In vitro and in vivo investigations on antibody-dependent cellular cytotoxicity

Colony-stimulating factor enhancement of myeloid effector cell cytotoxicity towards neuroectodermal tumour cells

We conducted experiments to determine the optimal conditions for colony-stimulating factor-enhanced neutrophil- and mononuclear phagocyte-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) using monoclonal antibodies to disialogangliosides expressed on neuroectodermal tumour target cells. Neutrophil ADCC was most effective at effector:target ratios of 100:1, with maximal cytotoxic responses to melanoma target cells generated by 3 h. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) were the most potent stimulators of neutrophil ADCC, and enhanced ADCC activity was inhibited in the presence of antibody to Fc receptor type II (FcRII). GM-CSF and macrophage colony-stimulating factor (M-CSF) treatment of freshly isolated monocytes inhibited antibody-independent cytotoxicity but enhanced antibody-dependent responses. After 3 d in culture with CSF, 3-10-fold enhancement of ADCC against melanoma target cells was observed at effector:target cell ratios of 10:1. Greatest stimulation of macrophage ADCC was obtained when GM-CSF, M-CSF or interleukin 3 (IL-3) were used in conjunction with a secondary stimulus. Although gamma interferon (gamma-IFN) did not augment the cytotoxic capability of GM-CSF- and IL-3-stimulated macrophages, prominent cytotoxic enhancement was seen when M-CSF-stimulated macrophages were exposed to gamma-IFN. A chimaeric mouse/human monoclonal antibody was found to be equivalent in activity to the murine antibody in neutrophil ADCC; however, in macrophage ADCC assays with submaximal effector cell stimulation, the chimaeric antibody was associated with a two-fold greater response. These studies indicate that under specific conditions, CSFs capable of increasing the number and functional activity of mature myeloid effector cells enhance antibody-dependent cytotoxicity to neuroectodermal tumour target cells.

Neutrophil cytotoxicity induced by immune complexes prepared with cationized antibodies

Here we analyse the ability of soluble immune complexes (IC) prepared with cationized antibodies to induce cytotoxic responses mediated by neutrophils. While cationized IC induced high levels of cytotoxicity, control IC induced very low levels of response. Inhibition of cytotoxicity by catalase but not by three haemenzyme inhibitors suggests that oxygen-dependent but myeloperoxidase-independent mechanisms are responsible for cytolysis. While the response induced by control IC was enhanced by cytochalasin B and was not modified by colchicine, that induced by cationized IC was markedly inhibited by cytochalasin B and significantly enhanced by colchicine. Cytotoxicity induced by cationized IC was completely abrogated by monoclonal antibodies to Fc gamma RII. Using control IC, a partial inhibition was observed employing either anti-Fc gamma RII or anti-Fc gamma RIII monoclonal antibodies. Treatment of neutrophils with chemotrypsin or pronase significantly enhanced cytotoxicity induced by cationized IC but not by control IC. We also found that non-specific absorptive mechanisms appear to play an important role in the binding of cationized IC, but not control IC, to the neutrophil surface. The significance of these results is discussed.

Effects of lipoxygenase and cyclooxygenase inhibitors on murine antibody-dependent cellular cytotoxicity (ADCC)

The purpose of this study was to determine the effects that specific inhibition of arachidonic acid (AA) metabolism has on the antibody-dependent cellular cytotoxicity (ADCC) of murine spleen cells. The action of three inhibitors of the lipoxygenase (LO) pathway--nordihydroguaiaretic acid (NDGA), esculetin (Es), and phenanthroline (Phe)--was compared with that of three inhibitors of the cyclooxygenase (CO) pathway--indomethacin (INDO), acetyl salicylic acid (ASA), and imidazole (IMI). All the LO inhibitors suppressed ADCC function in a dose-dependent manner, but NDGA was the most potent inhibitor of this cytolytic activity. In fact, NDGA inhibited the ADCC function with 97% inhibition at 100 microM, while Phe and Es, at the same concentration, inhibited ADCC by 21% and 19%, respectively. However, CO inhibitors did not markedly affect ADCC function and only some doses of them had a slight, but significant, depressing effect (8-11% inhibition at 0.01-0.1 microM of INDO, 7% inhibition at 400 microM of ASA, and 13% inhibition at 800-1000 microM of IMI). These results suggest the LO pathway of the arachidonic acid metabolism plays an important role in regulating ADCC activity of murine spleen cells and the products of the CO pathway have little effect on ADCC lysis.

