Changes in antibody and complement production in Xenopus laevis during postmetamorphic development revealed in a primary in vivo or in vitro antibody response.

Xenopus laevis (G-line) mounts a primary plaque forming cell (PFC) response either in vivo or in vitro following challenge with foreign erythrocytes. Methods are described for generating and assaying the response, which specify criteria such as antigen dose, antigen choice, response kinetics, and complement source. The results suggest that at the peak of the primary response (approximately day 6), animals of different ages produce predominantly different 'classes' of antibody which display markedly different complement-fixing characteristics. Antibodies produced by larvae and 4-month-old postmetamorphic animals appear here to be unable to fix either guinea pig complement (GPC') or adult Xenopus complement, but can readily fix complement from 6-month-old Xenopus. The proportion of spleen PFC's producing antibody capable of fixing GPC' progressively increases from about six months to 18 months of age. Possible explanations for such ontogenetic changes are discussed.