Abstract
Treatment with nontoxic monophosphoryl lipid A increased the magnitude of the immunoglobulin M (IgM) antibody response to type III pneumococcal polysaccharide in young (2- to 4-week-old) mice. This was accompanied by the appearance of significant numbers of IgG1- and IgG3- secreting antibody-forming cells in 4-week-old mice. These findings indicate that monophosphoryl lipid A can be used as an adjuvant to improve the immunogenicity of poorly immunogenic antigens in young, immunologically immature animals.