Effects of chlorella in OVA-sensitized BALB/c mice

Chlorella has been reported to have various physiological activities, including antiarteriosclerotic, cholesterol-lowering, anti-inflammatory, and immunoregulatory effects. However, there has been no report on the long-term effects of chlorella ingestion on immunity. In the present study, 4- to 10-week-old (young) and 4- to 50-week-old (old) female BALB/c mice were sensitized or not with ovalbumin (OVA), and given basic diet containing chlorella powder at 2% or basic diet alone. The effects of chlorella ingestion on immunity were investigated by measurement of splenic cytokines and immunoglobulin (Ig), analysis of T- and B-cells in the spleen and small intestine by flow cytometry, and analysis of the liver by DNA microarray. Results were compared between the young and old, OVA-sensitized and -nonsensitized, and chlorella and non-chlorella ingestion groups. Production of interferon- (IFN-) was maintained in the nonsensitized old groups, and ratios of T-helper type 1 (Th1) to T-helper type 2 (Th2) cells were similar in the young and old groups. In addition, overproduction of OVA-specific Igs due to OVA sensitization was strongly suppressed, and significant immunotolerance was exhibited irrespective of age. In addition, suppression of T-cell decreases in the spleen due to aging and suppression of changes in T- and B-cells due to OVA sensitization in the small intestinal lymph were demonstrated on flow cytometric analyses. On DNA microarray analysis, immune-related terms including IL11 and major histocompatibility complex (MHC) class 1 were detected, and expression of genes was shown, which were related to IL1-linked genes and complex involving macrophages from the pathways of cytokines and inflammatory response. In addition, suppressions of declined lipid metabolism and energy production were also suggested. Although how the ingredients in chlorella were involved in these changes is unclear, our findings suggest that prevention of decrease in acquired immunity by aging and induction of strong immunotolerance occurred following chlorella ingestion.

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