The fetus as an allograft: evidence for antiidiotypic antibodies induced by pregnancy

We tested sera from 20 women [9 parous, 8 with no children, and 3 with abortion(s)] for inhibition in mixed lymphocyte culture (MLC). In these experiments, the responder (wife) lymphocytes were treated with autologous serum and rabbit complement and then tested for responses against stimulator cells from the husband and from third-party allogeneic donors. The results demonstrate that antibodies capable of inhibiting responses of wife's lymphocytes to husband's cells in MLC are present in sera from parous women, but not in women without children and in women with abortion(s). The MLC-inhibiting activity in parous women sera was in the IgG fraction. The results from immunofluorescence and absorption experiments suggest that the inhibition in MLC was due to antibodies directed against recognition sites on wife's T lymphocytes against husband's alloantigens. These observations suggest that antiidiotypic antibodies against husband-specific idiotypes on wife's lymphocytes could be induced by pregnancy and that maternal tolerance to fetus may be attributable to a similar mechanism occurring in vivo.

Purification of melanoma-associated oncofetal antigen gp87 from spent medium and cell homogenate of cultured human melanoma cells

A melanoma-associated glycoprotein with an apparent molecular weight of 87,000 daltons (gp87) defined by the monoclonal antibody 140.240 has been purified from the spent medium and from cell homogenates of cultured human melanoma cells through a three-step purification procedure. The procedure involves a DEAE-Sephadex A-25 ion-exchange column, SephacrylS-200 gel filtration and antibody-Sepharose-4B-affinity chromatography. By this approach we achieved a 1205-fold increase in specific activity with a 42% antigen recovery from spent medium concentrate, and a 3366-fold increase in specific activity with a 29% antigen recovery from the cell homogenate. The antigen was purified from these two sources of starting material with a high degree of purity as visualized in a single protein band in SDS-polyacrylamide gel electrophoresis. Thus these procedures described offer an efficient approach to the purification of gp87 molecules for further biochemical studies.

Enhanced natural killer sensitivity with concomitant clonal selection for cells bearing homogeneously staining regions in the human melanoma cell line MeWo upon induction of differentiation with theophylline

Culture of the human melanoma cell line MeWo in the presence of 1 mM theophylline was associated with an increase in susceptibility to natural killer (NK)-mediated cytolysis. The phenomenon was detected as early as 72 hours after initiation of theophylline treatment, reaching maximum values at 3-4 weeks and remaining stable for longer than 3 months of testing, provided the cells were maintained in the presence of theophylline. The alteration in target sensitivity was selective for NK-mediated cytolysis, since other mechanisms of cell-mediated cytolysis, including antibody-dependent cell-mediated cytotoxicity and monocyte-mediated and lectin-induced cytolysis, were comparable between untreated and treated cells. The enhanced susceptibility of theophylline-treated cultures to NK lysis, as compared to NK lysis susceptibility of untreated MeWo cells, was not significantly changed by pretreatment of effector lymphocytes with interferon. Evidence for differentiation in theophylline-treated cultures was obtained. In addition, however, cytofluorometric and karyologic analysis revealed the existence of two subpopulations of differing ploidy in the MeWo line. The hypodiploid, NK-sensitive subpopulation, bearing homogeneously staining regions on two chromosomes, could be selected by growth in theophylline. Therefore, selection of subpopulations in heterogeneous tumor cell lines by chemical inducers suggests an alternative and novel mechanism for enhancement of NK sensitivity.

