No abstract

The cytotoxicity in vitro of peripheral blood lymphocytes from 54 patients with transitional cell carcinoma of the urinary bladder (TCC-bladder) against a small panel of allogeneic target cells was studied by the "'Cr-release assay. Lymphocytes f r o m 20 patients with other neoplastic diseases, mainly urogenital cancers, were used as controls. Also included were lymphocytes from 24 healthy donors. Lymphocytes f r o m individual donors of all three groups were frequently cytotoxic t o any one of the target cell types on the panel and occasionally this cytotoxicity was high. However, lymphocytes f r o m TCC-bladder patients who were untreated for their disease had an elevated mean cytotoxicity against cells from t w o different cell lines of TCC-bladder origin as compared with that against other target cells, derived either from normal bladder epithelium, from colon qarcinoma o r from malignant melanoma. The cytotoxicity against TCC-bladder targets of lymphocytes from the clinical controls (who were untreated for their cancer) was not significantly elevated over that against the other targets. The same was true for the healthy donors. Lymphocytes f r o m TCC-bladder patients treated with radiotherapy f r o m 1-12 years before testing also had an elevated mean cytotoxicity against TCCbladder targets. This group (31 patients) was heterogeneous, comprising patients with a generally reduced cytotoxicity and others whose lymphocytes were strongly cytotoxic t o TCC-targets. However, while no correlations between cytotoxlcity t o TCCbladder targets and targets of other origin were seen for the untreated patients, the treated TCC-bladder patients showed a positive correlation between cytotoxicity t o TCC-bladder targets and normal " bladder targets. Taken together, the results indicate that lymphocytes of most (but not all) donors was selective, i.e. individual donors' lymphocytes were cytotoxic for some target cell types but not for others. Inspection of cytotoxicity profiles suggests that these selective reactions reflect multifactorial immune responses against a variety of antigens. In addition, in TCC-bladder patients there exists a superimposed cytotoxicity, probably reflecting reactions against one o r several tumor-associated antigens. In treated patients this may be masked by a higher incidence o f cross-reactions, o r by a generally suppressed reactivity. Finally, the results also emphasize the importance of using age-and sexmatched controls for assessing the relative cytotoxicity of different groups of lymphocyte donors.

In humans T cells with surface receptors for the Fc fragment of IgG (Fc gamma receptors) (TG cells) are effector cells in antibody-dependent cellular cytotoxicity (ADCC) and in natural cytotoxicity. While Fc gamma receptors are required to mediate ADCC, their role in natural cytotoxicity is unknown. To investigate this question, Fc gamma receptors on effector cells were modulated by interaction with IgG immune complexes. As a consequence of this modulation, TG cells lost most of their ADCC activity but retained a significant part of their natural killer activity. Thus, these experiments demonstrate that the cytotoxic mechanisms exerted by the same cell population can be dissociated experimentally. Furthermore, they suggest that the net natural cytotoxicity of normal human lymphocytes in certain effector cell-target cell combinations is the result of distinct types of reaction.

Antibody dependent lymphocyte (K cell) mediated lysis of tumor cells in vitro was used to assay for cell surface associated carcinoembryonic antigen (CEA) and two CEA-related normal tissue components, "normal glycoprotein" (NGP) and biliary glycoprotein I (BGP I). Three tumor cell lines were used as target cells. These were HT-29, colon carcinoma, T-24, urinary bladder transitional cell carcinoma and Mel-1, malignant melanoma. To induce lysis we used the IgG-fraction of specific rabbit and monkey anti-CEA sera and of specific rabbit anti-NGP and anti-BGP I sera, respectively. Purified human lymphocytes were used as effector cells. HT-29 was efficiently killed by low concentrations of rabbit anti-CEA and less efficiently by monkey anti-CEA. T-24 and Mel-1 were not lysed by anti-CEA, HT-29 and T-24 were lysed by low concentrations of anti-BGP I. In contrast only HT-29 was lysed by anti-NGP. Only a fraction of the tumor cells was killed by the different antisera although kinetic studies showed that the lytic reaction was complete well before the end of the eighteen hour incubation period used in the assay. Anti-CEA and anti-BGP I gave 30-40% corrected lysis of HT-29. With anti-NGP the corresponding figure was 10-20%.

Blood lymphocytes from small groups of patients with transitional-cell carcinoma of the urinary bladder (TCC), clinical controls (CC) or healthy donors (HD) were tested for cytotoxicity in vitro by a 51Cr-release assay. The target cells were either from TCC or control tissue (long-term cultures) or were from short-term TCC cultures, kept in vitro for 10-20 transfer generations. When tested with allogeneic target cells from long-term cultures, TCC patients' lymphocytes tended to be more cytotoxic to TCC targets than to control targets. For the control lymphocytes this was not seen. A large proportion but not all of the cytotoxicity to these target cells was due to immunoglobulin-dependent cellular reactions, probably mediated by natural and disease-related antibodies of the lymphocyte donors, since it was significantly inhibited by Fab-fragments of rabbit antibodies to human immunoglobulin. Moreover, it was, to a large extent, mediated by lymphocytes with Fc-receptors for IgG. For seven of the TCC target cell cultures (two long-term and five short-term) autologous lymphocytes were also available for testing. While two patients were non-reactive to their own tumor cells, five reacted strongly in the autologous combinations. These autologous reactions were immunoglobulin-independent and were mediated by Fc-receptor-negative effector cells. In some instances, autologous cytotoxicity was accompanied by similar reactions to some of the allogeneic TCC targets but not to the allogeneic non-TCC control targets. On the basis of available information on HLA antigens in this material, the pattern of cross-reactions suggests that the cytotoxicity encountered in the autologous and in some of the allogeneic TCC-combinations may be the expression of antibody-independnet but specific CTL-mediated reactions, regulated by HLA. However, at the present stage of the investigation, other mechanisms must also be considered since the target cells from short-term TCC cultures were sometimes lysed by control lymphocytes in immunoglobulin-independent reactions. Whatever the explanation, the results show that the cytotoxicity observed in the in vitro systems is usually the net result of several different types of reaction. Which effector cell types and which mechanism of recognition will predominate in a given lymphocyte/target cell combination is greatly influenced by the nature and origin of the target cells used.