Recent studies on the assessment of cell-mediated cytotoxicity in vitro

Experiments employing two new methods for the in vitro assessment of cell-mediated immunity against neoplastic target cells are indicated. Both methods offer the advantage of rapid and quantifiable determination of very early events in cell-cell confrontations. One technique measures the incorporation of precursors of proteins, RNA, and DNA synthesis by neoplastic cells incubated with effector cells during the first hours of contact. It was found that exposure of BALB/c plasmacytoma (PCT) cells to splenocytes from PCT-sensitized donors failed to bring about inactivation of the target cells or their release of 51Cr during several hours of interaction. However, inhibition of 3H-thymidine incorporation was almost instantaneous and pronounced. This observation suggests that cytostatic events may transpire in cell-cell interactions in the absence, or before the onset, of lethal changes. The second method assays the specific adherence of 51Cr-labeled lymphoid cells from Rous sarcoma (RS)-bearing chickens to RS target cells. This immunoadherence test revealed perferential, specific reactivity in autochthonous as compared with allogeneic interactions, which indicated recognition of individual-specific tumor-associated antigens against a background of strongly expressed group antigenicities.