A case of facio-scapulo-humero-peroneal myopathy with inflammatory changes. Preliminary data on distribution of mononuclear cells in muscle tissue

We report the case of a 49 year old woman with clinical, electrophysiological and histochemical signs of facio-scapulohumeroperoneal dystrophy characterized by highly inflammatory changes. Lymphocyte typing by immunofluorescence and immunoperoxidase techniques on a muscle biopsy fragment revealed a large number of T8 cells at endomysial sites. There was no evidence of direct invasion of sound fibers by lymphocytes, which are thus unlikely to have exerted a primary cytotoxic action on the muscle tissue. Another finding was an increased number of macrophages in both endomysial and perivascular regions. Cell-mediated immunity did not play a significant role in the pathogenesis of our case, unlike other reported cases of polymyositis and facioscapulohumeral dystrophy with inflammatory findings.

Cellular cytotoxicity mediated by isotype-switch variants of a monoclonal antibody to human neuroblastoma

The biological property of an antibody is determined by its antigen binding characteristics and its isotype-related effector functions. We have established monoclonal antibodies of different isotypes by stepwise selection and cloning of the hybridoma CE7. The original CE7 secretes an IgG1/kappa (CE7 gamma 1) antibody that recognises a 185 kD cell surface glycoprotein expressed on all human sympatho-adrenomedullary cells. Isotype-switch variants were isolated in the following sequence: from the original CE7 gamma 1, CE7 gamma 2b variants were isolated, and from a CE7 gamma 2b variant CE7 gamma 2a variants were isolated. The antibodies of three different isotype variant cell lines possess identical antigen binding characteristics, but display distinct effector functions as demonstrated by antibody dependent cell-mediated cytotoxicity (ADCC). ADCC was performed with the neuroblastoma line IMR-32 as the target cells, and different FcR gamma positive cells were either freshly isolated from human peripheral blood leukocytes or cultured for 6-10 days and tested as potential effector cells. Tumour lysis mediated by monocyte-derived macrophages depended on the presence of CE7 gamma 2a antibodies; antibodies from the CE7 hybridomas of gamma 2b and gamma 1 isotypes were virtually inactive in ADCC assay. Pre-exposure of macrophages to rIFN-gamma enhanced their ADCC activity, a result that is compatible with the notion that the high affinity Fc IgG receptor (FcR gamma I/CD64) is involved in the triggering of ADCC in macrophages. In contrast to macrophages, mononuclear cells, nonadherent cells and monocytes displayed considerable non-specific lytic activity, which was little influenced by the presence of antibody regardless of the isotype added.

The immune response to vaccinia virus infection in mice: analysis of the role of antibody

Immune response to primary intraperitoneal infection with vaccinia virus (strain IHD-J) was studied in C3H/Hej mice. Antibodies reactive with virus structural proteins were detected 6 days and neutralizing antibodies 8 days after infection. Although serum antibodies from infected mice bound to vaccinia virus infected cells, these antibodies were ineffective in complement mediated lysis of infected cells and were only moderately active in experiments with antibody dependent cellular cytotoxicity (ADCC). Immunoblotting analysis showed that serum antibody reacted with a number of structural proteins of both intracellular and extracellular forms of vaccinia virus. Immunoprecipitation results showed antibody binding of nonstructural proteins and glycoproteins. Correlation of the kinetics of NK and CTL activities in infected mice with neutralizing antibodies indicated that the cellular functions clearly precede the appearance of serum neutralizing antibody. The resolution of primary infection in mice thus appears to be mediated by functions of cellular immunity while resistance to reinfection may be dependent on circulating neutralizing antibody.

