Structural polymeric features that contribute to in vitro immunostimulatory activity of instant coffee

- Data show that instant coffee polymers stimulate both innate and acquired immune system cells in vitro.
- The activity is due to the arabinogalactan rich fractions, as observed in two different brands.
- These fractions stimulate in vitro B lymphocyte, macrophages and dendritic cells.
- α-Chymotrypsin treatment did not affect B lymphocytes activation.
- Arabinofuranosidase treatment decrease B lymphocytes activation.

An instant coffee fraction, rich in arabinogalactans, obtained by ultrafiltration, using 1 and 5 kDa membranes, has previously shown in vitro stimulatory activity on BALB/c mice spleen B lymphocytes. The compounds inducing lymphocytic activation were shown to elute, mainly near the void volume by size-exclusion chromatography, using Bio-Gel P6 (1-6 kDa). Treatment of the compounds with chymotrypsin, a digestive protease, did not affect the induced B lymphocyte activation. On the contrary, hydrolysis with an α-l-arabinofuranosidase, removing single terminally-linked arabinose residues, decreased the extent of B cell activation. The immunostimulatory activity of these compounds was also observed by in vitro experiments, using bone marrow-derived macrophages and dendritic cells as responders. Altogether, these results show the relevance of single arabinose residues, present at the non-reducing end of polymeric compounds, to the coffee stimulatory activity in cells mediating innate and acquired immunity.

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