Tumour-infiltrating lymphocytes in primary melanoma: functional consequences of differential IL-2 receptor expression

Abstract

SUMMARYTumour-infillraling lymphocytes (TIL) have been isolated from early priniarv melanoma (Clark level 111) and expanded in vitro using culliirc conditions wiih low concentraiions of lL-2 (50 U/ml). Immediately after isolation TIL consisted of mainly CD3' T cells, and the portion of CD56 + natural killer (NK) cells was below 20%. Fresh TIL cultures could be distinguished by CD25 expression since some contained up lo 33' Vn. others less than 5"A. CD25 ' cells. These showed differences in subsequent development during/rt )•///•() expansion. CD25-cxpre,ssingcultures remained stable in their phenotype. whereas the second TIL type showed major changes: CD3 (ca 1Q-7>{}"A.) expression decrease. CD25 (ca 5-35'^) and CD56 (ea 15-S5'Vu) expression increase. The TIL type, which remained dominated by CD3^ T eells, killed autologous tumour cells efficiently (^'Cr-rclease greater than 3O''a at a E/T ratio of 20:1). which could be blocked by MoAbs against MHC class 1 molecules. In contrast, the other TIL typcexhibited weak cytotoxicity(less than 17"-., ''Cr-releaseal an E/T ratio of 20:1) against the autologous tumour. Therefore, the expression of CD25 on freshly isolated TIL is a good marker for tumour specificity of in vitro expanded TIL.