In the present study, we have investigated the effects of
phycocyanin, a biliprotein of Spirulina platensis, on mucosal and systemic immune responses and allergic
inflammation in C3H/HeN and BALB/cA mice. To induce the
antigen-specific
antibodies in the peripheral lymphoid tissues such as Peyer's patches and mesenteric lymph nodes, biodegradable
ovalbumin-entrapped
poly (DL-lactide-co-glycolide) particles were used as an
antigen. Two weeks after the onset of
phycocyanin ingestion, mice were immunized with an aqueous
ovalbumin (OVA)
solution. Starting at one week after the primary immunization, the mice were subjected to oral immunization with the biodegradable OVA microparticles twice a week.
IgA,
IgE and
IgG1 antibodies were determined by ELISA. The OVA microparticles of 4-microm diameter successfully induced
antigen-specific
antibodies. In the mice that received
phycocyanin treatment for 6 wk, a marked increase in the
antigen-specific, as well as the total,
IgA antibody level was observed in the Peyer's patches, mesenteric lymph nodes and intestinal mucosa as well as in the spleen cells. Both
antigen-specific
IgG1 and
IgE antibody levels in the serum were suppressed by ingestion of
phycocyanin for 8 wk. However,
inflammation of the small intestine, monitored as vascular permeability by the
Evans blue-leaking method was reduced by
phycocyanin at 6 wk, which preceded the suppression of
antigen-specific
IgG1 and
IgE antibody production by 2 wk. These results suggest that
phycocyanin enhances
biological defense activity against
infectious diseases through sustaining functions of the mucosal immune system and reduces allergic
inflammation by the suppression of
antigen-specific
IgE antibody.