The haemagglutinins in boar seminal plasma are absorbed by ejaculated washed motile ram, bull and rabbit spermatozoa. Washed epididymal spermatozoa also absorb the haemagglutinin, but less avidly.
Considerable motility of the heterologous spermatozoa is still present after 15 min contact with boar seminal plasma. Mixed cell agglutination of bull spermatozoa and red cells gives a reticulate agglutination visible microscopically, and tail to tail agglutination occurs.
The haemagglutinins are absorbed at least as well by washed pig red cell ghosts as by the intact washed erythrocytes. The absorptive power of the ghosts is not destroyed by boiling them in n-NaOH or n-HCl for one hour.
It is presumed that a negatively charged `receptor' group on the surface of the red cell is responsible for the absorption. The receptor does not appear to be connected with erythrocyte sialic acid removable by receptor-destroying enzyme, trypsin or by 0·1 n-HCl.