Suppression of experimental allergic conjunctivitis in guinea pigs by oral administration of antigen

Feeding antigen can induce an immunological unresponsiveness termed oral tolerance. The authors examined the effect of the oral administration of two antigens, ovalbumin (OVA) and cedar pollen extract (CPE) on experimental allergic conjunctivitis in guinea pigs quantitatively. After the primary active immunization with either OVA or CPE, guinea pigs were given each antigen orally everyday. After five antigen injections, conjunctivitis was elicited by the instillation of the antigen eye drops. The early phase of allergic reaction was evaluated by measuring the leakage of Evans blue injected intravenously. The later inflammation was evaluated by the number of infiltrating leukocytes. Oral administration of both OVA and CPE significantly reduced conjunctival exudation. Cellular infiltration was also markedly diminished in the OVA-fed group. Serum levels of anti-OVA IgE and anti-CPE IgE antibodies were suppressed by feeding of each antigen, and there was a positive correlation between the IgE level and the amount of dye leakage. This result suggests that the conjunctivitis was suppressed because of the inhibition of antigen-specific IgE production.