Detection of disseminated tumour cells in blood and bone marrow samples of patients undergoing hepatic resection for metastasis of colorectal cancer.

BACKGROUND: In 50-60 per cent of patients who undergo hepatic resection for metastasis of colorectal cancer the first site of tumour recurrence is extrahepatic, indicating the presence of more extensive disease at the time of resection. The aim of this study was to evaluate whether the presence of disseminated tumour cells in blood and bone marrow could predict extrahepatic tumour recurrence. METHODS: Cytokeratin 20 (CK20) reverse transcriptase-polymerase chain reaction was used to study the presence of tumour cells in preoperative peripheral blood and bone marrow samples from 41 patients with liver metastasis scheduled for surgical resection. RESULTS: CK20 expression was detected in six of 41 peripheral blood samples and in eight of 32 bone marrow samples. There was no correlation between CK20-positive samples and subsequent extrahepatic recurrence. Positive blood samples did, however, correlate with high serum carcinoembryonic antigen level and large tumour volume. None of the 14 patients previously treated with chemotherapy had CK20-positive samples, whereas six of 27 blood and eight of 20 bone marrow samples were positive in the chemotherapy-naive group. CONCLUSION: Although the number of patients in this study is limited, the presence of disseminated tumour cells did not predict subsequent extrahepatic recurrence. The results strongly suggest that the presence of circulating tumour cells in peripheral blood may reflect transient shedding of tumour cells related to large tumour volume.

Investigations for a multi-marker RT-PCR to improve sensitivity of disseminated tumor cell detection.

BACKGROUND: In order to develop a multi-marker RT-PCR, which as such may be more sensitive than a single marker assay for the detection of disseminated tumor cells, we evaluated six RT-PCR markers: cytokeratin 20 (CK20), carcinoembryonic antigen (CEA), guanylyl cyclase C (GCC), epidermal growth factor receptor (EGFR), matrilysin (MMP-7) and HeLa metastatic gene (HLM). MATERIALS AND METHODS: The expression was studied in human colon tumor cell lines, in colon cancer tissues, and in blood and/or bone marrow samples of colorectal cancer patients and control subjects. RESULTS: The cell lines showed a differential expression pattern. The expression of all markers was detected in control blood samples with the lowest frequency for CK20 and EGFR. Semiquantitative analysis, which was performed to study threshold setting, demonstrated that GCC expression was elevated in patient compared to control samples. However, the reproducibility was questionable. CONCLUSION: The results presented in this study suggest an enhanced sensitivity for a combination of RT-PCR markers. Due to limited specificity however, the development of a multi-marker RT-PCR by using conventional PCR does not seem feasible. Future studies should focus on the potential of quantitative RT-PCR.

Limitations of cytokeratin 20 RT-PCR to detect disseminated tumour cells in blood and bone marrow of patients with colorectal cancer: expression in controls and downregulation in tumour tissue.

AIMS: Despite informative staging of patients with colorectal cancer, some patients with localised disease at diagnosis will develop recurrence or metastasis. Attempts to improve staging include sensitive detection of disseminated tumour cells in blood and bone marrow by reverse transcriptase polymerase chain reaction (RT-PCR). The results of this study have been considered in relation to the controversial results in the literature to elucidate the usefulness of cytokeratin 20 (CK20) RT-PCR to detect disseminated tumour cells further. PATIENTS/METHODS: Blood and bone marrow samples from 30 patients with colorectal cancer were studied by CK20 RT-PCR. Specificity was evaluated in 47 blood and 15 bone marrow samples from non-cancer controls. In addition, the expression of CK20 mRNA and protein was studied in normal and tumour colon tissue samples. RESULTS: CK20 expression was detected in nine of 30 and nine of 19 of the blood and bone marrow samples from patients with colorectal cancer, respectively. In non-cancer control blood and bone marrow samples, CK20 expression was detected in 10 of 47 and four of 15, respectively. A difference between patient and control samples may be observed in terms of frequency of positive PCR tests. In tissue samples, CK20 mRNA expression was downregulated in tumour compared with normal colon tissue. CONCLUSIONS: CK20 expression was downregulated in tumour tissue compared with normal colon and a background expression of CK20 was seen in some control blood and bone marrow samples. Despite a lack of standardisation (which hampers comparison of studies), these results, together with other reports in the literature, suggest that CK20 may still be a suitable marker, but that background expression and threshold setting should be studied further.