Sensitivity of human carcinoma cell lines to lysis by blood natural killer cells correlating with surface expression of carcinoembryonic antigen

The HCT-8R clone of the HCT-8 human colon tumor line, which expresses increased quantities of carcinoembryonic antigen (CEA) on its surface, was discovered to have an enhanced susceptibility to lysis by natural killer (NK) cells in human peripheral blood. This increase in susceptibility to lysis by peripheral blood mononuclear cells was not explained by stimulation of interferon release by HCT-8R cells but rather was found to be attributable to an increased susceptibility of HCT-8R cells to lysis by those NK cells that bind to sheep erythrocytes (E-RFC). Cold target competition experiments and single-cell assay for cytotoxic cells suggested that the presence of surface CEA did not increase lysis of HCT-8R by facilitating "recognition" by E-RFC-type cytotoxic cells but by rendering HCT-8R cells more susceptible to the lytic mechanism of NK cells. The magnitude of expression of surface CEA by a variety of human carcinoma cell lines with a few exceptions and subclones of HCT-8 also correlated with increased susceptibility to lysis by blood mononuclear cells. The possible clinical significance of these findings was discussed.

Selective extraction by 1-butanol of surface glycoprotein antigens from human melanoma cells

The butanol extraction method has previously been used to achieve selective release of tumor-specific transplantation antigens from mouse sarcoma cells. In this study we investigated the feasibility of this method for extracting four surface glycoprotein antigens (87K, 95-150K, HLA-DR, and HLA-A,B,C) from cultured human melanoma cells. Of the four antigens examined, only 95-150K and HLA-DR antigens could readily be detected in material extracted by 2%, 3%, or 5% butanol. The 3% butanol was found to be most effective in releasing these two antigens. Treatment of melanoma cells with less than or equal to 3% butanol did not decrease the viability of extracted cells as judged by either Trypan Blue dye exclusion or plating efficiency. Thus the noncytolytic butanol extraction method offers a promising approach to the isolation of certain glycoproteins such as 95-150K and HLA-DR from viable human melanoma cells for further purification and structural analysis.

Two-step enrichment of HLA-DR antigens from spent medium of human malignant melanoma culture by flotation and density separation procedures

HLA-DR antigens released by cultured human melanoma cells were harvested from spent medium. Antigenic activity was monitored by quantitative absorption analysis in the mixed hemadsorption assay using anti-HLA-DR rabbit antiserum. Following concentration by amicon filtration, and removal of insoluble components by centrifugation at 136,000 g, the spent medium was subjected to KBr (density, 1.23 g/ml) flotation. The antigenic material was enriched in the upper one-third fraction (lipoprotein-rich), by a factor of 7 with 79% recovery. Further purification of this upper fraction by sucrose (5-30%) density gradient resulted in a marked increase in antigenic activity in the bottom fraction (No. 6), by a factor of 167 with 56% recovery from the spent medium concentrate. Thus, these procedures offer a promising approach towards the isolation of HLA-DR antigens from shed material of cultured melanoma cells for further purification and structural studies.

Human melanoma-specific oncofetal antigen defined by a mouse monoclonal antibody

140.240, an IgG2a mouse monoclonal antibody raised against a cultured human melanoma cell line, was highly specific for melanoma cells as determined by direct and absorption analyses in a mixed hemadsorption assay. Supernatants of doubly cloned hybridomas producing antibody 140.240 reacted with all cultured and fresh melanomas tested but failed to react with a variety of carcinomas, sarcomas, lymphomas, leukemias and other tumors of neuroectodermal origin. This antibody did not react with B-lymphoid cell lines, ruling out HLA-DR specificity. Non-reactivity of antibody 140.240 with peripheral blood lymphocytes obtained from the donor of the immunizing melanoma line excluded the possibility of detecting histocompatibility antigens. Nevus cells were also non-reactive. However, antibody 140.240 did identify an antigenic determinant on tissue homogenates prepared from fetuses of 10-14 weeks' gestation. The antigen involved was shed by cultured melanoma lines and, by immunoprecipitation analysis of radiolabelled lysates, had a molecular weight of approximately 87kdal. Thus, the structure identified by monoclonal antibody 140.240 is a melanoma-specific oncofetal antigen.

