The effect of immunization route and sequence of stimulation on the induction of IgA antibodies in tears.

The capacity of ocular/topical (OT) or gastrointestinal (GI) immunization routes alone or sequentially to elicit and maintain tear IgA antibody responses was assessed in the rat model. Seven days after each biweekly immunization with dinitrophenylated type-III pneumococcal vaccine, the IgA antibody levels in serum, saliva and tears were measured. All groups generally lacked serum IgA responses and eventually possessed similar salivary response frequencies with OT, OT/GI and GI groups showing a tendency for increased salivary IgA antibody levels. Tear IgA antibody responses in all groups were comparable after the third immunization. Subsequently the OT group displayed a gradual reduction in response frequency with a significant drop in IgA levels after the sixth immunization. The OT/GI group maintained tear IgA response frequencies while displaying a significant increase in tear IgA antibody levels; the GI and GI/OT groups maintained tear IgA antibody responses. These data demonstrate that the immunization route and sequence of stimulation have a marked impact on the expression of IgA anti-DNP antibodies in tears.