The experiments here described demonstrate morphological changes in the lymphatic tissue of rabbits with corneal xenografts (heterografts) at the time of advanced graft reaction. These changes consist of hyperplasia of lymphoid follicles and enlargement of germinal centers of conjunctiva, lymph nodes, and spleen, as well as lymphocytic reaction in the liver. In rabbits in which the rejection was delayed for two more weeks, with low doses of azathioprine similar but milder changes were observed in the lymphatic tissue before graft rejection, indicating that such systemic alterations can develop in the presence of avascular corneas.
Polack FM, Gonzales CE. The Response of the Lymphoid Tissue to Corneal Heterografts. Arch Ophthalmol. 1968;80(3):321-324. doi:10.1001/archopht.1968.00980050323005