[Histological examination of lymphoid follicles in conjunctiva-associated lymphoid tissue in guinea pigs--Report 1. Histological characteristics of follicular dendritic cells].

We histologically examined the existence of follicular dendritic cells (FDCs) in the follicular area of conjunctiva-associated lymphoid tissue (CALT). Animals used in the experiment were Hartley guinea pigs sensitized with a topical application to the eyes of an emulsion of a mixture of ovalbumin and Freund's complete adjuvant in equal amounts. The animals were divided into 4 groups: a group with no eye drops administered (Group A), a group examined 1 week after administration of eye-drops (Group B-1), a group examined 2 weeks after administration (Group B-2), and a group given booster administration of eye-drops (Group C). These animals were examined by methyl green pyronine staining, alpha-naphthylacetate esterase staining, and enzyme-antibody methods against S-100 protein or major histocompatibility complex class II (MHC class II) antigen. Also peroxidase-anti-peroxidase (PAP) was applied to the eyes and the uptake of PAP in CALT was observed histologically. In each group, positive reticular stains to alpha-naphthyl-acetate esterase staining and S-100 protein were found in the CALT follicular area. The positive cells were found to be dendrite cells by immunoelectron microscopy. An uptake of PAP was seen in the CALT follicular area, suggesting the function of trapping and holding the antigen-antibody complex by FDCs. It was concluded that dendritic cells present in the follicular area of CALT were FDCs.