The destruction of allogeneic tumour cells by antibody and adherent cells from peritoneal cavities of mice

A mononuclear phagocyte subset associated with cell necrosis in rheumatoid nodules: identification with monoclonal antibody 5.5

A subset of mononuclear phagocytes identified by mAb 5.5 has been found within rheumatoid subcutaneous nodules. These cells appear to be derived directly from blood-borne monocytes. They form a variable proportion of the mononuclear phagocyte population within the nodule and are intimately associated with the tissue necrosis which characterizes these lesions. Necrosis appears within small aggregates of mAb 5.5-positive cells. Similar cells are also associated with localized extensions of necrosis through the palisade zone. Centrifugal extension of the necrotic centers through incorporation of the inner cells of the palisade layer appears to be an independent phenomenon.

Higher ADCC of murine peritoneal cells after immunization with allogenic tumor cells as compared with stimulation by adriamycin, BCG, and thioglycolate

Normal peritoneal cells or spleen cells from C57BL mice could not lyse SRBC in an ADCC assay. After intraperitoneal injection of Adriamycin, BCG or thioglycolate the ADCC of peritoneal cells toward antibody-coated SRBC was elevated to 30% in contrast to the ADCC of spleen cells. However, peritoneal cells but not spleen cells of mice immunized with allogenic tumor cells (DBA SL2) showed ADCC levels at least two times higher than the levels observed after stimulation by other agents. Maximal ADCC levels (55.8%) were observed 10 to 15 days after immunization. Direct cytotoxicity towards SRBC increased to a maximum of 17.7% at 9 days after immunization. The effector cells in this system are thought to be macrophages, for ADCC activity was only present in the plastic-adherent cell fraction. Cell to cell contact was necessary for ADCC to occur; nonsensitized erythrocytes were not lysed when added to a mixture of effector cells and sensitized erythrocytes. Concentrations of antibody of 1 pg/ml were sufficient to induce ADCC, and effector cell to target cell ratios could be as low as 0.05. The finding that macrophages of mice immunized with allogenic tumor cells exhibit higher ADCC levels than macrophages elicited in other ways can contribute to the investigation of combined cancer therapy with antibodies and biological response modifiers.

A rapid alternative to the clonogenic assay for measuring antibody and complement-mediated killing of tumor cells

A study of the methods used to quantitate killing of tumor cells by antibody and complement has highlighted a number of problems. Using leukemia as a model we have found that the release of 51Cr from labeled tumor cells treated with antibody and complement can be an equivocal measure of cell viability. Combined with its restricted sensitivity (less than a 2 log range of cell killing) this makes this widely used assay of questionable value for detecting small numbers of viable cells, or for identifying subpopulations of complement-resistant cells. As an alternative we have developed a [125I]iododeoxyuridine (125IUdR) uptake assay, that combines the simplicity and rapidity of the 51Cr release technique with the sensitivity of a clonogenic assay. This method eliminates the problem of spontaneous isotope release, inherent in prelabeling assays, and variability from experiment to experiment can be avoided by including a viable cell standard curve within each assay. The sensitivity of the 125IUdR uptake method, which can be completed within a day, is similar to that of a 10 day methylcellulose cloning assay and was capable of detecting the presence of a minor subpopulation of complement-resistant tumor cells.

Role of activated macrophages in antibody-dependent lysis of tumor cells

Treatment of mice with Bacille Calmette-Guérin (BCG) or C parvum activates their peritoneal macrophages to release increased amounts of H2O2, and thereby to lyse extracellular tumor cells, in response to a pharmacologic agent, phorbol myristate acetate (PMA) (1-3). In the present study, the same bacterial vaccines activated peritoneal cells to become cytolytic to lymphoma cells sensitized with alloantiserum, in the absence of PMA. Resident peritoneal cells, or those elicited with thioglycollate broth, were ineffective, not only in PMA-induced lysis, but also in antibody-dependent lysis of tumor cells. The cytolytic effect of BCG peritoneal cells toward sensitized tumor cells appeared to be mediated mostly by macrophages. Cytotoxicity was immunologically specific, contact dependent, rapid, and efficient. Phagocytosis of intact tumor cells was not involved. Alloantiserum-dependent cytolysis was specifically blocked by the Fab fragment of a monoclonal antibody directed against the trypsin-resistant macrophage Fc receptor (FcR II). Thus, tumor cells coated with homologous immunoglobulin interact with FcR II on activated macrophages to trigger an extra-cellular cytolytic response.

