Spontaneous variations in the cell population of a T-cell lymphoma during tissue culture and transplantation.

Immunologically induced T-cell lymphomas were kept for long periods of time in isotransplantation and in tissue culture. Initially, a certain number of cells within the tumor showed differentiation towards histiocytes. These disappeared completely after about the twentieth graft generation when the tumor changed toward a more atypical and more uniform neoplasm. That change was correlated with a decrease in transplantability, a limited growth in tissue culture, and a decrease in density of theta antigens on tumor cell membranes. While the original tumor and early grafts contained occasional C-type particles, these were never demonstrated in late tumor grafts. The possible implications of these changes are discussed.