Development of specific cell-dependent antibody during growth of a syngeneic rat sarcoma

Suppression of humoral and cell-mediated immune responses in vitro by benzo(a)pyrene

The effect of benzo(a)pyrene (BaP) at different molar (M) concentrations on the in vitro anti-sheep red blood cell (SRBC) plaque (antibody) forming cell (PFC) response and the one-way mixed lymphocyte response (MLR) was tested. Inhibition of the PFC response and the MLR occurred when spleen cells were exposed to a wide range of BaP concentrations from 10(-4) M to 10(-8) M. Maximum depression of the responses occurred at 10(-5) M for PFC production (47% of controls) and for the MLR (19% of controls) as measured by a stimulation index. No significant loss in cell viability was observed at this or lower molar concentrations of BaP. The non-carcinogenic analog of BaP, benzo(e)pyrene, did not suppress PFC responses at comparable concentrations. This in vitro system will facilitate manipulations of T and B lymphocytes and macrophages (adherent cells) in a controlled culture environment for precisely characterizing the sensitivity of these cells and their subpopulations on exposure to BaP.

Activation of K cells in mice with transplanted tumours differing in immunogenicity and metastasizing capacity

The effector arm of antibody-dependent cellular cytotoxicity (ADCC) was evaluated using 51Cr-labelled chicken erythrocytes as targets in BALB/c mice transplanted with the Moloney sarcoma virus-induced tumours T-MSV and MS2, and in C57BL/6 mice transplanted with the chemically induced FS6 sarcoma, Lewis lung carcinoma and B16 melanoma. Tumour-bearing animals showed higher levels of ADCC than normal mice, a stimulation confirmed in MS2-bearing mice, using SL2 lymphoma cells as targets in a cytostasis assay. ADCC effector-cell capacity was higher in animals transplanted with the immunogenic, spontaneously regressing T-MSV than in mice bearing the poorly immunogenic metastasizing MS2 sarcoma. The increased ADCC activity detectable in the spleen of tumour-bearing hosts was not abolished by removal of phagocytic-adherent cells.

Cytotoxicity of guinea-pig lymphoid cells against guinea-pig hepatoma cells in tissue culture

The cytotoxic effect of guinea-pig lymphoid cells on guinea-pig hepatoma cell lines in tissue culture was investigated, using the microplate technique of Takasugi and Klein (1970). The effect of lymphoid cells from guinea-pigs immunized against tumor cells was compared to that of cells from normal controls. Several ratios of effector to target cells (10 : 1, 50 : 1, 150: 1, 250 : 1) were used. In Hartley guinea-pigs immunized with allogeneic tumour cells, peripheral blood lymphoid cells from 14/16 animals showed significant cytotoxicity against that tumour in culture. In a syngeneic tumour/host system, 7/13 animals showed cytotoxicity. Spleen cells gave less consistent results in both systems. The cytotoxic activity of subpopulations of immune lymphocytes against tumour cells in vitro was investigated. It was found that although both T-cell-enriched and T-cell-depleted cell populations exhibited cytotoxicity against tumour cells, the unfractionated cell population was the most effective. This suggests that some degree of cell cooperation may be involved in the cytotoxicity. Antibody-dependent cellular cytotoxicity was also obtained. A T-cell-depleted population of normal cells was shown to be cytotoxic to tumour cells in the presence of serum from immune animals. This type of cytotoxicity could be obtained concomitantly with cell-mediated cytotoxicity in the same animals.

The distribution and fate of blood-borne 125IUdR-labelled tumour cells in immune syngeneic rats

Radiolabelled sarcoma cells injected into the tail veins of normal rats were held up almost exclusively in the lung, and were not observed to pass through into the systemic circulation. Intramuscularly injected tumour cells were retained at the site of injection. Radioactivity was lost from both sites though more rapidly from the lung than from muscular tissue and was probably the result of tumour-cell death. Alveolar macrophages did not take part in the destruction of tumour cells in the lung. There was an increased rate of radiolabel loss from the lungs of hyperimmune, post-excision and tumour-bearing rats, as compared with normal rats. The destruction was immunologically specific; it was detected earlier, was more comprehensive in the hyperimmune and post-excision animals than in tumour-bearing animals, and correlated with the ability of the hyperimmune and post-excision animals to reject larger numbers of intravenous unlabelled tumour cells, than the tumour-bearing rats.

Kinetics of serum factors mediating blocking, unblocking and antibody-dependent cellular cytotoxicity in hamsters given isografts of para-7 tumor cells

Sera collected at intervals after PARA-7 tumor-cell inoculation were monitored for blocking, unblocking, and antibody-dependent cellular cytotoxicity (ADCC) using the microcytotoxicity test. Within 7 days after isografting, significant levels of blocking were demonstrated. This activity increased in parallel with tumor growth and reached a maximum at day 21. In contrast, the capacity of the sera to mediate ADCC was maximal at day 7, and no longer detectable at 3 weeks. Unblocking was not demonstrable in tumor-bearer sera. Further studies showed that, when the tumor was exicised, blocking activity fell rapidly while ADCC was elevated. Sera collected 7 days after surgery could neutralize the blocking activity of tumor-bearer sera. Significant levels of unblocking were still evident 10 weeks after surgery while ADCC had generally disappeared after 5 weeks. These findings illustrate the complexity of the hamster's humoral immune response to tumor cells, and suggest that (1) the sequestering of antibody by circulating tumor antigen accounts for the demise of ADCC in tumor-bearer sera and the concomitant appearance of blocking activity; and (2) the serum factors mediating ADCC and unblocking differ.

