Inhibitory effect of unicellular green algae (Chlorella vulgaris) water extract on allergic immune response

Background: Chlorella is used as a functional food in East Asia and has been shown to enhance immune system function. However, there has been no direct evidence of the suppressive effect of a hot water extract of Chlorella vulgaris (CVE) on histamine-mediated allergic responses. Results: The antihistamine activity of CVE was analysed using rat peritoneal mast cells (RPMCs) stimulated by compound 48/80. For in vivo verification, ovalbumin (OVA)-immunised BALB/c mice were treated with CVE orally. Serum immunoglobulin E (IgE) levels and splenocyte cytokine levels were determined by enzyme-linked immunosorbent assay (ELISA). CVE prevented histamine release through degranulation of mast cells by blocking the uptake of extracellular Ca²⁺ into RPMCs. Moreover, CVE administration inhibited serum IgE overproduction by OVA via induction of T helper 1 (Th1) skewing that was dependent on interferon-γ (IFN-γ) and interleukin 12 (IL-12) secretion. Conclusion: The results of this study clearly demonstrate that CVE acts as an antiallergic dietary agent by suppressing histamine release via its enhancive effect on Th1-related responses.