Association of uveal melanocyte destruction in melanoma-bearing swine with large granular lymphocyte cells.

Sinclair strain miniature swine spontaneously develop and regress malignant melanoma lesions, with uveitis and vitiligo occurring subsequent to tumor regression. Peripheral blood lymphocytes (PBL) of Sinclair swine undergoing tumor regression and melanocyte destruction demonstrated significant lytic activity against K562, porcine semiallogeneic uveal melanocytes, and melanoma cells in 4-h chromium release assays. The ability of porcine PBL to lyse these target cells appears to be an age-associated immune response, as evidenced by the relative inability of PBL of pigs less than 4 weeks old to lyse target cells. In young adult pigs, however, PBL cytotoxic activity significantly increases; piglets 6 weeks old and older demonstrate efficient killing of all three targets. Conjugate formation assays demonstrate that a lymphoid effector cell possessing large granular lymphocyte (LGL) morphology may be involved in melanocyte destruction. These findings suggest that a LGL subpopulation may participate in melanoma and melanocyte destruction which can induce a uveitic syndrome in Sinclair swine with melanoma.