The surface ultrastructure of normal and leukemic rat lymphocytes.

In studies on the nature of the malignant state, there has been increasing interest in the external surface of cancer cells. Coman and his co-workers (1, 2, 5) established the fact that the intercellular adhesiveness of malignant cells was lower than that of their normal prototypes and that this difference probably played a major role in the invasive characteristics of cancer cells. Since ad hesiveness is a surface phenomenon, it seemed reasonable that some morphological difference in surface structure might be demonstrable at the ultramicroscopic level, and, in 1955, Coman and Anderson (3) reported a difference between the surface ultrastructure of malignant and normal rabbit epithelial cells. It is possible that these structural changes are directly related to the decreased adhesiveness of cancer cells. On the other hand, these surface alterations may be independent of adhesiveness and reflect some other characteristics of neoplastic cells. To examine these possibilities, a cell system was needed in which the adhesive characteristics of the normal and malignant cell types were the same, thus separating adhesiveness from other aspects of neoplasia. Normal and leukemic lym phocytes provide such a system, since the ad hesiveness of both cell types is low; that is, they both readily detach from their fellows and enter the circulation as individual cells. Consequently, a comparison was made of the surface ultrastruc ture of normal and leukemic lymphocytes from both the blood and lymph nodes of Wistar rats.