The effects of scleroderma serum on human microvascular endothelial cells. Induction of antibody-dependent cellular cytotoxicity

To investigate the vascular immunopathology of systemic sclerosis, we developed a model consisting of human microvascular endothelial cells, leukocytes, and serum. Sera from 19% of the patients studied mediated antibody-dependent cellular cytotoxicity against endothelial cells. Some sera also mediated cytotoxicity against aortic endothelium and fibroblasts. K lymphocytes, the cells that mediate antibody-dependent cellular cytotoxicity, were identified in the skin of some patients. The sera alone were not cytotoxic or growth inhibitory, and did not affect endothelial prostacyclin production.

Monoclonal antibody analysis of mononuclear cells in myopathies. IV: Cell-mediated cytotoxicity and muscle fiber necrosis

Cell-mediated muscle fiber injury occurs in inclusion body myositis (IBM), polymyositis (PM), and even in Duchenne dystrophy (DD). Most of the autoaggressive cells are T cells and macrophages, but some are killer/natural killer (K/NK) cells. We here compare the frequencies per 1,000 muscle fibers of endomysial K/NK cells of varying cytotoxicity with those of T cells and macrophages in 8 cases each of IBM, PM, and DD. Two-micrometer serial cryostat sections were analyzed. The Leu-4 marker, present on all T cells and some K/NK cells, and the Leu-7 and Leu-11 markers, present on K/NK cells, were localized by paired immunofluorescence. Macrophages were demonstrated by the acid phosphatase reaction. In IBM, PM and DD, the respective average cell counts per 1,000 muscle fibers were: Leu-4+7- cells (T cells not expressing a K/NK marker)--710, 530, and 59; Leu-4+7+ cells (K/NK cells of low K/NK cytotoxicity)--294, 163, and 13; Leu-4-7+ cells (K/NK cells of intermediate cytotoxicity)--32, 10, and 2; and macrophages--292, 251, and 38. Leu-11+ K/NK cells that have the highest killing activity were virtually absent in all cases. The data suggest a limited role for antigen and major histocompatibility complex unrestricted K/NK cells, as compared with antigen-specific and major histocompatibility complex-restricted T cells, in IBM and PM. Further, the findings cast doubt on the significance of either T cells or K/NK cells in mature muscle in DD.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro effect of ethanol on cell-mediated cytotoxicity by murine spleen cells

The effects of ethanol on murine spleen cell-mediated lysis have been studied. Concentrations of 5.5-176 mM ethanol produced progressive inhibition of antibody-dependent cell-mediated cytotoxicity (ADCC). Binding of spleen cells to antibody-sensitized target cells was not inhibited by comparable concentrations of ethanol. Kinetic analysis revealed decreased rates of lysis with increasing concentrations of ethanol. Changes of effector to target cell ratios revealed an inhibition of maximum lysis and decreased lytic efficiency in the presence of 88 mM ethanol. Preincubation experiments showed the inhibitory effect of ethanol to be reversible. Macrophage-depleted spleen cells appeared to be as susceptible to inhibition by ethanol as unfractionated spleen cells. Ethanol also inhibited natural killer and alloimmune cytotoxic T cell activity. The ADCC data were analysed by using a mathematical model which incorporates the kinetics of lysis, dose-response relationships, heterogeneity of the lytic effectors, reversibility of inhibition and ethanol loss during incubation. An inhibition constant (KI) of 373 mM-2 when two ethanol molecules interact with the site of inhibition was calculated. 50% inhibition of lysis is produced by 52 mM (0.24%) ethanol. The results are consistent with a model which assumes that lysis is due to a critical number of interactions which ultimately trigger the lytic event. Alcohol interferes with lysis by reacting with sites which are required for triggering the lytic event. Although the molecular details of the mechanism of inhibition are as yet undefined, we infer that ethanol inhibits ADCC at the programming for lysis or the lethal hit stages.

