SCARCITY OF GAMMA-DELTA T-CELLS IN INTESTINAL EPITHELIA CONTAINING COCCIDIA DESPITE GENERAL INCREASE OF EPITHELIAL LYMPHOCYTES

Lymphocytes of intestinal epithelia were examined in lambs experimenta lly infected with coccidia. Fourteen conventional, coccidia-free 3-wee k-old lambs of the Dala breed were given either 250,000 (eight lambs i n experiment 1) or 100,000 (six lambs in experiment 2) sporulated oocy sts of Eimeria ovinoidalis (>99.9% pure) via a stomach tube. Nine lamb s (five in experiment 1 and four in experiment 2) of the same age serv ed as uninoculated controls. The infected lambs developed diarrhea and dehydration between days 10 and 13 after infection. Intestinal specim ens were collected 10-20 days after inoculation. A heavy multifocal in fection of the epithelium comprising schizonts, gamonts, and oocysts r esulted, with changes being most pronounced in the large intestine and the terminal part of ileum. Lesions included villous atrophy, villous fusions, and crypt hyperplasia. Computer-assisted morphometric analys is was applied to immunoperoxidase-stained sections for quantification of intraepithelial T cell subsets and included the distal jejunum of lambs of experiment 1. A significant increase in the epithelial area o f the distal jejunum occupied by CD8+ lymphocytes was found in the inf ected lambs as compared with uninfected controls (18.3% versus 3.7%). The increased presence of CD8+ cells may be of significance in the int estinal immune response to ovine coccidiosis. A moderate, overall incr ease was also found for the gamma delta lymphocytes in the jejunal epi thelium. Examination of the ileum of infected lambs of both experiment s showed a scarcity of gamma delta cells (0.4% of epithelial area) in stretches of epithelium infected by coccida as compared with adjacent noninfected epithelium (4.0% of epithelial area). The significance of this negative association between gamma delta T cells and infected epi thelial cells in ovine coccidiosis is unknown.