Changes in HLA-DR antigen expression on cultured human melanoma cells during theophylline treatment

Two human malignant melanoma cell lines, differing in their patterns of HLA-DR antigen expression, were examined for changes in antigen expression following theophylline treatment. In one line, the basal HLA-DR antigen content of which remained constant during culture, theophylline decreased HLA-DR expression, accompanied by morphological changes indicating increased differentiation. In the second line, the surface HLA-DR antigen expression decreased with time during culture and showed no decrease in antigen expression or morphological changes when cultured in the presence of theophylline.

Absence of melanoma specificity in the reactivity of melanoma patients' sera with cultured allogeneic melanoma cell lines

While patients with melanoma are known to produce antibodies against melanoma cells, the tumor specificity of these reactions has not been well documented. Using the sensitive mixed hemadsorption assay we have identified antibody against one or more of nine different cultured melanoma cell lines in only nine of 48 patients with melanoma. Reactivity against melanoma cell lines was seen only in females, 9/27 versus 0/21 males. The strongest melanoma reactivity was seen in sera which also contained lymphocytotoxic antibody. The reactivity was not melanoma specific because it could be removed by absorption either with pooled platelets, nonmelanoma tumor cells or in two cases, by both. We conclude that the occurrence of specific antimelanoma antibodies against common or shared surface melanoma associated antigens is an uncommon event in melanoma patients not receiving specific active immunotherapy. The clinical significance of the observed reactivity and whether it is directed against cancer associated determinants, fetal antigens, or normal tissue or histocompatibility antigens requires further study.

Enhanced expression of melanoma-associated antigens and beta 2-microglobulin on cultured human melanoma cells by interferon

The effect of human leukocyte interferon (IFN) on the in vitro growth and expression of melanoma-associated antigens (MAA). beta 2-microglobulin (beta 2m) and HLA-DR antigen on cultured human melanoma cells was studied. Exposure of melanoma cells to IFN for 64 hours resulted in a dose-dependent inhibition of growth with 46% reduction in cell number at 10(3) U IFN/ml and 74% reduction at 10(5) U/ml. Quantitative absorption experiments in the mixed hemadsorption assay determined that the expression of MAA and beta 2m on treated cells was enhanced at 10(2)-10(5) U IFN/ml, twofold to fivefold for MAA and fivefold to twelvefold for beta 2m. No change was seen in HLA-DR antigen expression. The IFN-induced enhancement of MAA and beta 2m could be detected as early as after 16 hours and a maximum expression was reached at 96 hours after IFN exposure. The IFN-induced enhancement of MAA and beta 2m on melanoma cells was reversible. Studies with melanoma cells grown in stationary phase and serum-deprived conditions indicated that IFN-induced augmentation of MAA and beta 2m did not require cell proliferation. The data suggest that the effect of IFN on antigen expression is independent of its effect on cell growth. Further studies are needed to fully elucidate the mechanism.

Common neuroectodermal antigens on human melanoma, neuroblastoma, retinoblastoma, glioblastoma and fetal brain revealed by hybridoma antibodies raised against melanoma cells

The hybridoma system has been utilized to produce antibodies to characterize the cell surface antigens on human melanoma cells. On initial screening, two antibodies derived by the fusion of mouse myeloma cell (SP2/0-Ag14) and splenocytes from a mouse immunized with a melanoma cell line (CaCL 78-1) showed cross-reactivity with 10 melanoma cell lines and did not react with any of 4 epithelial cancer lines, or 4 normal adult fibroblast lines. However, because of reactivity with 2 neuroblastoma cell lines, additional testing with other neuroectodermal derivatives was carried out and revealed a broad cross-reactivity among melanomas, neuroblastomas, retinoblastomas and glioblastomas and against antigens shared by fetal but not adult brain. Thus, these results indicate the existence of common neuroectodermal antigens on melanoma cells. Before melanoma specificity can be claimed for, an antibody reactivity with nonmelanoma cells bearing these neuroectodermal antigen should be excluded.