Characterization of cytotoxic spleen cells and effects of serum factors in a syngeneic rat tumour system

Splenocytes from inbred Wistar rats bearing a syngeneic squamous cell carcinoma (Spl) were fractionated by several techniques to characterize the lymphoid cells cytotoxic to the tumour in vitro. The anti-tumour cytotoxicity is presumably mediated primarily by T lymphocytes because it was greatly reduced by removal of T lymphocytes with heterologous anti-T serum plus complement but not by removal of other cell types. Cytotoxicity could be blocked at the tumour cell but not at the effector cell by sera taken late in tumour growth. Sera taken earlier in tumour growth could induce cytolysis of tumour cells by normal splenocytes but only if the tumour cells were treated with serum and washed before addition of the effector cells. Although splenocytes from normal and tumour-bearing rats were equally effective at lysing antibody-coated target cells it is unlikely that this mechanism is important in vivo as sera from early in tumour growth onwards contained factors (immune complexes?) which inhibited antibody-induced lymphocytolysis.

Significance of arming, potentiating and blocking factors as correlates the tumour-host interaction in the hamster SV40 system

The study of blocking factors requires in vitro assay of cell mediated immunity that parallels the in vivo response. By microcytotoxicity testing, progressor and immune peripheral blood lymphocytes caused significant target cell reduction. The cytotoxicity was specific as no cytotoxic effect was detected against unrelated normal as well as a malignant target cell lines. No anti-tumour effect was noted when progressor peripheral blood lymphocytes were evaluated in the Winn assay. In marked contrast, immune peripheral blood lymphocytes were capable of preventing tumour growth in the Winn assay. Furthermore, hamsters repeatedly immunized with irradiated SV40 tumour cells could resist a live cell challenge. Thus immune peripheral blood lymphocytes were chosen as the effector population to evaluate the abrogation ability of serum in the microcytotoxicity assay.

Antibody-dependent cell-mediated cytotoxicity for human monolayer target cells bearing blood group and transplantation antigens and for melanoma cells

A sensitive assay for antibody-dependent cell-mediated cytotoxicity (ADCMC) was developed utilizing serum from a patient with gestational choriocarcinoma and the 3H-proline microcytotoxicity test for detection fo destruction of monolayer target cells. Conditions for optimal expression of ADCMC were investigated using serum from this patient and skin fibroblasts from her husband and daugther as target cells with semi-purified blood leukocytes from normal donors as effector cells. Factors critical for optimal expression of ADCMC in this assay are the selection of effector cell donors possessing high levels of activity in the presence of serum with known lymphocyte-dependent antibody. (LDA), the effector cell preparative technique, and incubation for up to 40 h. Tris-NH4Cl lysis of red blood cells was found significantly to reduce effector cell activity. Under optimal conditions, the LDA titer of this patient's serum was greater than 10(-4). The sensitivity of the assay was confirmed by the detection of LDA activity of an anti-blood-group antibody at dilutions not demonstrating hemagglutination, and by the induction of ADCMC for blood group A antigen-bearing target cells by normal sera of B and O blood groups. In a preliminary study of sera from 16 melanoma patients on the corresponding antologous tumor target cells, four had significant LDA. Further studies are under way to determine specificty, incidence, and relationship of LDA-positive autologous sera to course of disease.

Serum factors modifying cell mediated immunity to rat hepatoma d23 correlated with tumour growth

Sera from rats bearing a progressively growing transplanted aminoazo-dye-induced hepatoma (hepatoma D23) have been examined for the presence of hepatoma D23-specfic antigen, antibody and immune complexes throughout the course of tumour growth. The levels of these factors have been correlated with the in vitro blocking and inhibition of cytotoxic lymph-node cells from immunized animals for cultured tumour cells. Sera from animals bearing small tumours (7-14 days after tumour implantation contain free tumour-specific antigen whilst immune complexes could not be detected. Although these sera were neither blocking nor inhibitory under the normal conditions of the test, when concentrated two and fourfold, inhibition but not blocking of lymph-node cell cytotoxicity could be detected. In comparison sera from animals bearing large tumours (24-28 days) blocked but did no inhibit in vitro lymph-node cell cytotoxicity and this correlates with the presence of tumour-specific immune complexes in antibody excess. Animals with intermediate-sized tumours had high levels of both blocking and inbibitory activity in the serum, these effects becoming apparent when neither free antibody nor free antigen could be detected. The relevance of these findings to the mechanism by which a growing tumour may escape specific cellular immune destruction is discussed.

Changes in host immunity following excision of a murine melanoma

Changes in cell mediated and humoral immunity following the excision of a transplantable melanoma growing in the footpad of its syngeneic host, as measured by an in vitro cytotoxicity test, were assessed. Spleen cell cytotoxicity did not change significantly. Cells from the regional lymph nodes stimulated tumour growth before tumour excision. Three days following tumour excision this stimulatory effect was undetectable. Loss of serum factors capable of blocking the cytotoxicity of spleen cells occurred 24 h after tumour excision. Serum cytotoxicity increased after tumour excision to a maximum of the third day. Following tumour excision the rise in serum cytotoxicity and loss of regional lymph node tumour stimulation were concomitant with the loss of blocking activity.