72 страниц. 2014 год. LAP Lambert Academic Publishing The human Immune responses are directed to eliminate infectious pathogens from the host body. Th1 CD4 cells are involved in the destruction and removal of intracellular pathogens while Th2 CD4 cells are responsible for ejection of extracellular parasites. Since Th1 and Th2 immune cells are cross regulatory molecules, intestinal (extracellular) parasites, initiate the type two immune responses in which more CD4 Th2 cells are produced and the host immune response become activated chronically. In Th2 directed chronic immune activation, Th1 immune cells become down regulated by a strong production of Th2 immune cells and the generation of specific cytotoxic T lymphocytes for HIV will be impaired. This situation provides chance for HIV to replicate at high rate and leads more CD4 cells to be infected and resulting immune suppression. In immune suppressive state, opportunistic infections become aggravate and give rise in to a complex disease; AIDS.