Identification of immunoglobulin class and subclass of mouse monoclonal antibodies to human cell surface antigens by mixed hemadsorption assay

A microassay is described to determine immunoglobulin Ig class or IgG subclass of mouse monoclonal antibodies by mixed hemadsorption assay. Monoclonal antibody bound to adherent target cells is reacted with serial dilutions of a panel of class or subclass specific rabbit anti-mouse Ig antisera and binding of the latter is traced by anti-rabbit globulin-coated indicator erythrocytes. The class or subclass of the bound monoclonal antibody is revealed by preferential binding of the corresponding rabbit antibody. Unlike gel immunodiffusion analysis, the mixed hemadsorption assay may be performed with unconcentrated hybridoma culture supernatants.

Fetal erythropoiesis in steel mutant mice. III. Defect in differentiation from BFU-E to CFU-E during early development

Erythroid progenitor cells in +/+ and Sl/Sld fetal livers manifested as burst-forming units-erythroid (BFU-E) and colony-forming units-erythroid (CFU-E) were assayed in vitro during early development. The proportion of BFU-E was higher as mutant than in normal fetal livers. On the other hand, the proportion of CFU-E was less in the mutant than in the normal. These results suggest that the defect in Sl/Sld fetal hepatic erythropoiesis is expressed at the steps of differentiation that effect the transition from BFU-E to CFU-E.

Characterisation of an inhibitor of thymidine uptake produced by cultured human melanoma cells

Supernatants of established cultures of human neoplastic and normal cells have been shown to contain a number of different biological activities, including inhibition of DNA synthesis as measured by thymidine uptake. We have found that supernatants of melanoma cell lines contain an inhibitor of thymidine uptake which is heat labile, ultraviolet sensitive, non-filtrable (0.22 mu) and partially sedimentable at 20,000 x g. The mechanism of action of the inhibitor involves the degradation of 3H-thymidine to a non-utilisable form, which we detect by failure of uptake of 3H-thymidine by cultures of mitogen stimulated lymphocytes to which the inhibitor is added. While microbiological tests have failed to reveal mycoplasma contamination of inhibitor producing cultures, treatment of these cultures with kanamycin suppresses inhibitor production. Qualitative evaluation of DNA synthesis by the inhibitor producing cultures using autoradiography and fluorescent DNA staining has confirmed the presence of mycoplasma. With the widespread use of established cell lines in cancer research, it is imperative that screening for mycoplasma contamination go beyond routine microbiological assays. Detection of 3H-thymidine degradation by cell culture supernatants is an additional simple and sensitive indirect test which could be used for this purpose.

Characterization of human malignant melanoma cell lines. VII. Glycoprotein synthesis and shedding as revealed by [3H]glucosamine labeling

We have established conditions for the study of membrane glycoprotein synthesis and turnover in cultured human malignant melanoma cell lines using the labeled precursor [3H]glucosamine. Uptake of label increased parallel with cell growth, reaching a steady state in resting cultures. Fifteen to 30% of incorporated label can be released from the cells by trypsin treatment depending on the conditions of exposure to the enzyme, and about 50% of the incorporated label is spontaneously shed from the cells within 96 hr of incubation. Labeling in exhausted medium gave a 5- to 8-fold increase in uptake which was inhibited by addition of glucose (2 mg per ml) into the culture medium. The percentage of trypsin-releasable material was identical in fresh and exhausted medium; however, the percentage shed was less in cells initially labeled in exhausted medium. These data provide background information for further studies on the antigenic composition of the glycoproteins of cultured melanoma cells.

Characterization of human malignant melanoma cell lines; V. Heterotransplantation in the hamster cheek pouch

Seven continuous cell lines of human malignant melanoma were studied in terms of their in vivo growth potential in the cheeck pouch of the cortisonized golden hamster. Progressive tumor growth was noted only among the melanoma lines which were grossly pigmented (10/32 transplants). None of the three amelanotic tumor lines showed progressive growth. The growing tumors could be identified as melanoma on morphological grounds and by histochemical demonstration of melanin granules. Histology of the tumor lesions revealed evidence of a host reaction to the tumor transplants. This was confirmed by demonstration of circulating antibodies directed against the implanted human cells. Correlations between in vivo heterotransplantability and in vitro saturation density of human melanoma cells were not found in the present study.