Matrix metalloproteinases in human melanoma cell lines and xenografts: increased expression of activated matrix metalloproteinase-2 (MMP-2) correlates with melanoma progression.

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) are involved in tumour progression and metastasis. In this study, we investigated the in vitro and in vivo expression patterns of MMP-1, MMP-2, MMP-3, MMP-9, TIMP-1 and TIMP-2 mRNA and protein in a previously described human melanoma xenograft model. This model consists of eight human melanoma cell lines with different metastatic behaviour after subcutaneous (s.c.) injection into nude mice. MMP-1 mRNA was detectable in all cell lines by reverse transcription polymerase chain reaction (RT-PCR), but the expression was too low to be detected by Northern blot analysis. No MMP-1 protein could be found using Western blotting. MMP-2 mRNA and protein were present in all cell lines, with the highest expression of both latent and active MMP-2 in the highest metastatic cell lines MV3 and BLM. MMP-3 mRNA was expressed in MV3 and BLM, and in the non-metastatic cell line 530, whereas MMP-3 protein was detectable only in MV3 and BLM. None of the melanoma cell lines expressed MMP-9. TIMP-1 and TIMP-2 mRNA and protein, finally, were present in all cell lines. A correlation between TIMP expression level and metastatic capacity of cell lines, however, was lacking. MMP and TIMP mRNA and protein expression levels were also studied in s.c. xenograft lesions derived from a selection of these cell lines. RT-PCR analysis revealed that MMP-1 mRNA was present in MV3 and BLM xenografts, and to a lesser extent in 530. Positive staining for MMP-1 protein was found in xenograft lesions derived from both low and high metastatic cell lines, indicating an in vivo up-regulation of MMP-1. MMP-2 mRNA was detectable only in xenografts derived from the highly metastatic cell lines 1F6m, MV3 and BLM. In agreement with the in vitro results, the highest levels of both latent and activated MMP-2 protein were observed in MV3 and BLM xenografts. With the exception of MMP-9 mRNA expression in 530 xenografts, MMP-3, MMP-9, and TIMP-1 mRNA and protein were not detectable in any xenograft, indicating a down-regulated expression of MMP-3 and TIMP-1 in vivo. TIMP-2 mRNA and protein were present in all xenografts; interestingly, the strongest immunoreactivity of tumour cells was found at the border of necrotic areas. Our study demonstrates that of all tested components of the matrix metalloproteinase system, only expression of activated MMP-2 correlates with increased malignancy in our melanoma xenograft model, corroborating an important role of MMP-2 in human melanoma invasion and metastasis.

TM7XN1, a novel human EGF-TM7-like cDNA, detected with mRNA differential display using human melanoma cell lines with different metastatic potential.

We have identified a novel 3845 bp cDNA differentially expressed in a human melanoma metastasis model. Northern blot analysis showed expression in the poorly and intermediately metastasizing cell lines and a marked downregulation in the highly metastatic cell lines. Using RT-PCR expression was also seen in several other tumor cell lines and normal cell types of human origin. cDNA sequence analysis revealed an ORF of 687 amino acids containing seven putative transmembrane domains C-terminally and a long N-terminus. The gene was mapped to 16q13. Highest homology was observed with members of the EGF-TM7 subfamily of the secretin/calcitonin receptor family. We propose the delineation of a subfamily of TM7 proteins, LN-TM7, containing seven transmembrane proteins with a long N-terminal extracellular part.

CTp11, a novel member of the family of human cancer/testis antigens.

To identify new genes that may contribute to the metastatic pathway of neoplastic cells, we compared mRNA expression of the parental human melanoma cell line 1F6 and its metastatic variant 1F6m using mRNA differential display. We isolated a cDNA clone that was exclusively expressed in 1F6m. Northern blot analysis on a broader panel of human melanoma cell lines with different metastatic capacity following s.c. inoculation into nude mice demonstrated that the gene was expressed only in the most aggressive, highly metastatic cell lines, giving a band of 0.5 kb. The isolated full length cDNA clone showed an open reading frame of 97 amino acids. To study the subcellular localization of the gene product, COS-1 cells were transfected with cDNA of the gene fused to eGFP. We found the fusion protein to be exclusively present in the nucleus. A computer search showed strong homology with human genomic clones all localized on chromosome X (Xq26.3-Xq27.1) and with several expressed sequence tags, all from testis. Localization of the gene on chromosome X was confirmed by genomic PCR on a panel of human chromosome-specific rodent/human hybrid cell lines. Northern blotting and reverse transcription-PCR on 17 different normal human tissue samples showed that the gene was only expressed in normal testis. Reverse transcription-PCR on a great number of different human tumor cell lines showed expression in 25-30% of the melanoma and bladder carcinoma cell lines. Only 2 of 29 other tumor cell lines were positive. Nested PCR analysis of a series of fresh human melanocytic tumors demonstrated expression in 7 of 10 melanomas tested. No expression was seen in benign melanocytic tumors. In addition to melanoma, some malignant tumors from other histological types were also found to be positive. Based on these data, we conclude that the described gene, CTp11 (cancer/testis-associated protein of 11 kDa), is a novel member of the family of cancer/testis antigens.

