Maternal kappa-containing IgG induces a late anti-Κ response in adult, Κ-deficient offspring

Kappa (kappa)-light (L) chain-deficient (C kappa-/-) mice readily mount a T cell-dependent antibody response after immunization with kappa -containing proteins. Such antibody responses are absent in normal (C kappa+/+) animals because of tolerance due to the abundance of kappa -L chains expressed on more than 95% of all B cells and serum immunogiobulins. When heterozygous ic-sufficient (C kappa+/-) females are bred with homozygous; kappa -deficient (C kappa-/-) males, half of their offspring will become kappa -deficient but have received kappa -L chain containing maternal Ig, mainly IgG and IgA, through placental and intestinal transmission. The kappa -containing maternal Ig persists for more than 2 months in the circulation of the offspring. Starting from week 15-20 of age, a spontaneous antibody response towards the maternal kappa -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 IgGtype of response, which upon injection with kappa -containing protein shows the features of a secondary type of immune response.