Western immunoblot from SDS-PAGE carried out simultaneously with that of the Figure 3 and with the same primary and secondary antibodies. Paths 1 and 10: prestained MW standards high and low range, respectively. Paths 2–5: four different samples from ceE 53 hours. Paths 5–9: ceE 72 hours and 5–7–9 days, respectively. Five sF-TrAg with circa 250, 200, 90, 52 and 34 kDa are present in 53-hour-old chick embryo inasmuch as all sF-TrAg present in the different age samples was detected by the antibodies induced by the chick embryo 53 h-old extract. The six stars point out the five bands.