Carbohydrate Matrix of the Epithelial Cell Inclusion in Trachoma

Abstract

Since the discovery by Prowazek and Halberstaedter of the epithelial cell inclusion in the conjunctiva of patients with trachoma, a voluminous literature has appeared on this structure. The great majority of the reports have been devoted to affirming or denying that the inclusion body is actually the causative agent of the disease, and little has been done on its composition and nature. The present study, therefore, was undertaken to ascertain certain chemical characteristics of inclusion.

It was found that the inclusion body contains a carbohydrate to a great extent so that when preparations are flooded with Lugol solution, the inclusion gives a sharp color reaction and appears as reddish brown or dark amber against the contrasting yellow background of the epithelial cell. Evidence has been obtained which indicates that the carbohydrate is glycogen, and that it exists in part as a matrix or diffused throughout the inclusion. This evidence consists of (1) preparations of glycogen fixed on a slide with glycerine exhibit similar staining reactions; (2) fading or disappearance of color of iodine-stained inclusions in unfixed preparations on heating, but reappearing with cooling; (3) disappearance or fading of color reaction in 12 to 18 hours in unfixed preparations without reappearing even after restaining with iodine, thus showing solubility of the color reacting substance in water or saline, in contradistinction to amyloid which may give a similar reaction to iodine; (4) rapid fading of the stained inclusion in fixed preparations when treated with concentrated H₂SO₄ or HCl, both of which intensify the iodine-stained amyloid; (5) digestion and disappearance of inclusion in fixed smears under the action of saliva; (6) in mountings of epithelial scrapings in very weak iodine solution, the red-brown color of the epithelial inclusions disappears when diluted ammonia water is allowed to pass under the cover slip, just as a glycogen solution in the test tube colored with iodine solution will lose its deep red-brown color on addition of ammonia.