Studies on lectin affinities of chicken alpha-fetoprotein during ontogeny

Alpha-fetoprotein in the sera of chicken embryos (ch-AFP) of the 7th, 10th, 13th, 16th, and 19th day of incubation and of one-day-old chickens were examined in crossed-immunoaffino-electrophoresis (CIAE) using different lectins [concanavalin A (Con A), lentil, wheat germ lectin, and soybean lectin] as ligands. Differences in lectin affinities, suggesting different degrees or forms of glycosylation of ch-AFP during ontogeny, were demonstrated by this method. Sera of chicken embryos of the same stages were also subjected to Con A affinity chromatography and the elution patterns were evaluated qualitatively in CIAE and quantitatively in rocket immunoelectrophoresis. These experiments revealed a major Con A-nonreactive and a minor Con A-reactive fraction at the 7th day of incubation. In contrast, a minor Con A nonreactive fraction and a major Con A-reactive fraction were observed at later stages of embryonic life. Extracts from embryos of the 8th and 15th day of incubation did not exhibit heterogeneity when subjected to CIAE. The biological significance of these observations, as well as the biological role of AFP in general, remains to be elucidated. Examination of ch-AFP glycosylation patterns might be included into the spectrum of analyses when certain early teratological processes in the chicken embryo are to be monitored. In addition, these molecular changes have to be considered when in vitro or in vivo experiments on the biological, especially immunological, role of ch-AFP are envisaged.