Specific cellular immune unresponsiveness in human filariasis

Abstract

In an effort to identify factors important in the pathogenesis of filarial disease, studies of the cellular and humoral immune responses to the parasitic nematode Wuchereria bancrofti were carried out on thirty-nine individuals in a region of the Pacific where filariasis is endemic.

Blood lymphocytes from twenty-six patients with chronic filariasis (especially that associated with persistent microfilaraemia) gave only minimal responses to filarial antigens when challenged in vitro in a lymphocyte transformation assay. In contrast, brisk responses to these same antigens were elicited in cultures of cells from a control population of thirteen exposed but not infected individuals living in the same area, the greatest responses being found in uninfected children less than 10 years old. The poor cellular responsiveness of infected individuals was filaria antigen-specific, as reactivity to tuberculin (PPD) and streptococcal (SK—SD) antigens was normal and equal in all groups. Furthermore, the immunologic deficit was limited to cell-mediated immune responses and appeared unchanged 2 weeks after treatment of the patients with the anti-filarial drug diethylcarbamazine.

We interpret our findings as evidence for a state of antigen-specific cellular unresponsiveness in patients with this chronic parasitic infection and speculate that this immunologic deficit may be of fundamental importance in the pathogenesis of filarial disease.