The role of serologically defined epitopes on mumps virus HN-glycoprotein in the induction of virus-dependent cell-mediated cytotoxicity. Analysis with monoclonal antibodies

The importance of virus structural proteins for the induction of virus-dependent cellular cytotoxicity (VDCC) was studied by means of monoclonal antibodies raised in mice against mumps virions. Antibodies against the viral glycoprotein bearing the haemagglutination and neuraminidase activities (HN) inhibited VDCC but not the natural cytotoxicity (NK) displayed by the lymphocytes in the absence of virus. Antibodies to the fusion factor, the membrane protein or the nucleoprotein were inactive. These results confirmed our previous conclusion, that the only viral component required for VDCC induction is the HN protein. To clarify the role of this protein in VDCC further, the inhibitory activity of 13 HN-specific monoclonals, all of IgG isotype and directed against 9 distinct determinants, was studied in detail. Seven antibodies reacting with 3 different determinants of the peptide moiety of the HN protein were strongly inhibitory. The remaining antibodies, specific for 5 additional peptide epitopes, had intermediate or weak inhibitory effects. One carbohydrate specific anti-HN antibody was inactive although its antigen-binding capacity was of the same magnitude as that of a good inhibitory antibody. The anti-HN antibodies inhibited VDCC regardless of their IgG subclass. Moreover, VDCC inhibition was not correlated with the capacity of the antibodies to inhibit haemagglutination, haemolysis, neuraminidase activity, or the infectivity of the virus. These results suggest that full expression of VDCC requires the interaction of more than one of the serologically defined structures of the HN polypeptide with virus receptors on the lymphocytes and probably also on the target cells. These structures may be different at least in part from those involved in other known biological activities of the virus. Treatment of lymphocytes with virus increases both the number of target-binding cells (TBC) and the number of cytotoxic effector cells. However, when treated under conditions which gave optimal VDCC inhibition, none of the inhibitory antibodies reduced the virus-mediated increase in TBC. This indicates either that the anti-HN antibodies decreased the efficiency of effector-target cell interaction necessary for VDCC induction, or that they blocked a post-binding step required for triggering of cytotoxicity.

Virus-dependent cellular cytotoxicity in vitro. Mechanisms of induction and effector cell characterization

When human peripheral blood lymphocytes were incubated with 51Cr-labelled tissue culture cells (T24 bladder carcinoma cells or Chang liver cells), their natural cytotoxicity (NK) usually stopped after 8 h of incubation. The 51Cr release induced by lymphocytes treated with small amounts of live or ultraviolet-inactivated mumps virus was strongly enhanced and lasted longer. When the lymphocytes were fractionated by Percoll gradient centrifugation, the highest NK activity was found in the low-density fraction enriched in large granular lymphocytes, whereas that of the T-cell-enriched high-density fractions was low. In contrast, the virus-dependent cellular cytotoxic (VDCC) activity was more evenly distributed between these fractions. However, there was a difference between the target cells in that the T24 cells were more susceptible to the cytotoxicity of lymphocytes in the high-density fractions than the Chang cells. Studies of Percoll fractions in the single-cell agarose assay showed that virus treatment increased the proportion of both target binding cells and killer cells in all fractions. Moreover, in the high-density fractions the increase in the number of killer cells was greater than that in binding cells, suggesting that the enhanced target cell killing induced by the virions reflected both increased binding and effector cell activation. Surface marker analysis of unfractionated lymphocytes indicated that the number of T3+ effector cells was greater than that of the HNK-1+ effector cells, regardless of whether the lymphocytes were treated with virus or not. However, for both NK and VDCC, the T3 to HNK-1 distribution ratio on the effector cells was 5-8:1 for T24 and 2:1 for Chang. Taken together, the results indicate that both NK and VDCC effector cells are phenotypically heterogeneous and that the target cells may play an active role in the recruitment of those effector cells that are most efficient in that system. The enhancement of lymphocyte cytotoxicity primarily reflects effector cell recruitment.