Protein-A antibody-binding TPAAB) technique for detection of tumor-associated membrane antigen (TAMA) of Lewis lung carcinoma

Xenoantisera were prepared in rabbits against intact paraformaldehyde-fixed Lewis lung carcinoma (LLCa) cells and membrane solubilized proteins extracted with Triton X-100 and 3M KCI. The antisera were analyzed for antibodies to tumor-associated membrane antigens (TAMA) by means of a solid-phase radioimmunoassay (RIA). THe immunoassay employed 125-labelled Staphylococcus aureus protein A (SPA) to detect specific antibody binding to glutaraldehyde-fixed Lewis lung tumor target cells. The protein-A antibody-binding (PAAB) method is rapid, sensitive and reproducible. The PAAB revealed a possible LLCa-TAMA as evidenced by the reactivity of xenoantisera raised to LL paraformaldehyde tumor cell vaccine (TCV) and LL tumor Triton X-100 (TTri) and 3M KCI (TKCI) extracts of membrane preparations. The reactivity of our antisera followed linear dose-response kinetics but the degree of reactivity decreased from anti-TCV to anti-TTri to anti-TKCI respectively. The LL-TAMA demonstrated specificity since our antisera did not significantly cross-react with normal C56BL/6 cellular antigens or other known murine tumor-associated surface antigens of virally and chemically-induced tumor systems.

Demonstration of antibody-associated cellular cytotoxicity in patients with acute myelogenous leukemia before and after chemotherapy

This study demonstrates that a cytotoxic serum reactivity not requiring the presence of complement appears in the sera of patients with acute myelogenous leukemia. The reaction is detected upon short-term incubation of sera in vitro with autochthonous mononuclear white blood cells from peripheral venous blood of patients at the acute stage of the disease. This reactivity was demonstrated in 18/18 patients. Generally, the cytotoxicity was low in patients at the acute stage of the disease, but increased after chemotherapy and reached the highest level at the onset of clinical remission or just before. No cytotoxicity could be demonstrated against autochthonous remission white blood cells. The serum activity could be absorbed and eluted from protein A-sepharose CL-4B and was recovered in the 7S-fraction of the sera after gel filtration on Sephadex G-200 and ion exchange chromatography. This indicates that the demonstrated cytotoxicity is due to immunoglobulins of IgG-class. It is believed that Fc-receptor-bearing cells present in the target cell preparations function as effector cells. The reaction is designated antibody-associated cellular cytotoxicity (AACC).

Antibody-dependent cellular cytotoxicity against tumor cells. I. Cultivated bone marrow-derived macrophages kill tumor targets

Mouse bone marrow cells are cultivated in a liquid culture system in the presence of fibroblast conditioned medium. Under these conditions, proliferation of macrophage and granulocyte precursor cells is induced. Cells of a 5-day-old culture are shown to act as cytotoxic effector cells against tumor targets such as P815, E14, YAC and L5178Y. The effector cell is of macrophage origin since it is susceptible to treatment with the alloantiserum Mph-1.2 plus complement. The kinetics of the reaction resembles the kinetics for killer (K) lymphocyte lysis. In contrast to bone marrow cells, peritoneal macrophages do not show cytotoxic activity against antibody-coated tumor targets although they are susceptible to activation to cytotoxicity by lymphokines. The possible relationship of bone marrow effector cells and K lymphocytes is discussed.

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.

ADCC effector cells in a murine adenocarcinoma. I. Evidence for blood-borne bone-marrow-derived monocytes

The origin and identity of effector cells for anti-body-dependent cell-mediated cytotoxicity and/or growth inhibition (ADCC) found in the murine mammary adenocarcinoma T1699 were investigated. Non-phagocytic, non-adherent ADCC effector cells were identified in bone marrow, peripheral blood and the host fraction of the tumor but not from lymphoid organs. These cells were shown to be distinct from the specific growth-inhibitory "armed monocytes" also identified in situ. The ADCC effector cells possess low levels of EA Fc receptors and appear to express a macrophage-associated antigen. Both the bone-marrow and the in situ effector cells became phagocytic after overnight incubation, providing further evidence for the monocyte-macrophage lineage of these cells. The results suggest that bone-marrow-derived blood-borne monocytes are the principal ADCC effector cells localizing in the mammary adenocarcinoma T1699. The parallels between tumor-induced immunity and cellular resistance to infectious agents involving hypersensitivity reactions and blood-borne monocytes are discussed.

Quantitation of antibody-complement mediated lysis of tumor cells

An assay for quantitating antibody-complement mediated killing based on the release of 125I from 125IUdR labelled target cell is described. The temporal delay between antibody--complement damage and the release of nuclear material was shortened by treatment of the cells with a combination of trypsin and DNase. This treatment increased the rate of release of the labelled nuclear material from damaged cells without causing labelled nuclear material to be released from undamaged cells. The low level of spontaneous release of 125I from the target cells allows this assay to be used for experiments carried out over long time periods or in experiments involving extensive manipulations of the cells.