Delayed anti-kappa response in kappa-deficient mice after neonatal, oral immunization with kappa-containing IgG

Antibody responses to kappa (κ)-light (L) chain are absent in normal (Cκ+/+) animals because of tolerance due to the abundance of κ-L chains expressed on more than 95% of all B cells and serum Ig. eterozygous κ-sufficient (Cκ+/−) females are bred with homozygous κ-deficient (Cκ−/−) males, half of their offspring will become κ-deficient but have received κ-L chain containing maternal Ig, mainly IgG and IgA, through placental and intestinal transmission. The κ-containing maternal Ig persists for more than 2 months in the circulation of the offspring. Starting from weeks 15 to 20 of age, a spontaneous antibody response towards the maternal κ-L chains can be recorded. The time of onset, as well as the magnitude of the responses differ among individuals of the same litter. Invariably, once a response has been initiated, it transits into an IgG-type of response, which upon injection with κ-containing protein shows the features of a secondary type of immune response.