Phenotypic heterogeneity and cytotoxic activity of Con A and IL-2-stimulated cultures of mouse Thy-1⁺ epidermal cells

Short-term and long-term cultures of mouse Thy-1⁺ epidermal cells (EC) were established in order to characterize their phenotypic and functional properties. Concanavalin A (Con A) and Interleukin 2 (IL-2) stimulated Thy-1⁺ EC mediated non-MHC directed cytotoxicity preferentially against the NK-sensitive target, YAC-1 vs the NK-resistant target, P815; these cells also mediated antibody-dependent cell-mediated cytotoxicity (ADCC), indicating the presence of IgG-FcR on at least some of them. Freshly isolated Thy-1⁺ EC failed to lyse YAC-1 targets; however, this activity was observed after 9 d of culture with Con A and IL-2. While dendritic Thy-1⁺ EC, in vivo, do not express the T-cell markers, L3T4 and Lyt-2, short-term cultured cells displayed phenotypic heterogeneity with small but significant percentages of Lyt-2⁺ and L3T4⁺ cells appearing transiently. The phenotype of the effector cell(s), which mediates cytotoxic activity, was determined by utilizing flow cytometry to sort short-term cultured EC into positively and negatively stained populations. Cells which express L3T4, or which lack asialo GM₁, did not lyse YAC-1 targets; maximum cytotoxic activity was found within populations of cells which are asialo GM₁⁺, Lyt-2^-, and asialo GM₁⁺, Lyt-2⁺. These studies indicate that Thy-1⁺ cells derived from mouse epidermis when cultured in the presence of Con A and IL-2 have the capacity to generate a phenotypically heterogeneous population, some cells of which are capable of mediating cytotoxic activities.