Arabinogalactan proteins contribute to the immunostimulatory properties of New Zealand honeys.
BACKGROUND
Factors in honey that improve wound healing are poorly understood, but are thought to include lipopolysaccharide (LPS), apalbumin-1 and -2, and a 5.8 kDa component that stimulate cytokine release from macrophages.


OBJECTIVE
To characterize the ability of New Zealand honeys to elicit the release of tumor necrosis factor-α (TNF-α) from monocytic cell lines as a model for early events within a wound site.


METHODS
The ability of kanuka (Kunzea ericoides), manuka (Leptospermum scoparium), and clover (Trifolium spp.) honeys to stimulate the release of TNF-α from monocytic cell lines THP-1 and U937 was assayed by ELISA.


RESULTS
All three honeys stimulated TNF-α release from THP-1 cells, with kanuka honey being the most active. The activity of kanuka honey was associated with a high molecular weight (>30 kDa) component that was partially heat labile and inhibitable with polymyxin B. LPS concentrations in the honeys were too low to adequately explain the level of immunostimulation. The contribution of type II arabinogalactan proteins (AGPs) we recently identified in kanuka honey was tested, as AGPs are known immunostimulators. AGPs purified from kanuka honey stimulated the release of TNF-α from THP-1 and U937 cells.


CONCLUSIONS
Here we demonstrated that AGPs we recently identified in kanuka honey have immunostimulatory activity. We propose that the immunostimulatory properties of individual honeys relate to their particular content of LPS, apalbumins, the 5.8 kDa component and AGPs.


CONCLUSIONS
The immunostimulatory activity of kanuka honey may be particularly dependent on AGPs derived from the nectar of kanuka flowers.
The New Zealand Institute for Plant & Food Research Limited, Mt Albert, Auckland, New Zealand. s.gannabathula@auckland.ac.nz
Swapna
S
Gannabathula
Margot A
MA
Skinner
Douglas
D
Rosendale
Jeffrey M
JM
Greenwood
Anthony N
AN
Mutukumira
Gregor
G
Steinhorn
Jonathan
J
Stephens
Geoffrey W
GW
Krissansen
Ralf C
RC
Schlothauer
D000900:Anti-Bacterial Agents / Q000494:pharmacology; D006722:Honey; D006801:Humans; D007155:Immunologic Factors / Q000737:chemistry / Q000494:pharmacology*; D031648:Kunzea / Q000737:chemistry; D031649:Leptospermum / Q000737:chemistry; D008070:Lipopolysaccharides / Q000494:pharmacology; D029902:Medicago / Q000737:chemistry; D009520:New Zealand; D011112:Polymyxin B / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology* / Q000378:metabolism; D020298:U937 Cells
D000900:Anti-Bacterial Agents; D007155:Immunologic Factors; D008070:Lipopolysaccharides; D014409:Tumor Necrosis Factor-alpha; D011112:Polymyxin B