Abstract
Abstract: :
Purpose: To test whether laboratory measurement of peripheral blood lymphocyte activation can be correlated with the clinical status of high–risk corneal and limbal grafts. Methods: Twenty patients with high–risk corneal and limbal grafts, receiving systemic immunosuppression with tacrolimus, were seen monthly for clinical assessment and serial blood samples. Adverse events identified were active new vascularisation of the graft, old vascularisation, epithelial disturbance, raised IOP, conjunctivitis and loose graft sutures. Samples from 36 age–matched normal subjects were analysed as controls. A stimulation assay was performed to measure the reactivity of peripheral blood lymphocytes to exogenous Interleukin–2, which was assessed by incorporation of tritiated thymidine. Each sample was divided into 8 aliquots, half of which were exposed to Interleukin–2. The stimulation index is the ratio of the IL–2 stimulated counts divided by the unstimulated counts. Results: The mean stimulation index for all patients was markedly reduced compared to controls (mean 18.07 c.f. 68.93; P < 0.0001, unpaired t–test). The stimulation index for grafts with active new vascularisation (mean 24.67) was increased both compared to baseline grafts with no adverse event (mean 15.80; P = 0.03, unpaired t–test) and those with inactive old vascularisation (mean 14.51; P = 0.04, unpaired t–test). On paired analysis, there was a significant difference between the stimulation indices at the time of an adverse event compared with the preceding baseline value (p < 0.01, paired t–test) and the subsequent baseline value in the same patient (p < 0.05, paired t–test). Conclusions: Changes in peripheral blood lymphocyte activation in high–risk corneal and limbal grafts, measured by stimulation assay, correlate with the clinical status of the grafts. These laboratory data may be helpful in making decisions regarding the duration of systemic immunosuppression.
Keywords: cornea: clinical science • transplantation • cornea: basic science