Post-partum antibody-dependent cell-mediated immunity in the rat following perinatal exposure to iodine-131

A study was recently completed which indicated the first generation of adult rats that had been exposed perinatally to iodine-131 possessed peripheral blood lymphoid-cells capable of expressing cytotoxicity towards cultured small bowel adenocarcinoma target cells, i.e., active antitumor cell-mediated immunity (CMI). The results gathered during the current investigation suggest that such animals similarly express anti-tumor antibody-dependent cell-mediated immunity (ADCC). The animal model employed consisted of Fisher F344 inbred rats exposed to iodine-131 (sodium) during their 16th to 18th day of gestation, and at an interval of two months post-partum when the offsprings had matured into adults, they and their mothers were evaluated for the presence of serum components capable of expressing ADCC activities toward X-ray induced small bowel adenocarcinoma target cells. Significant ADCC activities were found to be expressed by the offspring while no analogous immunological responses could be detected in the serum of the mothers. This lack of maternal ADCC activity suggests the existence of a biological block developing during pregnancy resulting in the mother being immunological nonresponsive to carcinogenic insults. One serum component present in the offspring identified as being responsible for initiating ADCC was an immunoglobulin of the IgG class as based upon its physical characteristics: solubility, molecular weight, and reactivity with anti-immunoglobulins, pepsin, and protein A. The interpretation of these findings is that perinatal exposure to radioiodine results in the development of cells having foreign-like properties in the offspring which are recognized by the animal's immune system, thus resulting in detectable antitumor CMI and ADCC immune responses.