The T cell receptor in normal and inflamed human conjunctiva

The majority of human peripheral blood and lymphoid tissue T cells express the TCR alpha/beta heterodimer, while the TCR gamma/delta is expressed on only a small subset of T lymphocytes. However, the majority of murine intraepithelial lymphocytes and most Thy-1+ murine dendritic epidermal cells express the TCR gamma/delta. Selective homing of avian TCR gamma/delta bearing lymphocytes to the intestinal epithelium also has been shown. These findings have suggested that these cells play a role against transformation and infection. More recently, a role in autoimmunity also has been proposed. We examined normal human conjunctiva and inflamed conjunctiva from patients with ocular cicatricial pemphigoid (OCP), an autoimmune disorder, and atopic keratoconjunctivitis (AKC). The majority of T cells in the epithelium and substantia propria of normal conjunctiva expressed the TCR alpha/beta. Tropism of TCR gamma/delta-expressing lymphocytes to normal human conjunctiva was not present. However, in OCP, there was a statistically significant increase in the absolute number of TCR gamma/delta cells/mm2 (epithelium, 33.9 +/- 10.5 [mean +/- standard error of the mean] vs. 159.9 +/- 51.5, P = less than 0.0008; substantia propria, 4.1 +/- 0.9 vs. 240.1 +/- 191.3, P less than 0.002) and TCR gamma/delta cells as a percentage of CD3+ cells (epithelium, 0.18 +/- 0.06 vs. 0.39 +/- 0.07, P = less than 0.02; substantia propria, 0.10 +/- 0.05 vs 0.33 +/- 0.08, P = less than 0.03). This was not the case for AKC. These findings suggest that TCR gamma/delta lymphocytes play a specific but undefined role in certain conjunctival inflammatory conditions and may be important in autoimmunity.