The Rho(D) Specificity of a Polysaccharide Isolated from a Species of Pseudomonas

A polysaccharide from an unidentified species of Pseudomonas (PsP) has been shown to possess antigenic specificity similar to the Rho(D) antigen of human red cells. The following findings revealed this specificity: a) PsP inhibited anti-D agglutinins; b) anti-PsP rabbit sera contained both saline agglutinins and incomplete antibodies specific only for cells containing D antigen; c) D-positive cells absorbed specific agglutinins from anti-PsP sera; d) anti-D serum blocked agglutination of D cells by anti-PsP serum. Agglutination of D cells by anti-PsP rabbit serum was inhibited by N-acetylneuraminic acid (NANA) containing substances different from those previously shown to inhibit D cell agglutination by specific Rh antiserum. It was concluded that the antigenic similarity is not due to NANA but to some structure or linkage resembling it.