Supplementation with oligomeric procyanidins [OPCs] from apples and acai - and likely other sources such as grape seed extract and pycnogenol - activates the immune system. OPCs can help the innate part of the immune system respond more quickly to pathogens, reducing the risk of disease.

Apple OPCs research
In 2014, immunologists at Montana State University published a series of experiments with Apple Poly in the Journal of Leukocyte Biology. Apple Poly is an apple extract with a high concentration of oligomeric procyanidins (OPCs). The manufacturer of Apple Poly did not sponsor the research.

Some of the experiments were in vitro. The researchers also conducted experiments with laboratory animals and humans.

In vitro study
The researchers exposed human immune cells to interferon-alpha. When human cells come into contact with viruses or other pathogens, increased interferon-alpha production is one of the very first immunological responses.

The ensuing responses are driven by activation of the signaling protein and transcription factor STAT1 [pSTAT1]. The presence of OPCs from apples enhanced this response. [APP] OPCs from a different source - a standardized supplement containing acai extract - also did so. [AS]

Click on the figure below for a larger version.

Animal study
The researchers administered the apple extract to mice according to different schedules. If the mice had been adults, they would have received 1.4 grams of extract per dose.

Daily intake of OPCs increased the expression of the protein CXCL10. This effect occurred when the mice were injected with a substance that mimics a viral interferon response. Cells produce CXCL10 after infection. This chemokine attracts immune cells such as natural killer (NK) cells, among other things.

Click on the figure and table below for a larger version.

Human study
The researchers gave adult human subjects 3 grams of Apple Poly daily for several days. The schedule is shown below. They extracted immune cells from the subjects' blood and exposed them in vitro to interferon-alpha.

Neg = no interferon.

The researchers then examined the production of Major Histocompatibility Complex 1 (MHC1) by immune cells. This increased. This is a signal for cytotoxic T cells to attack infected cells. [For NK cells and memory-like NK cells, the situation is more complex.]

The stimulating effect on MHC1 was optimal after 4 days. When the supplementation was stopped, the effect was still present several days later.

Conclusion
"Type I interferones are induced immediately upon sensing viral molecular patterns and are a critical component of innate antiviral immunity", the researchers write.

"Our therapeutic defense against viruses is currently limited to a few antiviral drugs and treatment with type I recombinant interferones."

"Our data suggest that ingested apple polyphenols has long-lasting effects on expression patterns downstream of type I interferones."

"These results support a novel biological effect of oligomeric procyanidins sources in vivo that may be a viable antiviral prophylactic approach."

Pycnogenol? Grape Seed Extract (GSE)?
It's possible that, in addition to supplementation with acai polyphenols, Pycnogenol or GSE also enhances the initial response of the innate immune system.

If this is indeed the case, a significantly lower dose might be required than the dose used in the Montana State University study. The concentration of oligomeric procyanidins in Pycnogenol and GSE is higher than in apple extracts. The bioavailability and half-lives of the oligomeric procyanidins in Pycnogenol and GSE are also higher than those in apples.