Plasmacytoid dendritic cells (pDCs) recognise viral single-stranded RNA (ssRNA) or CpG DNA via Toll-like receptor (TLR)-7 and TLR9, and produce interferon (IFN)-α. Activated pDCs upregulate human leukocyte antigen (HLA)-DR and CD86 expression levels. Ingestion of bovine lactoferrin (LF) activates pDCs, but little is known about its effects. In this study, the effects of LF and its pepsin hydrolysate (LFH) on the production of IFN-α from peripheral blood mononuclear cells (PBMCs) and pDCs were examined. PBMCs were prepared from peripheral blood of healthy adults and incubated with LF, LFH, or lactoferricin (LFcin) in the absence or presence of ssRNA derived from human immunodeficiency virus. The concentration of IFN-α in the supernatant and the expression levels of IFN-α, HLA-DR, and CD86 in pDCs were quantified by enzyme-linked immunosorbent assay and flow cytometry. In the absence of ssRNA, the concentration of IFN-α was negligible and LF had no effect on it. In the presence of ssRNA, IFN-α was detected at a certain level, and LF and LFH significantly increased its concentration. The increase caused by LFH and LFcin were comparable. In addition, LF significantly upregulated the expression levels of IFN-α, HLA-DR, and CD86 in pDCs. LF and its digestive peptides induced IFN-α production and activated pDCs in the presence of ssRNA, suggesting that LF modulates the immune system by promoting pDC activation upon viral recognition.

Objectives: We investigated the effects of bovine lactoferrin (LF) on the maintenance of the respiratory and systemic physical conditions. Methods: A randomized, double-blind, placebo-controlled trial was conducted. Healthy adults at Kyushu University of Health and Welfare ingested a placebo or bovine LF (200 mg/day) for 12 weeks. The primary endpoints were the total respiratory and systemic symptom scores. The secondary endpoint was the activity of plasmacytoid dendritic cells (pDCs) in peripheral blood. Results: A total of 157 subjects were randomized (placebo, n = 79; LF, n = 78), of whom, 12 dropped out. The remaining 145 participants were included in the full analysis set (placebo group, n = 77; LF group, n = 68). The total scores for respiratory and systemic symptoms during the intervention were significantly lower in the LF group than in the placebo group. The expression of CD86 and HLA-DR on pDCs was significantly higher in the LF group than in the placebo group at week 12. Adverse events were comparable between the groups, and no adverse drug reactions were observed. Conclusions: These results suggest that orally ingested LF supports the normal immune system via maintaining pDC activity, and maintains respiratory and systemic physical conditions in healthy adults.

Plasmacytoid dendritic cells (pDCs) express Toll-like receptor 7 (TLR7) in the endosomes, recognize viral single-stranded RNA (ssRNA), and produce significant amounts of interferon (IFN)-α. Bovine lactoferrin (LF) enhances the response of IFN regulatory factors followed by the activation of IFN-sensitive response elements located in the promoter regions of the IFN-α gene and IFN-stimulated genes in the TLR7 reporter THP-1 cells in the presence of R-848, a TLR7 agonist. In ex vivo experiments using human peripheral blood mononuclear cells, LF enhances IFN-α levels in the supernatant in the presence of R-848. Additionally, it increases the expression of IFN-α, human leukocyte antigen (HLA)-DR, and CD86 in pDCs; HLA-DR and CD86 in myeloid dendritic cells; CD69 in CD56 dim natural killer and T killer cells; and IFN-γ in T helper type 1 and B cells in the presence of R-848. The inhibition of phagocytosis or neutralization of nucleolin, a receptor of LF, suppresses LF incorporation into pDCs. These results suggest that pDCs incorporate LF through phagocytosis or nucleolin-mediated endocytosis, and LF enhances TLR7 response in the endosome and subsequent IFN signaling pathway and activates innate and adaptive immune cells. We anticipate that LF modulates antiviral immunity against environmental ssRNA viruses and contributes to homeostasis.

To evaluate the effects of a single ingestion of bovine lactoferrin (bLF) on oral and throat conditions under a low-humidity environment. A randomized, double-blind, 2-sequence, 2-treatment, and 2-period placebo-controlled crossover trial was conducted. Healthy adult subjects orally ingested bLF dissolved in water, or placebo water, followed by exposure to low humidity (20 °C, 20% relative humidity (RH)) for 2 h. The primary endpoint was subjective oral and throat discomfort assessed by a visual analog scale (VAS), which positively correlated with the discomfort. Secondary endpoints were unstimulated whole salivary flow rate (UWSFR) and salivary immunoglobulin A (IgA) secretion rate. Overall, 40 subjects were randomly assigned to two sequences (20 each) and 34 were analyzed. The VAS values for oral and throat discomfort in the bLF treatment were significantly lower than in the placebo treatment, whereas UWSFR and IgA secretion rates were comparable between the two treatments. Adverse drug reactions were not observed. Subjective oral and throat discomfort associated with low humidity is suppressed by a single ingestion of bLF. Our findings demonstrate the novel use of bLF in a clinical situation that leverages its unique characteristics.

Background Sphingomyelin (Sph) is a bioactive phospholipid, and its ingestion is suggested to improve skin conditions. Dairy products are accessible dietary sources of Sph. We investigated the effects of dairy-derived Sph on skin conditions. Methods A randomized, double-blind, placebo-controlled trial was conducted. The participants were healthy adult women aged 30-59 years recruited in Japan, who ingested a tablet containing dairy-derived Sph (23.6 mg/day) or a placebo tablet for 12 weeks. The primary endpoints were skin hydration and transepidermal water loss (TEWL). The secondary endpoint was the subjective perception of skin hydration. Results Overall, 94 participants were enrolled and randomly assigned to two groups (placebo, n = 48; Sph, n = 46). At the end of the intervention, 84 participants remained, and 83 (placebo, n = 44; Sph, n = 39) were analyzed. The increase in skin hydration levels on the upper arm in the Sph group was higher than that in the placebo group. TEWL and subjective perception of skin hydration showed no significant differences between the two groups. The incidence of adverse events was comparable between groups, and no adverse drug reactions were found. Conclusion Intake of dairy-derived Sph is safe and improves skin hydration. Sph-rich dairy products can be used to maintain skin health.