Background: The red cells of almost all human beings bear P antigen. Type P1 cells (around 75% of the population) contain P1 antigen in addition to P, and type P2 cells (around 25% of the population) contain only P. The red cells of only a few individuals are devoid of P: these cells may be of either Pk-positive (P1k and P2k[Pk]) or p type (the latter lack all the above-described antigens of the P system). Differentiation between them is of clinical importance, but there is a shortage of specific reagents. This article offers reliable means for differentiation.
Study design and methods: Agglutination of washed, papain-treated red cells of all the P types by PA-1 and soybean lectins and adsorption of the lectins onto the red cells were examined.
Results: PA-1 strongly agglutinated papain-treated red cells. Examination of its interactions with red cells having different P system antigens revealed that Pk (both P1k and P2k) red cells of O, A, and B blood types were agglutinated significantly faster than p red cells. The agglutination intensities of Pk red cells of types O and A (most people) was considerably stronger than those of p red cells. P1 and P2 type red cell agglutination was intermediate (P1>P2). Adsorption tests with all the red cells, exhibited the same order of PA-1 affinities for the P system blood types: Pk>P1,>P2>p. The soybean lectin exhibited opposite behavior (p>P2>P1>Pl).
Conclusion: The galactose-binding lectins PA-1 and soybean may facilitate the determination of Pk and p red cells.