Antigenic Composition, Not the Degree of Polymerization, Determines the Requirement for Thymus-Derived Cells in Immune Responses to Salmonella Flagellar Proteins

Abstract

Abstract Two flagellar proteins, prepared from either SW1338 or SL167 strains of Salmonella, have a differential requirement for thymus-derived (T) cells in producing a primary IgM response in mice. By using two methods for T cell depletion, the SW1338 flagellar protein, in both monomeric and polymeric forms, induced an IgM response that was essentially the same as that found in normal mice. In contrast, the SL167-derived antigen failed to initiate the appearance of antibody-forming cells in T cell-deprived mice. These findings add a further dimension to the consideration of mechanisms which underlie the collaboration between T and B cells, namely the role of epitope composition. In view of a failure to demonstrate differences between monomeric and polymeric forms of the antigen, it is argued that the arrangement of epitopes is not an essential requirement for T cell-independent IgM responses in vivo.