Mechanisms by which maternal antibodies influence infant vaccine responses: review of hypotheses and definition of main determinants.

Several mechanisms have been suggested as mediating the inhibitory influence of maternal antibodies (MatAb) on infant responses. This inhibition is B cell determinant-specific, depends on the ratio between MatAb titers at the time of immunization and the dose of vaccine antigen, and leaves infant T cell responses largely unaffected. Neutralization of vaccine replication or FcgammaRIIB-mediated inhibitory signalling to infant B cells would not account for these characteristics. In contrast, determinant-specific masking of B cell epitopes and APC uptake of MatAb:vaccine antigen immune complexes, followed by antigen processing and presentation, explain the pattern of pre-clinical and clinical responses to infant vaccines. This allows the definition of the main determinants of the influence of MatAb on infant immunity.