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The kinetics of "sarcoma" cell appearance and inflammatory cell infiltration into primary Moloney sarcoma virus (MSV>induced tumors has been studied in normal and partially immunosuppressed anti-lymphocyte-globulin (ALGPtreated W y S n mice. The ALG treatment facilitated an earlier appearance of gp7O-positive "sarcoma" cells accompanied by an intense inflammatory response. Time course pulse-labelling studies showed that a decreasing proportion of gp7O-positive "sarcoma" cells were incorporating ['HI-thymidine in vivo in both normal and immunosuppressed mice as the lesion progressed to maximum size. ALG-treated mice inoculated with MSV were given a single injection of ['HI-thymidine immediately prior t o extensive appearance of gp7O-positive "sarcoma" cells (day 6) and were studied for the presence of labelled gp7O-positive cells 2 h, 2 days and 6 days post labelling. The data indicate that few cells divided during the time in which an 8-to 10-fold increase in virus-positive "sarcoma" cell number occurred. These experiments provide evidence that recruitment rather than proliferation of virus-positive cells occurred. The results also suggest that, within the tumor, defense mechanisms develop which restrict sarcomacell proliferation also in ALG-treated mice. The composition of inflammatory cells during the course of tumor progression and regression in the uncompromised mice revealed that the proportion of lymphocytes was highest early and late during tumor development, dropping to a minimum at the peak size of the tumor.Macrophages and granulocytes constituted 70-80 YO of the total cells recovered at peak tumor size and the onset of regression. In the ALG-treated mice, the proportions of macrophages, granulocytes, and infrequent lymphocytes remained constant throughout the duration of the tumor progression. A decrease in total cells, including a decrease in gp7O-positive cells, was noticed before a change in the proportion of infiltrating lymphocytes occurred due to recovery of the immune system. The composition of the inflammatory cells at onset of regression suggests that macrophages and granulocytes are of major importance in the defense against MSV infection.
The kinetics of "sarcoma" cell appearance and inflammatory cell infiltration into primary Moloney sarcoma virus (MSV>induced tumors has been studied in normal and partially immunosuppressed anti-lymphocyte-globulin (ALGPtreated W y S n mice. The ALG treatment facilitated an earlier appearance of gp7O-positive "sarcoma" cells accompanied by an intense inflammatory response. Time course pulse-labelling studies showed that a decreasing proportion of gp7O-positive "sarcoma" cells were incorporating ['HI-thymidine in vivo in both normal and immunosuppressed mice as the lesion progressed to maximum size. ALG-treated mice inoculated with MSV were given a single injection of ['HI-thymidine immediately prior t o extensive appearance of gp7O-positive "sarcoma" cells (day 6) and were studied for the presence of labelled gp7O-positive cells 2 h, 2 days and 6 days post labelling. The data indicate that few cells divided during the time in which an 8-to 10-fold increase in virus-positive "sarcoma" cell number occurred. These experiments provide evidence that recruitment rather than proliferation of virus-positive cells occurred. The results also suggest that, within the tumor, defense mechanisms develop which restrict sarcomacell proliferation also in ALG-treated mice. The composition of inflammatory cells during the course of tumor progression and regression in the uncompromised mice revealed that the proportion of lymphocytes was highest early and late during tumor development, dropping to a minimum at the peak size of the tumor.Macrophages and granulocytes constituted 70-80 YO of the total cells recovered at peak tumor size and the onset of regression. In the ALG-treated mice, the proportions of macrophages, granulocytes, and infrequent lymphocytes remained constant throughout the duration of the tumor progression. A decrease in total cells, including a decrease in gp7O-positive cells, was noticed before a change in the proportion of infiltrating lymphocytes occurred due to recovery of the immune system. The composition of the inflammatory cells at onset of regression suggests that macrophages and granulocytes are of major importance in the defense against MSV infection.
Courses of tumors, which had been induced in adult STU mice with a regressor and with a progressor strain of Moloney sarcoma virus (MSV-M) were followed and compared. All 73 tumors induced by the regressor strain of MSV-M (R-MSV-M) regressed and 181 of 183 tumors induced by a progressor strain (P-MSV-M) grew progressively and killed their hosts between 16 and 171 days after infection. Even after inoculation of about 4 FFU of P-MSV-M tumor development may occur and lead to progressively growing tumors. Both strains of MSV-M induce strong immune responses in their host, namely cytotoxic effector cells, cytotoxic antibodies and tumor resistance. Simultaneous injection of mice on separate sites with P-MSV-M on one side and R-MSV-M producing ascitic cells on the other side did not induce mutual influences on the different tumor courses. It is therefore concluded that the immune response is obviously not decisive for the failure of P-MSV-M induced tumors to regress. From seven P-MSV-M induced primary tumors two producer and five nonproducer transformants could be isolated, maintained in culture and partly held as easily transplantable tumors in adult immunocompetent mice. Both producer transformants release sarcoma virus with the capacity to induce progressively growing tumors in adult mice. All transformants induce progressively growing tumors after transplantation independent of the applied cell dose. It is concluded that the ability of the P-MSV-M to induce stably transformed cells (in contrast to R-MSV-M, WEILAND et al., Brit. J. Cancer, 1979) favours clonal development and ultimately progressive tumor course, in spite of the presence of an immune response.
SmnmaryCell lines derived as producers and nonproducers from progressor Moloney sarcoma virus induced tumors showed differences in the rescuability of the viral sarcoma genome and in biological activities of released virus. Restoration of transformation defective variants is demonstrated.Recently we reported (8) that infection of mice either with the regressor (R) strain of the Moloney sarcoma-helper virus complex (MSV-M) or with the progressor (P) strain of MVS-M resulted in an effective immune response. However, in spite of this immune reaction, tumors induced by the P strain usually grew progressively in contrast to the regressive growth of R strain induced tumors. I t was shown that both MSV-M strains differ in their capacity to transform cells stably. We always failed to establish stably transformed cell lines from primary R-?cISV-N induced tumors (10) whereas stable transformants could be derived from tumors caused by P-MSV-)/[ (8). From seven P-MSV-M tumor derivatives, two were found to be producers of ecotropic C type virus and five to be nonproducers. The present communication deals with the comparison of oneogenieity and focus forming capacity of C type virus released from the two producer and the five nonprodueer cell lines; the latter after infection with Moloney helper virus (NLV-M) obtained from cells continuously producing MLV-lV[ (7). I t is demonstrated that P-MSV-M infection leads to oneogenic transformants which differ in their rescuability of the P-5fSV-~[ genome, and it describes transformation defective MSV-M variants until now unknown to occur in MSV-M (3).
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