation of CD4+ cells towards the Th1 or Th2 phenotypes. Candida albicans causa infec es na pele, cavidade oral e es fago, trato gastrointestinal, vagina e sistema vascular de humanos. As infec es ocorrem em hospedeiros imunocomprometidos ou pacientes debilitados. Acima de 90% dos pacientes HIV+ sofrem de candidíase de mucosas ao menos uma vez no decorrer da doen a. A severidade e cronicidade da candidíase oral em pacientes com AIDS s o atribuídas, principalmente, à imunodeficiência induzida pelo HIV nos indivíduos afetados, a saber, perda de fun es de célula T auxiliar e redu o do número de linfócitos T CD4. Na coloniza o de mucosas e infec es sistêmicas de camundongos por este fungo, células Th1 medeiam a prote o dependente de fagócitos, cujas citocinas mais importantes s o IL-2, IFN- e IL-12, TNF-á. Ao contrario, produ o de citocinas inibidoras tais como, IL-4 e IL-10 por células Th2 est o associadas à desativa o de fagócitos e à progress o da doen a. Possivelmente, o crescimento de formas filamentosas está melhor adaptado para evadir das células do sistema imune, enquanto a forma de levedura pode ser o modo de prolifera o em tecidos infectados. Pela produ o discriminativa de IL-12 em resposta a levedura e de IL-4 a hifa, as células dendríticas adquirem a capacidade para induzir a diferencia o de c