The disintegrin eristostatin interferes with integrin alpha 4 beta 1 function and with experimental metastasis of human melanoma cells.

Peptides containing the integrin recognition sequence, RGD, can inhibit experimental metastasis of mouse melanoma cells, but the integrin(s) affected in these experiments is unknown. Besides "classical" RGD-binding integrins such as alpha 5 beta 1 and alpha v beta 3, RGD has been reported to bind alpha 4 beta 1, and mAbs to alpha 4 beta 1 can inhibit melanoma metastasis. We investigated the mode of action of the disintegrin eristostatin, an RGD-containing peptide isolated from snake venom, in a human melanoma experimental metastasis model. Lung colonization following i.v. injection of MV3 cells in nude mice was strongly inhibited by eristostatin. MV3 cells bound FITC-eristostatin and adhered to eristostatin-coated wells. This adhesion was partially inhibited by a GRGDSP peptide and by alpha 4 mAb. Binding of FITC-eristostatin to Jurkat cells and adhesion of Jurkat (but not K562) cells to eristostatin-coated wells further suggested that eristostatin binds alpha 4 beta 1, even though, again, alpha 4 mAb only partially inhibited adhesion. Expression of alpha 4 beta 1 was enhanced in metastatic melanoma cells compared to normal melanocytes and nonmetastatic melanoma cells. Finally, eristostatin inhibited adhesion of both MV3 and CHO alpha 4 cells to the alpha 4 beta 1-ligand VCAM-1, while adhesion to other ligands via other integrins was not affected. These findings demonstrate that inhibition of melanoma cell metastasis by RGD-containing peptides such as eristostatin, may be due to interference with alpha 4 beta 1-VCAM binding, in addition to inhibition of the classical RGD-binding integrins.

Vascular density in melanoma xenografts correlates with vascular permeability factor expression but not with metastatic potential.

We studied the relation between tumour vascular density and tumour growth rate, metastatic incidence and vascular permeability factor (VPF) mRNA levels in a human xenograft model described previously. Vascular density was determined by automated image analysis. Xenografts derived from cell lines BLM and MV3 showed the highest mean vascular density (MVD), the highest in vivo growth rate, high VPF mRNA levels and rapid development of lung metastases. Xenografts of cell lines M14, Mel57 and MV1 showed a significantly lower degree of vascularization, lower in vivo growth rates and lower levels of VPF mRNA, but formed lung metastases with a similar incidence as those of BLM and MV3. Xenografts from cell line 1F6 did not form lung metastases, whereas tumours derived from a spontaneous mutant of 1F6, designated 1F6m, gave rise to lung metastases to the same extent as Mel57, M14 and MV1 tumours. MVD values in 1F6 and 1F6m xenografts, VPF mRNA levels and in vivo growth rates of 1F6 and 1 F6m xenografts, however, were similar. In conclusion, in the melanoma xenograft model vascular density is correlated with in vivo growth rate and with in vitro VPF mRNA levels, but not with the ability to metastasize.

Integrin beta 3 cDNA transfection into a highly metastatic alpha v beta 3-negative human melanoma cell line inhibits invasion and experimental metastasis.

Even though integrin alpha v beta 3 is thought to play a role in invasive growth of melanomas, some metastatic melanoma cell lines lack alpha v beta 3, and downmodulation of alpha v beta 3, expression can enhance the invasive capacity of certain melanoma cells. To further investigate this apparent dualistic role of alpha v beta 3, we transfected beta 3 cDNA into the highly metastatic, beta 3-negative human melanoma cell line MV3. MV3 cells adhered to fibronectin but not to fibrinogen or a synthetic RGD peptide, while MV3-beta 3 adhered to all three RGD-containing adhesive ligands, and this adhesion was inhibited by LM609 alpha v beta 3 mAb. Expression of alpha v beta 3 did not affect MV3 in vitro proliferation or in vivo tumorigenicity upon subcutaneous inoculation into nude mice. In contrast, it strongly reduced invasion in matrigel and lung colonization in nude mice of MV3 cells. Thus, certain melanoma cell lines have adopted a metastatic strategy in the absence of alpha v beta 3, and in such cells expression of this integrin leads to a less aggressive phenotype.

