Peripheral blood lymphocytes from 15 patients with hypernephroma were stimulated with partially purified tumor plasma membranes to incorporate [3H]thymidine. Kidney tumor and normal kidney membranes were adjusted to antigenic equivalence as determined by their ability to inhibit in the HLA 51Cr microcytotoxicity assay. Membranes from control "normal" kidney adjacent to the tumor stimulated less than did the tumor. Six of eight patients responded to autologous tumor (p less than 0.05). One

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... t responded to allogeneic tumor of the same histological type. The importance of statistical analyses of tumor membrane lymphocyte stimulation data is discussed in relation to the assay system. Sequential studies suggest that this assay may be useful as a guideline for the monitoring of current therapeutic regimens and future immunotherapy. The results of this assay are discussed in relation to other in vitro tumor lymphocyte stimulation assays. The limitations of this assay appear to be two: (a) it can be used only in large tumor systems where there is adequate tissue for analysis and controls; (b) it may detect nontumorous antigens or nonspecific stimulators in allogeneic studies. Further studies are needed to correlate the blastogenic response with the patient's prognosis.