Influence of ocular surface antigen on the postnatal accumulation of immunoglobulin-containing cells in the rat lacrimal gland

Abstract

The objective of the present study was to determine whether antigenic presence on the ocular surface might directly influence the development or expression of the lacrimal secretory immune system. Experiments were designed to: (i) analyse the temporal accumulation of IgA-, IgG- and IgM-containing cells in lacrimal tissue during postnatal development (6-27 days of age); (ii) examine whether prevention of antigenic exposure to the ocular surface by unilateral tarsorrhaphy might inhibit lymphocyte immigration into the ipsilateral gland during development; and (iii) assess whether a non-invasive antigen, after placement on the ocular surface of infant or adult rats, undergoes retrograde transfer to the lacrimal gland. Our results demonstrated that: (i) the accumulation of IgA-, IgG- and IgM-containing cells in lacrimal tissue was most pronounced during the 6-day period after eyelid opening (15 days of age). The pattern of appearance of these Ig-containing cells, which were predominantly IgA-positive, was identical in both left and right lacrimal glands. (ii) Closure of the left lid by tarsorrhaphy from 10 to 18 days of age had no effect on the accumulation of IgA-, IgG- and IgM-containing cells in the left lacrimal tissue compared to cell numbers in the right gland. (iii) Following placement of radiolabelled albumin on the ocular surface, antigen was almost completely cleared within 1-2 hr. Analysis of lacrimal glands showed no significant accumulation of radioactivity at any time-point, either in the presence or absence of ocular inflammation. In contrast, up to 17.8% of radioactivity was found in the stomach 1-2 hr following topical antigen application. Overall, our results show that a rapid development of the lacrimal secretory immune system occurs between 15 and 21 days of age. This process does not appear to be dependent upon local antigenic stimulation. In addition, our findings indicate that a non-invasive antigen, when applied to the ocular surface, does not undergo retrograde transfer to the lacrimal gland. Instead, antigen appears to be cleared primarily through the gastrointestinal tract.