Immunostimulatory effect of kumquat (Fortunella crassifolia) and its constituents, β-cryptoxanthin and R-limonene

Area of Science:

• Immunology
• Nutrition Science
• Stress Physiology

Background:

• Natural killer (NK) cells are crucial for innate immunity, targeting cancer and infected cells.
• Aging and stress impair NK cell activity, increasing disease susceptibility.
• Kumquats are a potential dietary intervention for immune support.

Purpose of the Study:

• To investigate the effects of kumquat consumption on NK cell activity under stress.
• To identify active compounds in kumquats responsible for immune and anti-stress effects.
• To evaluate the impact of these compounds on NK cell function and cytokine production.

Main Methods:

• In vivo study using a restraint stress model.
• Measurement of plasma corticosterone levels and splenocyte cytotoxicity.
• Identification of active kumquat components: β-cryptoxanthin (BCX) and R-limonene.
• In vitro analysis of BCX and R-limonene effects on human NK cell line (KHYG-1) and IFN-γ production.

Main Results:

• Kumquat consumption suppressed stress-induced elevations in corticosterone.
• Splenocyte cytotoxicity, reduced by stress, was restored by kumquat intake.
• β-cryptoxanthin (BCX) and R-limonene were identified as key active compounds.
• BCX and R-limonene, along with R-limonene metabolites, enhanced IFN-γ production in human NK cells.

Conclusions:

• Daily intake of kumquats can mitigate stress and enhance NK cell activity.
• β-cryptoxanthin and R-limonene are bioactive components in kumquats with immunomodulatory and anti-stress properties.
• Kumquats represent a promising natural food source for supporting immune function and stress resilience.