Mumps virus-induced enhancement of the in vitro cytotoxicity of cord blood lymphocytes

Purified lymphocytes from the umbilical cord of healthy donors (CBL) displayed lower natural cytotoxicity (NK) and antibody-dependent cellular cytotoxicity (ADCC) than peripheral blood (PBL) from adult donors. In contrast, CBL treated with small amounts of UV-inactivated or live mumps virions expressed the same level of enhanced cytotoxicity (virus-dependent cytotoxicity (VDCC)) against non-infected target cells as PBL. For individual CBL donors there was no correlation between the level of NK and VDCC, indicating involvement of partly distinct effector cell populations. The heterogeneity of the effector cells active in VDCC was confirmed by cell fractionation experiments. The major CBL effector cells in NK and ADCC were found in 'non-T' lymphocyte fractions and/or in fractions containing cells with high-avidity receptors for IgG. In contrast, CBL fractions consisting of about 100% lymphocytes bearing T-cell markers and depleted of Fc gamma R+ cells were strongly cytotoxic in VDCC when T24 cells (human bladder carcinoma) were the targets. With two other target cell types of similar susceptibility to VDCC, the cytotoxic activity of T-cell-containing fractions was less pronounced, indicating that the target cells play an active role in effector cell selection. The surface marker profiles of the VDCC effector cells were the same for CBL and adult PBL. Incubation of CBL with UV-inactivated virions usually gave no significant stimulation of DNA synthesis above that seen in virus-free controls. Taken together, our results suggest that neither specific recognition of viral antigen by T cells nor mitogenic effects of viral material are involved in VDCC generation.

The role of viral glycoproteins in mumps virus-mediated antibody-dependent cellular cytotoxity in vitro

Treatment of human peripheral blood lymphocytes with live or UV-inactivated mumps virions enhances antibody-mediated cellular cytotoxicity (ADCC), reflected by increased target cell lysis in a 51Cr-release assay or an increased number of plaque-forming cells on monolayers of bovine erythrocytes (Eb) in the presence of anti-Eb antibodies. Virus treatment of the Eb targets causes a similar enhancement. The role of viral glycoproteins in ADCC enhancement was investigated by using a panel of monoclonal antibodies raised in mice against mumps virions. Most of the lymphocytes bound mumps virions, as ascertained by indirect immunofluorescence. A high proportion of virus-treated lymphocytes also formed rosettes with Eb. Anti-HN antibodies inhibited rosetting to various degrees. Although antibodies with high haemagglutination inhibition titres were most efficient inhibitors, antibodies without this serological activity were also inhibitory. Anti-F antibodies were only weakly inhibitory, and anti-NP antibodies had no effect. Anti-HN antibodies also abrogated target cell lysis in the 51Cr-release assay and effector cell recruitment in the ADCC plaque assay by inhibiting virus-mediated Eb-lymphocyte interactions both at the target cell and at the effector cell level. Anti-F or anti-NP antibodies were only weakly or not at all inhibitory. The results suggest that virus-mediated enhancement of ADCC is caused by the HN glycoprotein, primarily (although perhaps not exclusively) by its improvement of the effector cell-target cell contacts necessary for the efficient execution of target cell lysis.