Characterisation of human malignant melanoma cell lines. VI. Inhibition of 3H-thymidine uptake by normal stimulated lymphocytes

Cultured human malignant melanoma cells, when added to normal human lymphocytes stimulated to proliferate by mitogen or antigen, were found to inhibit the uptake of 3H-thymidine (3H-T) by the lymphocytes. A heat-labile factor present in the supernatants of the melanoma cultures is responsible for inhibition. Cell viability and blastogenesis are unimpaired in the lymphocyte cultures containing the inhibitor. Inhibition of 3H-deoxyuridine uptake was also noted indicating that both salvage and de novo pathways of DNA synthesis are involved. Lymphocytes appear to be preferentially affected as cultured colon cancer cells take up 3H-T normally in the presence of the inhibitor. Normal mitotic indices and biochemical estimation of DNA content in lymphocyte cultures containing the inhibitory factor indicate that DNA synthesis does proceed normally. The mechanisms of action of the inhibitor would appear to involve alteration of exogenous nucleoside rather than a metabolic inhibition of intracellular nucleic acid synthesis.

Characterization of human malignant melanoma cell lines. IV. Cytologic and histochemical characteristics

The cytologic and histochemical characteristics of seven established human melanoma cell lines were studied using monolayer culture and cytocentrifuge perparations. The morphology of the cells is different in the two preparations. There is a strong resemblance between the Cytocentrifuge preparations and the histological tissue sections and cytologic smears that are used in routine diagnostic work.

Cellular morphology of human malignant melanoma in primary culture

Early monolayer outgrowths of cells from human cutaneous malignant melanomas mostly derived from metastatic lesions were examined microscopically. Cells resembling the two dendritic types of melanoma previously described in the established lines could readily be recognized. Of 22 specimens, 14 consisted of cells with a triangular dendritic morphology, four had both triangular and elongated dendritic morphology, and one had a cuboidal morphology. The remaining three specimens showed only fibroblastic outgrowths. It is concluded that cells with a triangular dendritic morphology are either the most common type of the secondary cutaneous melanomas, or alternately the most adaptable to the present culture conditions. An association of a more favorable prognosis with the homogeneous triangular dendritic cell type is noted.

Common and individually specific chromosomal characteristics of cultured human melanoma

Since individual chromosomes can be accurately identified by new banding techniques, atebrin fluorescence was used for chromosome analysis in six cell lines and two primary outgrowths derived from human malignant melanoma. Gross aneuploidy was seen in all specimens, but each culture contained at least 1 distinctive marker chromosome specific for that cell line in 87 to 100% of metaphases. One of the primary explants contained a marker that was demonstrable in fresh tissue and persisted through 2 weeks of culture. The same marker was found in all metaphases from 2 different metastases, but skin fibroblasts from the same patient had a normal chromosome complement. No common marker for human melanoma was found, but in 6 of the 8 cultures the most frequently found marker was formed by a brightly banded chromatid addition. Relative polysomy for Chromosome 7 was found in 7 of the 8 cultures and, for Chromosome 22, in 8 of the 8 cultures. The frequency of polysomy of Chromosomes 7 and 22 was significant at the 5% level.

Characterization of human maligant melanoma cell lines. I. Morphology and growth characteristics in culture

Seven human malignant melanoma lines were maintained in vitro for various periods of time. One line, established in this laboratory from a metastatic solid tumor by repeated treatment of the primary outgrowth with 0.02 percent EDTA, allowed a continuous culture of melanoma cells free of fibroblasts. By light microscopy, cells in each line could be classified into one of three morphologic types: elongated dendritic, cuboidal, or triangular dendritic. Four of the seven lines exhibited various degrees of pigmentation. The growth pattern was determined by plating efficiency and saturation density for each line. Cytogenetic analysis with the fluorescent banding technique revealed only human chromosomes with gross aneuploidy. Major marker chromosomes specific for each line were identified. None of the parameters studied showed any correlation or interdependence with one another, except for an association of elongated dendritic morphology with poor plating efficiency and low saturation density.

