Immunological studies on mouse mammary tumors. 3. Surface antigens reacting with tumor-specific antibodies in immune adherence

Different sensitivity of complement to Salmonella typhimurium accounts for the difference in natural resistance to murine typhoid between A/J and C57BL/6 mice

The difference in natural resistance to Salmonella typhimurium between S. typhimurium-resistant A/J mice and S. typhimurium-susceptible C57BL/6 mice was analyzed. In both strains, the growth of S. typhimurium was controlled in the spleen until 48 hr of infection, while serum C3b levels were increased in A/J mice immediately after infection but not in C57BL/6 mice. Incubation of A/J mouse serum with S. typhimurium or its lipopolysaccharide (LPS) generated sufficient amounts of C3b, but that of C57BL/6 mouse serum with them did not. A/J macrophages had higher intracellular killing activity in vitro than did C57BL/6 cells against S. typhimurium pre-opsonized with each corresponding fresh serum. However, the cells from both mice exhibited a similar level of killing activity against S. typhimurium pre-opsonized with fresh A/J serum or rabbit complement. The resistance of C57BL/6 mice was significantly increased by opsonizing S. typhimurium with fresh A/J serum or rabbit complement before inoculation. The serum level of interferon-gamma (IFN-gamma) in A/J mice was 2.7 times as high as in C57BL/6 mice at 48 hr post-infection. Recombinant murine IFN-gamma enhanced the intracellular killing activity of macrophages from both mice when S. typhimurium was pre-opsonized with fresh A/J serum but not with fresh C57BL/6 serum. These findings suggest that A/J macrophages exhibit maximal killing activity against A/J serum-opsonized S. typhimurium in vivo when the cells are activated with IFN-gamma. Therefore, the rapid and sufficient activation of complement by Salmonella LPS may render A/J mice more resistant against murine typhoid.

Comparison of the techniques used for monitoring humoral immunity in cancer patients

The humoral immune response to tumor-associated antigens (TAA) in cancer patients undergoing immunotherapy can vary considerably. This variability is inherent from patient to patient and is also dependent on the type of assay used to measure patient antibody response to tumors. In this investigation four serological techniques, complement-dependent antibody-mediated cytotoxicity, immune adherence, complement fixation, and indirect membrane immunofluorescence, were used to assess the humoral immune response in melanoma patients receiving specific immunization with cultured allogeneic melanoma cell vaccine. Two different patterns of antibody response were elicited. One was directed against TAA and oncofetal antigens (OFA) and the other was against HLA antigens. The sensitivity and reactivity varied among the different techniques suggesting that one test or technique may not be sufficient to evaluate critically a patient's response to immunotherapy.

Tumor production in the nude mouse, fibrinolytic activity and cross-reactivity with antimelanoma sera of various human tumor cell lines

It has been reported previously that antisera produced in non human primates against many cultured human melanoma lines recognize tumor-associated antigens on the melanoma cells. The reactivity correlated with other parameters of malignancy, such as rapidity of tumor growth in nude mice and release of plasminogen activator. In this study we have investigated whether these antisera also react with non melanoma cancer lines and searched for a correlation between this reaction and the other parameters of malignancy. There was cross-reactivity of the ten sera with 4-43% of the 46 non melanoma lines compared to 62-100% of the 16 melanoma lines, indicating a preferential reactivity with melanoma lines. For the non-melanoma lines no correlation was found between the release of plasminogen activator, the degree of tumorigenicity in the nude mouse or the reactivity of surface antigens as detected with antimelanoma sera.

Two new C3H mouse ascites tumor cell lines capable of proliferation in vivo and in suspension culture: morphological, karyological, kinetic and immunological properties

The establishment of mouse tumor cell lines capable of proliferating in vivo and in suspension culture was undertaken. The MM-46 tumor line, initiated from primary mammary carcinoma arising in a C3H/He mouse, was maintained for over 100 generations in the peritoneal cavities of syngenic mice. At the 50th generation of the tumor suspension, cultures were initiated. The established cell lines, designated TMT-1 and TMT-2, were characterized in vitro and in vivo. The morphological finding indicated that THT-1 and TMT-2 cells from mice closely resembled the MM-46 tumor cells. The oncogenic potential of the cultured cells was comparable to that of the original ascites tumor. The population doubling time of TMT-1 and TMT-2 cell lines was about 12 hr in mice, whereas the population doubling time of both cell lines lengthened to 20 hr in suspension culture. The increase in doubling time in culture was due to the prolongation of the G1 period. The cell lines, TMT-1 and TMT-2, whether fropm culture or mice, possessed colony forming ability in in soft agar medium. The colony forming ability of the cells decreased gradually through in vivo passages but it recovered upon recultivation of the cells from mouse to culture. Chromosome analysis and cytotoxicity test by anti-MM antiserum indicated that TMT-1 and TMT-2 cell lines closely resembled and had been derived from MM-46 tumor line. Therefore, it is possible to assay cell survival in vitro after in vivo experiments on these cells.

Immune adherence: a quantitative and kinetic analysis

Quantitative and kinetic analysis of the immune-adherence reaction (IA) between C3b fragments and IA receptors as an agglutination reaction is difficult. Analysis is possible, however, by use of radio-iodinated bovine serum albumin as antigen at low concentrations (less than 200 ng/ml) and optimal concentration of antibody to avoid precipitation of antigen--antibody complexes with human erythrocytes without participation of complement. Antigen and antibody are reacted at 37 degree C, complement is added, the mixture incubated and human erythrocytes added; after further incubation, ice-cold EDTA containing buffer is added and the erythrocytes centrifuged and assayed for radioactivity. Control cells reacted with heated guinea pig serum retained less than 5% of the added radioactivity. The method facilitates measurement of IA reactivity and permits more detailed analysis of the mechanism underlying the reaction.

