Transmission intensity and human immune responses to lymphatic filariasis

Our understanding of how the host immune response influences the risk of de veloping disease has changed dramatically over the past decade. Previously, the spectrum of disease associated with lymphatic filariasis was largely a ttributed to the nature of the host immune response. Now, we appreciate tha t the duration and intensity of infection and possibly the direct influence of parasite-derived molecules also determine the risk of disease. Individu als chronically infected with lymphatic filariasis generally have an impair ed lymphocyte proliferation response to filarial antigens and favour Th2-ty pe cytokine responses. This ability to down-modulate the host immune respon se may help protect the host from disease. Defects in antigen-presenting ce ll (APC) function appear to participate in this acquired immune hyporespons iveness, although the mechanisms as to how this occurs are poorly understoo d. Here, we present evidence that repeated exposure to infective stage larv ae and their secreted products may stimulate basophils and mast cells to re lated products that may impair APC function.