IMMUNOSUPPRESSION BY A NEUTRAL THIOL PROTEASE FROM PARASITIC HELMINTHLARVAE IN MICE

The composition and immunological suppression of a novel proteinaceous material, a neutral thiol pretense (NTP), isolated from the metacerca ria of the helminth Paragonimus westermani are reported. From cDNA clo ning and sequencing, the protease was found to be composed of 215 amin o acid residues and closely resembled the known cysteine proteases. Tr eatment of adult mice with the enzyme suppressed the delayed footpad r eaction and haemagglutinin antibody production, and reduced expression of the major histocompatibility complex and interleukin 2 receptor on lymphocytes, and induced suppressor cells in the spleen. In addition, stable and long-term skin graft survival was achieved by concomitant administration of the enzyme at a low dose.