Membrane associated antigens of human malignant melanoma. III. Specificity of human sera reacting with cultured melanoma cells

Sera from melanoma patients, healthy donors, pregnant women and patients with types of tumors other than melanoma were tested on various melanoma lines as well as on a cultured brain tumor and adult skin fibroblasts, using a microimmune adherence test. Positive reactions against all cell lines were found in serum from each group of donors. The degree of reactivity was dependent on the cell line used. Sequential absorption with AB Rh+ and pooled platelets of more than 200 donors either reduced the titer of sera or rendered a great part of the sera negative, demonstrating that antibodies against HL-A antigens and other tissue antigens were involved. The remaining positive sera were further absorbed with pooled cells from 6- to 8-week-old fetuses. This step abolished the reactivity of most sera, indicating the relatively high frequency of antibodies in males and females against fetal antigens expressed also on melanoma and other cells. In order to determine the specificity of the few remaining positive sera, absorptions with three different melanoma cell lines, a brain tumor and fibroblasts were carried out. The results showed only partial cross-reactivity between different cell lines. No evidence was obtained from this study for the existence of a common cross-reacting membrane-associated antigen on human malignant melanoma. Antigens that could be readily detected seemed mostly to be tumor-associated fetal antigens.

Immunologic and chemical studies on mucopolysaccharide derived from murine lymphosarcoma

Mucopolysaccharide was prepared from media in which the Gardner's lymphosarcoma cells were cultured. Multiple intraperitoneal injections of the preparation into syngeneic mice resulted in enhancement of the tumors which were inoculated prior to the injections. Sera of these hosts contained antibodies reacting with antigens of the outer layer of the tumor cells. Chemical analyses of the preparation showed that the mucopolysaccharide is composed of hexosamine, uronic, acid, hexose, and proteins. The mucopolysaccharide was shown to possess unique migration rate on electrophoresis and thin layer chromatography.

Antibodies and antigen expression in human melanoma detected by the immune adherence test

By means of a modified immune adherence (IA) technique, sera from melanoma patients were tested for the presence of antimelanoma antibodies. In total 13/73 sera tested showed a positive IA reaction of which 4/6 sera showed a positive reaction in the autologous situation. Sera from 33 patients with other tumors, 7 patients with non-neoplastic diseases and 50 healthy individuals did not show any IA reactivity towards melanoma cells. The reaction seemed to be selectively directed against tumor-associated antigens (TAA) on melanoma cells. No correlation with the stage of the disease could be found. Longitudinal studies indicated that conversions in antibody activity did not correlate with the clinical state of the patients. There was also no correlation with the corresponding in vitro data obtained in cell-mediated immunity tests. Cell lines and short-term cultures originating from tumors from different melanoma patients shared a common antigenicity. The expression of TAA on cells from a melanoma cell line fluctuated significantly during prolonged culture. The expression of TAA was influenced by the culture conditions and the growth state of the cells. A relation between TAA-expression and cell cycle phase was demonstrated.

Use of formalin-fixed melanoma cells for the detection of antibodies against surface antigens by a micro-immune adherence technique

Established malanoma cell lines were fixed in suspension with 4% formalin and tested for antigenic activity against sera from melanoma patients in a micro-immune adherence test. By incubation of formalin-fixed cells in serum-free medium the unspecific background rosette formation was substantially reduced to below 10%. As could be demonstrated in absorption experiments with viable and formalin-fixed tumor cells, surface antigens reacting with sera from melanoma patients are largely unaffected by formalin treatment.

Evidence for in vivo reaction of antibody and complement to surface antigens of human cancer cells

The immune adherence test was used to determine whether antibody and complement in cancer patients are fixed in vivo to tumor cells. Human erythrocytes adhered in vitro to the surface of human cancer cells obtained from autopsy and biopsy. Adherence was enhanced by further addition of the C2 and C3 components of complement, and was diminished by preliminary treatment with antibody to C3 (that is, to beta1C-globulin). The results suggest that tumor associated membrane antigens form complexes in vivo with antibodies and complement.

A series of hybrid cells containing different ratios of parental chromosomes formed by two steps of artificial fusion

Double hybridization of Ehrlich ascites tumor cells (ETC) and L cells was performed. In the first step, a hybrid (LE) of ETC and L(AG) (a mutant of L cells, resistant to 10 mug/ml of 8-azaguanine) and a hybrid (LL) of L(AG) and L(BrdU) (a mutant of L cells, resistant to 100 mug/ml of 5-bromodeoxyuridine) were prepared by the use of artificial fusion by UV-irradiated HVJ (Sendai virus). In the second step the LE hybrid and ETC, or the LL hybrid and ETC, were fused again by UV-HVJ. The hybrids (LEE and LLE) were segregated during culture. Thus, the series of hybrids L, LLE, LE, LEE, and ETC was obtained. The morphological feature and karyological characters of these hybrids and the distribution of antigens corresponding to each parent on their cell surfaces supported the above identification of the series of hybrids obtained by double hybridization. All three hybrids acquired new characters, such as the ability to form large colonies in soft agar and large tumors on the chorioallantoic membrane of chicken eggs, unlike either parent. The tumor-forming capacity of the series was ETC > LEE > LE > LLE; L cells formed no tumor in mouse abdomen under the test conditions.