Immune responses and chronic lymphedema in experimental filariasis

Chronic lymphedema is a clinically important manifestation of lymphatic filariasis but the factors which govern the development and progression of lymphedema remain unclear. Because immune responses are major determinants of disease expression in filariasis, we compared immune responses in ferrets reinfected with B. malayi in which disease expression varied from virtually no overt disease to severe chronic lymphedema of the infected limbs. No immune correlates specific for development of chronic lymphedema were identified by antigen recognition profiles (Western-blots), magnitude of the antibody (IgG) responses (ELISA) or blastogenic responses of lymphocytes to filarial extracts. Prausnitz-Kustner (PK) tests for filarial specific IgE indicated that the initial period of a severe lymphedema, which became chronic, often was associated with relatively high IgE titers. The results suggest that a high level of immediate hypersensitivity to filarial antigens is a significant factor in initiating persistent lymphedema on reinfections of partially resistant hosts. Histologic study of persistent edema of up to 2 years duration demonstrated dermal changes consistent with chronic lymphedema, but not the dermal proliferation characteristic of elephantiasis.