Lymphocyte subgroups and natural killer cell activity in recurrent herpetic stromal keratitis

Although the role of natural killer cells in the defense against certain viral infections has been published, little is known about the role of lymphocyte subgroups in recurrent herpetic stromal keratitis. Accordingly, serum levels of major immunoglobulins (IgG, IgA, and IgM) and IgG subgroups, the lymphocyte subgroups, and natural killer cell activity were investigated in patients with recurrent herpetic stromal keratitis.

Eleven patients with recurrent herpetic stromal keratitis and 10 healthy subjects were included. A delayed-type hypersensitivity skin test was performed in addition to the determination of serum immunoglobulin levels, IgG subgroups, peripheral blood lymphocyte percentages, and natural killer cell activity in both groups.

The result of the delayed-type hypersensitivity skin test was positive in all patients with recurrent herpetic stromal keratitis and healthy subjects. No significant difference was obtained in serum immunoglobulin levels and IgG subgroups between the patients and healthy subjects. Among the cell surface antigens (CD3, CD4, CD8, CD16, CD19, and CD20), only CD8+ (i.e., cytotoxic) T-lymphocyte percentages were significantly increased (P=0.003), and the CD4:CD8 ratio was significantly decreased in the patients compared to the healthy subjects (P=0.021). There was no significant difference in the expression of CD16+ natural killer cells between both groups, despite a significantly lower natural killer cell activity in patients with recurrent herpetic stromal keratitis (P=0.011).

These results indicate that human cytotoxic T cells show a difference in numbers and natural killer cell activity that may affect the prognosis of recurrent herpetic stromal keratitis.