A conjugate vaccine is created by covalently attaching a poor (polysaccharide organism) antigen to a carrier protein (preferably from the same microorganism), thereby conferring the immunological attributes of the carrier on the attached antigen. An unconjugated polysaccharide antigen will not be loaded onto the MHC complex, which can only bind peptides, and thus will not be presented to a T cell for activation of the presenting B cell. In the case of a conjugate vaccine, the carrier peptide linked to the polysaccharide target antigen is able to be presented on the MHC molecule. The T cell that recognizes the carrier peptide will activate that B cell, causing it to produce antibodies to the polysaccharide antigen that it had originally bound. This technique for the creation of an effective immunogen is most often applied to bacterial polysaccharides for the prevention of invasive bacterial disease.