The purpose of this project is to define the humoral and cellular immune responses that relate to immunopathology, protective immunity and immunodiagnosis of patients with filariasis. Qualitative analysis of filaria-specific IgE and IgG subclass antibodies indicates different antigen recognition patterns among groups of patients with different clinical manifestations of filariasis and a special "linkage" or parallelism between the recognition patterns for IgE and IgG4 antibodies. This latter may account for the finding of "blocking antibodies" that control immediate hypersensitivity responses in patients with this and other chronic helmith infections. Immunoregulatory studies have extended the description of immune suppression in microfilameric patients to include antibody production as well as T-cell induced blastogenesis. The lymphokines IL-2 and Gamma-interferon are not produced by the cells of such patients if stimulated in vitro by filarial antigen but are induced by the presence of other non-filarial antigens or mitogens. Assessment of local pulmonary pathology in patients with tropical eosinophilia (TPE) by bronchoalveolar lavage (BAL) has indicated extreme elevations of specific IgE, IgG and IgM antibodies, increased cell numbers and abnormal production of oxidants by alveolar cells. Longitudinal BAL studies show that such alveolitis persists in patients despite standard treatment regimens and, therefore, suggest that more vigorous therapy for TPE must be developed.