The "A" antigen of pigeon erythrocytes detectable by Phaseolus Zunatus lectin was given the nomenclature "Aze1" to designate it as the agglutinogen of Columba Zivia which is apparently identical to the A2 of man.
This antigen appeared at day 10 in ouo and increased linearly to day 17. (The average incubation time of pigeon embryos was 17.4 days.) At the time of hatching 2% of the expected, parental titer was reached. After another linear increase from one to seven days post-hatching, the titer of the squab bloods exceeded the parental titer, arriving at a maximum of 160% at one month post-hatching. The level then slowly decreased to 110% of the average parental titer at three months post-hatching and remained stable thereafter.
The ratio of human cells to pigeon cells involved in mixed agglutination was used to show that high-titer bloods (older eggs) contain an abundance of cells with multiple active sites and a few cells lacking active sites, whereas low-titer bloods (younger eggs) contain mostly inactive cells or cells with proportionately fewer sites.
Hemagglutination inhibition tests performed on plasma from eggs and neonatal squabs failed to detect the presence of a soluble Aze' antigen. These results, together with the in ovo development of the antigen and the detection of the antigen in embryonic bone marrow cells, indicate that the agglutinogen may develop in the early stem cells and then be carried over onto the maturing red cells.