Expression of CD23/CD21 and CD40/CD40 ligand in vernal keratoconjunctivitis

Purpose The overproduction of immunoglobulin E (IgE) antibodies is associat ed with vernal kerato conjunctivitis (VKC). CD23/CD21 and CD40/CD40 ligand (CD40L) interactions have been proposed to be involved in the regulation of IgE synthesis. The purpose of the present study was to investigate the pre sence and distribution of CD23, CD21, CD40 and CD40L in the conjunctiva fro m patients with active VKC. Methods Conjunctival biopsy specimens from 8 subjects with active VKC and 6 control subjects were studied. We used immunohistochemical techniques and a panel of monoclonal antibodies (mAbs) directed against CD23, CD21, CD40 a nd CD40L. In addition, a panel of mAbs were used to characterise the compos ition of the inflammatory infiltrate. Results In the normal conjunctiva, basal epithelial cells and vascular endo thelial cells in the upper substantia propria showed a constitutive very we ak immunoreactivity for CD40. The immunoreactivity for CD23, CD21 and CD40L was absent, In VKC specimens, the stromal inflammatory infiltrate was orgn anised as a diffuse infiltrate and as small lymphoid follicles consisting o f CD20(+) B lymphocytes intermingled with smaller numbers of CD3(+) T lymph ocytes, and CD68(+) monocytes/macrophages. Lymphocytes in the centre of the lymphoid follicles showed CD23 and CD21 immunoreactivity. CD40 immunoreact ivity in epithelial cells and vascular endothelial cells was stronger in VK C specimens than in control eyes. Furthermore, the majority of mononuclear cells, including T and B lymphocytes, showed immunoreactivity for CD40. CD4 0L immunoreactivity was not detected. Conclusion B lymphocytes in the lymphoid follicles expressing CD23, CD21 an d CD40 are activated and might be precursors of IgE-producing B cells. Thes e results suggest that the conjunctiva might contribute to IgE synthesis.