Simultaneous suppression of progression marker genes in the highly malignant human melanoma cell line BLM after transfection with the adenovirus-5 E1A gene.

The highly metastatic human melanoma cell line BLM was transfected with the E1A or E1A + E1B regions of adenovirus 5 (Ad5). A series of progression markers, correlated with the malignant phenotype of parental BLM (including calcyclin, thymosin beta 10, plasminogen activator inhibitors types 1 and 2, urokinase type and tissue type plasminogen activators, vimentin, tissue type transglutaminase, and interleukin-6), was collectively repressed in the transfectants, whereas several control genes were not affected or even induced. The apparently coordinate repression of a set of markers by the same regulator gene, Ad5 E1A in this case, suggests the existence of one pathway under the control of a main switch and predicts that one or more as yet unidentified cellular master genes normally exert this function. A reduced oncogenicity was observed after subcutaneous inoculation of the E1A transfectants into nude mice and provides additional evidence in support of a tumor suppressor function of Ad5 E1A.

The role of monoclonal antibody affinity in tumor immunotherapy evaluated in in vivo models for minimal residual disease.

To evaluate the role of affinity in monoclonal antibody (mAb)-mediated treatment of carcinomas, we compared the antibodies 17-1A and 323/A3 that bind with different affinities overlapping epitopes on the epithelial adhesion molecule Ep-CAM. This comparison was performed in several models for minimal residual disease in mice grafted with Ep-CAM transfected B16 melanoma cells originating from C57BL/6 mice. These cells were either grafted subcutaneously or injected intravenously into nude BALB/c mice, or grafted subcutaneously in immunocompetent C57BL/6 mice. In the BALB/c subcutaneous model, significant therapeutic results (p < 0.05) compared with the control mAb were obtained with both mAbs 17-1A and 323/A3. However, when treating lung metastases in nude BALB/c mice that had developed after intravenous injection of the B16/Ep-CAM tumor cells, only the high-affinity 323/A3 mAb could significantly (p < 0.05) reduce the number of metastases that appeared. In syngeneic C57BL/6 mice grafted subcutaneously with B16/ Ep-CAM cells, a single 323/A3 or 17-1A mAb injection had no effect, in contrast to that observed for the nude BALB/c mouse model. However, multiple injections of the 323/A3 mAb significantly (p < 0.005) reduced the mean tumor volume, although they did not prevent tumor development. The results show that in vivo antibody-mediated effector cell activation and subsequent tumor cell elimination is determined by mAb affinity and target antigen density. Therefore, treatment of minimal residual disease with high-affinity mAb 323/ A3 is expected to improve the clinical results obtained with mAb 17-1A.

Expression of nma, a novel gene, inversely correlates with the metastatic potential of human melanoma cell lines and xenografts.

nma, a novel gene, was isolated by using a subtractive hybridization technique in which the gene expression was compared in a panel of human melanoma cell lines with different metastatic potential. nma mRNA expression (1.5 kb) is high in poorly metastatic human melanoma cell lines and xenografts and completely absent in highly metastatic human melanoma cell lines. Fluorescence in situ hybridization combined with the analysis of a panel of human-rodent somatic cell hybrids indicated that the nma gene is located on human chromosome 10, in the region p11.2-p12.3. Sequence analysis of nma showed no homologies with other known genes or proteins, except for several partially sequenced cDNAs. The predicted amino acid sequence suggests that the protein encoded by nma contains a transmembrane domain. Expression of nma is high in human kidney medulla, placenta and spleen, low in kidney cortex, liver, prostate and gut and absent in lung and muscle. Whereas nma is not expressed in normal skin tissue, expression is high in melanocytes and in 3 out of 11 melanoma metastases tested.

Alpha v-integrins in human melanoma: gain of alpha v beta 3 and loss of alpha v beta 5 are related to tumor progression in situ but not to metastatic capacity of cell lines in nude mice.

