Problems in the use of in vitro assays for monitoring cell-mediated immunity in cancer patients.

Considerable controversy has evolved about the relevance of microcytotoxicity assays (both visual methods and isotope release assays) in the studies of cell-mediated immunity in human tumor systems. A stage has been reached, where technical aspects of these assays, capable of influencing the results, need to be considered: tumor target cell selection (the use of cells from short term cultures or cell lines), lymphocyte isolation procedures (composition of the effector cell populations) and selection of baseline controls for expressing the results, are recongnized as potential variables influencing results of in vitro cell-mediated cytotoxicity assays.