ENHANCEMENT OF HUMAN NATURAL KILLER CELL ACTIVITY BY
MODIFIED ARABINOXYLANE FROM RICE BRAN (MGN-3)
INTERNATIONAL JOURNAL OF IMMUNOTHERAPY XIV (i) (1998)
Summary: Arabinoxylane, from rice bran (MGN-3)
was examined for its augmentory effect on human natural killer cell activity
in vivo and in vitro.
Twenty-four individuals were given MGN-3 orally at three
different concentrations: 15, 30 and 45 mg/kg/day for 2 months. Peripheral
blood lymphocyte-natural killer cell activity was tested by 51CR-release
assay against K562 and Raji tumor cells at 1 week, 1 month and 2 months
post-treatment and results were compared with baseline natural killer activity.
Treatment with MGN-3 enhanced natural killer activity
against K562 tumor cells at all concentrations used. In a dose-dependent
manner, MGN-3 at 15 mg/kg/day increased natural killer activity after 1
month post-treatment (two-fold over control value), while significant induction
of natural killer activity at 30 mg/kg/day was detected as early as 1 week
post-treatment (2 1/2 times control value).
Natural killer cell activity continued to increase with
continuation of treatment and peaked (five-fold) at 2 months (end of treatment
period). Increasing the concentration to 45 mg/kg/day showed similar trends
in natural killer activity. However the magnitude in values was higher
than for 30 mg/kg/day.
After discontinuation of treatment, natural killer activity
declined and returned to baseline value (14 lytic units) at 1 month.
Enhanced natural killer activity was associated with an
increase in the cytotoxic reactivity against the resistant Raji cell line.
MGN-3 at 45 mg/kg/day showed a significant increase in natural killer activity
after 1 week (eight-fold) and peaked at 2 months post-treatment (27 times
that of baseline). Culture of peripheral blood lymphocytes with MGN-3 for
16 hours demonstrated to a 1.3 to 1.5 times increase in natural killer
activity over the control value.
The mechanism by which MGN-3 increases natural killer
activity was examined and showed no change in cluster of differentiation
(CD) 16+ and CD56+ CD3+ of MGN-3 activated natural killer cells as compared
with baseline value; a four-fold increase in the binding capacity of natural
killer to tumor cell targets as compared with baseline value; and a significant
increase in the production of lnterferon-y (340-580 pg/mL).
Postculture of peripheral blood lymphocytes with MGN-3
at concentrations of 25-100 pg/mL. Thus, MGN-3 seems to act as a potent
immunomodulator causing augmentation of natural killer cell activity, and
with the absence of notable side-effects, MGN-3 could be used as a new
biological response modifier having possible therapeutic effects against