The spontaneous regression of neuroblastoma (NB), one of the most common malignant tumors in childhood, is found to occur in 1% to 2% of patients with NB, especially in young infants. An unexpectedly favorable response to therapy is also noticed in infants suggesting the potential presence of an immune mechanism. Monoclonal C1300-S and C1300A-4 cell lines were established from polyclonal C1300 cells in our laboratory. Adult female A/J mice that had rejected 1 x 10(3) NB cells (C1300S-3) or 1 x 10(5)-10(6) NB cells (C1300A-4) were used as immunized mothers. The immunized mothers with C1300A-4 or C1300S-3 were found to have specific antibodies to C1300S-3 cells by 51Cr release assay of complement dependent cytotoxicity. Newborn mice, 24 hours after birth from immunized or nonimmunized mothers, were inoculated with 1 x 10(3) C1300S-3 NB cells. The same antibody that was assayed in the immunized mothers was detected in this offspring by the antibody-dependent cell cytotoxicity (ADCC). The tumor incidence in the offspring of the immunized mothers was found to be less than that of the offspring of the nonimmunized mothers. This study suggests that the lower tumor incidence in the offspring of immunized mothers compared with offspring of nonimmunized mothers may be attributed to their ADCC activity. Furthermore, the antibody that has the ADCC activity was proven to be immunoglobulin G by a serum absorption test using IgG absorbant. This study offers insight into the relationship between transported mother-infant immunoglobulins and on its potential control of NB.