Table 2.

Immunologic Mechanisms for the Nonspecific Protective Effects of Vaccines^a

Epigenetic modification of monocytes

Cross-reaction between B and T cells, conferring protection from other pathogens

Favored differentiation of Th1 cells, increasing IFN-γ and propagated recruitment of innate immune cells

Production of mucosal IgA/IgG

Competition with invasive pathogens for host factors

Early activation of CD4 and CD8 T cells via PRR, including TLR

Anti-inflammatory properties

Early protection against tissue damage

Increase in granulopoiesis

Abbreviations: IFN, interferon; Ig, immunoglobulin; TLR, Toll-like receptor.

^aSummary of proposed mechanisms discussed in this paper.