Heterogeneity of the haemagglutinin responses to Salmonella minnesota R-antigens in rabbits

Summary: Homologous and heterologous haemagglutinin responses in rabbits to heat-killed R-mutants of Salmonella minnesota (chemotypes ranging from Ra to Re) were measured throughout the course of immunization. In each case the strongest response was directed against the homologous R-antigen, but in most cases cross-reactions with antigens of heterologous R-chemotypes were detected. Absorption studies with erythrocytes coated with R-lipopolysaccharides indicated that haemagglutinin reactions with homologous and heterologous R-antigens in R-antisera were due to several different populations of antibodies. In general, these populations consisted of: (i) antibodies strictly specific for the homologous antigen; (ii) antibodies reacting with the homologous antigen, but also able to react in varying degrees with heterologous R-lipopolysacharides of more complete chemo-types; (iii) antibodies directed against internal portions of the R-oligosaccharide; and (iv) antibodies strictly specific for a less complete form of the R-oligosaccharide molecule. Characteristic responses were obtained for each of the R-mutants with respect to the presence or absence of any one of the above-mentioned antibody populations in antisera at a given period after immunization.