We investigated the expression of alpha v-integrins in different stages of human cutaneous melanocytic tumor progression. We observed that alpha v beta 5 was the alpha v-integrin expressed in all common nevocellular nevi, in 78% of dysplastic nevi, in 63% of early primary melanomas, in 43% of advanced primary melanomas, and in 33% of melanoma metastases. Hence, loss of alpha v beta 5 expression was related to melanocytic tumor progression. In line with earlier reports, alpha v beta 3 was exclusively detected in advanced primary melanomas and metastases (24% and 50% respectively). Staining with anti-alpha v monoclonal antibodies (MAbs) in lesions where both alpha v beta 3 and alpha v beta 5 were absent showed that alternative alpha v-integrins were expressed in advanced primary melanomas and metastases. By FACS analysis, we determined expression of alpha v beta 5 and alpha v beta 3 in 4 human melanoma cell lines with different metastatic capacities after s.c. inoculation into nude mice. One of the non-metastatic and both highly metastatic cell lines expressed alpha v beta 5 at their surface. Surprisingly, alpha v beta 3 was detected exclusively in the non-metastatic cell lines. Absence of alpha v beta 3 in the highly metastatic cell lines was confirmed by lack of immunoprecipitation from 35S-methionine-labeled cells and by absence of immunohistochemical staining on primary and metastatic xenograft lesions. Our findings indicate that alpha v beta 5 expression is often lost in advanced stages of melanocytic tumor progression in situ, while alpha v beta 3 is acquired, but that a decrease in alpha v beta 5 and an increase in alpha v beta 3 expression are not necessarily related to the metastatic behavior of human melanoma cells in nude mice.

Establishment and characterization of a human melanoma cell line (MV3) which is highly metastatic in nude mice.

To select human melanoma cells that are highly tumorigenic and metastatic in nude mice we have implanted fragments of a fresh human melanoma metastasis subcutaneously (s.c.) into a nude mouse. After 3 passages in nude mice, part of the xenograft was cultured and a new melanoma cell line, MV3, was established. After intravenous (i.v.) inoculation of 2 x 10(6) MV3 cells, 95% of the nude mice (n = 20) developed lung colonies within 6 weeks. S.c. inoculation of 2 x 10(6) MV3 cells resulted in 95% tumor take, while 90% of the mice (n = 20) showed spontaneous metastases in the lungs within 7 weeks. Histological and immunohistological features of the original tumor of the patient were largely retained in the tumors of the mice and in the cell line in vitro. As shown by Alcian blue staining, MV3 cells contain large quantities of glycosaminoglycans (GAGs) and/or proteoglycanes (PGs), both in vivo and in vitro. The cells showed a marked expression of transferrin receptor, ICAM-1, EGF-receptor, and VLA-2 integrin. As only few human melanoma cell lines are available that frequently show metastasis in nude mice, the highly metastatic MV3 cell line represents a useful tool for studying the expression and regulation of molecules on human melanoma cells involved in the process of metastasis.

Progression markers in metastasizing human melanoma cells xenografted to nude mice (review).

The past decade transplants of human tumors in nude mice have been increasingly used as an experimental model for local tumor growth and dissemination. A few human melanoma cell lines have been described that give rise to metastases in nude mice after subcutaneous inoculation. First we give an overview of some relevant literature with respect to the pathogenesis of tumor metastasis, models to study human cancer metastasis, neoplastic progression and the detection of antigens involved in metastasis. Finally we describe our results concerning the morphological and immunohistochemical profile of six different human melanoma cell lines and their xenograft lesions in nude mice using a set of monoclonal antibodies recognizing different categories of human melanoma-associated antigens. From the data we conclude that the nude mouse mouse model appears suitable to study the role of melanoma-associated progression markers in the pathogenesis of metastasis.

Expression of donor class I major histocompatibility antigens on the vascular endothelium of mouse skin allografts.

The expression of a class I MHC antigen on the vascular endothelium of mouse skin allografts was assessed by in vivo uptake of radiolabeled monoclonal anti-class-I antibody in the grafts after i.v. injection into the recipients. Endothelial localization of the bound antibodies was demonstrated via double-labeling immunofluorescence microscopy using factor-VIII-related antigen as a marker for endothelial cells. Treatment of recipients with cyclosporine was accompanied by low levels of class I antigen expression in the grafts, and similarly low levels were measured in grafts carried by nude recipients in the complete absence of rejection. Withdrawal of immunosuppressive therapy was followed by an increased class I antigen expression in the donor skin. An increase was also observed in skin grafts undergoing first-set rejection. We conclude that the expression of class I antigens on the capillary endothelium of mouse skin allografts in vivo is variable and is under influence of the immune status of the recipient.