Erythropoietin-independent erythroid colony formation in vitro by hemopoietic cells of mice infected with friend virus

We have investigated the production of erythroid colonies in plasma culture by bone-marrow and spleen cells taken form C3Hf/Bi mice previously infected with a polycythemic strain of Friend virus (FV). Inclusion of erythropoietin (Epo) in the medium was found unnecessary for erythroid colony formation in vitro by these cells, although it was essential for the production of erythroid colonies by hemopoietic cells from normal animals. Development of erythroid colonies also proceeded umimpeded when cells from FV-infected animals were cultivated in medium pretreated with rabbit anti-serum that was shown to inactivate Epo. Thus, the hemopoietic tissues of FV-infected mice contained erythroid colony-forming units (CFU-Es) which appeared to be Epo-independent. When spleen cells from FV-infected mice were exposed to antiserum directed against syngeneic FV-infected spleen cells and complement, and then cultured with or without Epo, the number of erythroid colonies that developed was drastically reduced, indicating that the CFU-Es in these animals carried FV-induced antigen(s), and must themselves have been infected with virus. Electron microscopy of erythroid colonies produced by cells from FV-infected mice revealed the presence of budding and abundant free type-C virus particles. The efficiency of erythroid colony formation in vitro either with or without Epo by hemopoietic cells from FV-infected mice was substantially increased over that of cells from normal mice. The increase in the number of CFU-Es in these animals was due mainly to an increase in the number of Epo-independent CFU-Es. Epo-independent CFU-Es were first detected in bone marrow and spleen as early as 3 days after FV infection; thereafter their numbers progressively increased for at least 9 days. Hypertransfusion with red blood cells prior to FV infection reduced, while bleeding greatly increased, the efficiency of erythoid colony formation without Epo by cells from the spleens of the infected mice. The phenomenon of erythroid colony formation in plasma cultures lacking Epo provides a sensitive and reliable means of detecting Epo-independent CFU-Es, which appear to play a fundamental part in pathogenesis of the disease resulting from infection with the polycythemic strain of FV.

Light and electron microscopy of virus-associated, intranuclear paracrystals in cultured cells infected with types 2,4,6, and 18 human adenoviruses

Light and electron microscopic studies of human adenovirus types 2, 4, 6, and 18 infected HEp-2 cells revealed the induction of virus-associated, intranuclear paracrystalline formations. None of these crystalline structures were observed in abortively infected BHK-21 cells by these viruses. By histochemical techniques, the crystals only in Ad. 2 and Ad. 6 infected cells were visualized with the phase-contrast microscope and shown to be protein in nature but devoid of detectable amounts of nucleic acids. The crystals induced by Ad. 2 and Ad. 6 were frequently large, were polygonal in shape, appeared early after infection, and consisted of parallel tubules with a periodicity of 700 Å, whereas those induced by Ad. 4 and Ad. 18 were small, were irregular in shape, appeared later after infection, and consisted of parallel filaments with periodicities of 250 Å and 400 Å, respectively. Neither crystals nor virions were found in uninfected control cells. The relationship of the virus-associated crystals reported in the present study to those observed to date in other adenovirus–host systems was discussed.

Cytopathogenicity and replication of human adenovirus type 6 in cultured bovine cells

Multiplication of human adenovirus type 6 was demonstrated in established cultures of bovine cells. The virus replicated, producing characteristic cytopathic effects and undiminished infectivity, through six serial passages. By means of light and electron microscopy the appearance of viral inclusion bodies were comparable to those routinely observed in infected human cells. Intranuclear paracrystalline formations were also observed in the present virus–host system. The pathogenicity and host range of human adenovirus type 6 in relation to these properties of other adenoviruses were discussed.