A Study of a Complex Precipitating System Containing Two Cross-Reacting Egg Albumins as Antigens

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Abstract
Summary: Using simple diffusion in gel tubes, either hen egg albumin (HEA) or duck egg albumin (DEA) reacting alone with an anti-HEA rabbit serum gave the expected straight line relation when, with time constant, the penetrations h were plotted against the logarithm of the concentration g of the reacting antigen. The relation followed the previously described equation: h = γlogg/g0 where g0 is a constant, proportional to the concentration of the antibody reacting with HEA or DEA. The slope γ was the same for HEA and DEA. When the two egg albumins were mixed in varying proportions, two precipitation zones were usually observed. The penetration of the zone of HEA was slightly increased by the presence of DEA, while the penetration of the zone of DEA was greatly increased by the presence of HEA. An equation has been derived which predicts approximately the penetration hD of the zone of DEA from the concentrations gH and gD of HEA and DEA in the mixture: where g0H and g0D represent the g0 values for HEA and DEA in the 1st equation and γ is the slope derived from the 1st equation. After partial absorption of the serum with DEA, the slopes were no longer identical for the two egg albumins reacting alone, so that no equation of the above type could be applied to the reaction of the mixtures, but the general features of the curves remained the same as above. The maximum amounts of antibody nitrogen precipitable by HEA and DEA from nonabsorbed serum and serum absorbed with varying amounts of DEA were determined. It was noted that a) the difference between the two maximum values did not vary much when the quantity of the heterologous antigen DEA used for absorption was within a certain range, and b) the amount of antibody precipitable by HEA after absorption by DEA did not reach its lowest value for a previous absorption by DEA at the equivalence ratio. If the previous absorption was carried out with an excess of DEA, the antibody precipitable by HEA was still further decreased. Two possible explanations for the latter observation have been discussed.