AbstractAn attempt was made to identify the filarial specific antigens that are capable of inducing immune response in human filariasis. Lymphocytes were taken from three clinically defined groups living in an endemic area in Madras, namely microfilaraemic (MF) subjects with microfilariae in their blood smear without any clinical symptoms, chronic pathology (CP) individuals with lymphangitis or lymphadenitis in combination with a history of recurrent filarial fevers or lymphoedema, and endemic normals (EN) subjects without microfilariae nor any clinical symptoms of pathology. Lymphocytes from the three groups responded with no significant difference (P= 0.21) in their proliferative index to PPD and PHA, although lymphocytes from MF individuals showed significantly (P< 0.001) less proliferative index toBrugia malayiantigen (BMA) than the CP and EN subjects. This antigen specific cellular unresponsiveness seen in MF patients was not reversed by the addition of recombinant IL-lα, IL-1β, and IFN-γ, but the addition of sera from EN individuals seemed to restore this unresponsiveness (P< 0.001). The peripheral blood mononuclear cells from MF patients secreted more IL-1 in response to BMA induction than the same from CP and EN individuals. A 58 kDa recombinant protein isolated from aWuchereria bancroftigenomic library (58 kDa) had mounted a higher proliferative response to lymphocytes from all three groups compared to BMA (P< 0.001) indicating the possible use of recombinant filarial protein to mount immunological responses in filarial patients.