Lactoferrin, a major defense protein of innate immunity, is a novel maturation factor for human dendritic cells.

Lactoferrin (LF) is an important protein component of the innate immune system that is broadly distributed within the body fluids. LF is endowed with multiple biological activities. Talactoferrin (TLF), a recombinant human LF, is in clinical development as an anticancer agent and is entering Phase III clinical trials. Here, we show that TLF induces the maturation of human dendritic cells (DCs) derived from monocytes. TLF, at physiologically relevant concentrations (100 microg/ml) up-regulates the expression of human leukocyte antigen (HLA) class II, CD83, CD80, and CD86 costimulatory molecule and CXCR4 and CCR7 chemokine receptors, acting primarily through the p38 MAPK signaling pathway. DCs matured by TLF displayed an enhanced release of IL-8 and CXCL10, as well as a significantly reduced production of IL-6, IL-10, and CCL20. They also display a reduced ability to take up antigen and increased capacity to trigger proliferation and release IFN-gamma in the presence of allogeneic human T cells. TLF-matured DCs are able to prime naive T cells to respond to KLH antigen and display a significantly increased capacity to present Flu-MA(58-66) peptide to HLA-A2-matched T cells. These data suggest that a key immunomodulatory function that may be mediated by TLF is to link the innate with adaptive immunity through DC maturation.