A comparative study of total body irradiation as a method of inducing granulocyte depletion in mice.

Since conventional methods of inducing depletion of polymorphonuclear granulocytes (PMNs) in mice, such as treatment with cytostatic drugs and anti-PMN sera, proved to be insufficient to induce a stable PMN depletion for several days, and were accompanied by considerable toxic side effects, we induced neutrophil depletion in mice by total body irradiation (TBI) in a single dose of 6.0 Gy (600 rads.) at a dose rate of 0.20 Gy/min. This treatment reduced the number of PMNs in the peripheral circulation to values below 150/microliter from day 3-10 after irradiation. The number of lymphocytes fell simultaneously. Platelet counts remained above 60% of normal values during the first 7 days after irradiation. Complement levels were not significantly affected by TBI. The results show that TBI of 6.0 Gy induces pronounced and stable PMN depletion in mice for at least 7 days. Furthermore, under an aseptic regimen the mice can be kept in good condition and losses are less than 5%.

Acute antibody-mediated rejection of skin grafts without involvement of granulocytes or complement.

In immunosuppressed mice that carry rat skin xeno-grafts, acute antibody-mediated graft rejection (AAR) can be induced by intravenous administration of mouse anti-rat globulin. Dependent on the amount of antibody injected and on the complement status of the recipient, an Arthus-like or a Shwartzman-like pattern of vasculitis occurs. The role of polymorphonuclear granulocytes (PMNs) in either type of vasculitis was tested by inducing AAR in recipients depleted of PMNs by total body irradiation. Despite the absence of PMNs in the graft vessels, AAR occurred both in the Arthus-like and in the Shwartzman-like type. Moreover, AAR could be elicited in PMN-depleted recipients that were complement-depleted by cobra venom factor treatment or were congenitally C5-deficient. We conclude that neither the PMN nor complement is an essential mediator the PMN nor complement is an essential mediator in this form of antibody-mediated vasculitis.

Absence of requirement for polymorphonuclear granulocytes in the acute antibody-mediated rejection of murine skin allografts.

The role of polymorphonuclear granulocytes (PMN) in acute antibody-mediated rejection (AAR) was studied in a murine skin allograft model. B10.A skin was grafted onto B10.D2 recipients that were treated with goat antimouse lymphocyte serum, to postpone cellular rejection. This prolonged the median survival time of the grafts to 21.5 +/- 1.0 days. PMN depletion was effected by total body irradiation of 6.0 Gy (600 rads) on day 4 after grafting, which reduced the number of PMN in the circulation to levels below 150/microliters from days 3-10 after the irradiation. To induce AAR the mice received, on day 8 after grafting, an i.v. injection of a monoclonal antibody with specificity against the donor H-2Kk antigen together with 0.25 ml fresh rabbit serum. This caused acute rejection of all grafts in the control group within 72 hr, with abundant presence of PMN in the graft vessels on histologic examination. In PMN-depleted recipients the reaction in the grafts was somewhat retarded in th first 24 hr, but nevertheless acute rejection occurred within 72 hr in 9 of 11 animals, whereas PMN were virtually absent from the grafts. The results show that PMN act as accelerators and amplifiers of the acute antibody-mediated rejection process, but are not essential mediators in the damage to the vascular endothelium of the grafts.

The role of complement in the induction of acute antibody-mediated vasculitis of rat skin grafts in the mouse.

Rat skin grafts carried by immunosuppressed mice can be acutely destroyed by intravenous administration of mouse anti-rat antibody. The velocity of the reaction and the histologic sequence of events depend on the amount of antibody administered: low doses give an Arthus-like rejection, whereas at high doses a Shwartzman-like pattern occurs. Depletion of C3 by cobra venom factor treatment did not prevent acute rejection after intravenous injection of high doses of antiserum but changed the reaction from a Shwartzman-like to an Arthus-like pattern. Conversely, supplementary administration of rabbit complement caused a violent Shwartzman-like graft destruction after injection of low doses of antibody, which in complement-normal mice gave an Arthus-like reaction. The results show that complement can greatly amplify the antibody-mediated immune vasculitis and can substantially modify its histologic pattern. It is, however, not an absolute requirement for the occurrence of the destructive process.