Monoclonal antibody analysis of mononuclear cells in myopathies. I: Quantitation of subsets according to diagnosis and sites of accumulation and demonstration and counts of muscle fibers invaded by T cells

In 76 muscle specimens (normal controls, 9; Duchenne dystrophy, 11; scleroderma, 11; dermatomyositis, 13; polymyositis, 15; inclusion body myositis, 17), mononuclear cells were analyzed at perivascular, perimysial, and endomysial sites of accumulation. Monoclonal antibodies reactive for B cells, T cells, T cell subsets, killer (K) or natural killer (NK) cells, and the Ia antigen were used for cell typing. Macrophages were identified by the acid phosphatase reaction. Few extravascular mononuclear cells occurred in normal muscle. In all inflammatory myopathies, a mixed exudate of T cells, B cells, and macrophages was present. Mature K/NK cells were rare in all diseases. In dermatomyositis, polymyositis, and inclusion body myositis, there was a positive gradient for T cells, T8+ cells, and activated T cells and a negative gradient for B cells and T4+ cells between perivascular and endomysial sites. In scleroderma the predominant perimysial exudate consisted mostly of T cells and macrophages. The percentage of B cells at all sites, and the T4+/T cell ratio in the endomysium, were significantly higher in dermatomyositis than in the other diseases. In polymyositis and inclusion body myositis, the endomysial exudate contained a large number of T cells, T8+ cells, and activated T cells but only sparse B cells. T cells accompanied by macrophages focally surrounded and invaded nonnecrotic fibers in polymyositis and inclusion body myositis. Rare fibers in Duchenne dystrophy and a very few fibers in dermatomyositis and scleroderma were similarly affected. We infer that (1) T-B, T-T, and T-macrophage cooperativities are likely to exist in muscle in different myopathies; (2) T cell-mediated fiber injury plays a role in polymyositis and inclusion body myositis; (3) T cell-mediated fiber injury can also occur in inherited diseases, such as Duchenne dystrophy; and (4) a local humoral response may occur in muscle in dermatomyositis and possibly in polymyositis and inclusion body myositis.

Lymphocyte function in patients with chronic glomerulonephritis. Tests of suppressive activity generation by concanavalin A and antibody-dependent cellular cytotoxicity

Lymphocyte suppressive activity after stimulation with Con A and lymphocyte function as the effectors in the ADCC test had been examined in 68 patients with chronic glomerulonephritis (GN) and in 20 healthy controls. Lymphocyte suppressive activity was lower in patients with chronic GN than in the healthy individuals. In regard to chronic proliferative GN and mesangial GN the difference was statistically significant. The lymphocyte efficiency in the ADCC test was generally adequate in patients with chronic GN and none of the morphological types showed significant deviation from the control group. In the general analysis of patients with chronic proliferative, mesangial, membrano-proliferative and membranous GN a decrease of lymphocyte suppressive activity below the lower standard limit has been detected (45% of cases). A similar defect in lymphocyte function in the ADCC test has been found in 18.6%. A statistically significant relationship between the lymphocyte function disorders and the high clinical dynamism of GN has been noticed, although in some cases there was a deviation from this tendency. It is supposed that circulating immune complexes, detected in some patients with chronic GN are not the only decisive factors responsible for defects in lymphocyte function.

Modulation of antitumoral antibody-dependent cellular cytotoxicity and natural killer activity by Adriamycin and daunorubicin

Mouse effector cells isolated from various anatomical sources failed to mediate antibody-dependent cellular cytotoxicity (ADCC) against alloantiserum-coated L1210 murine leukemia cell targets, whereas rat spleen cells appeared to be potent mediators of this activity. Following suppression of effector cell function 3 days after a single drug injection, the nylon wool non-adherent population of rat spleen cells from daunorubicin (DM)-treated rats demonstrated an increased ability to mediate ADCC compared to controls. Alternatively, although suppression occurred at day 7, no rebound enhancement was demonstrated by the same cell population isolated from Adriamycin (AM)-treated animals for as long as 12 days post-injection. Natural killer (NK) activity, measured as the ability of the nylon wool non-adherent rat spleen cell population to lyse uncoated L1210 cells, was modulated by drug treatment in a similar manner at each time point although the changes were not significant. In contrast to NK cells for which a substantial amount of activity remained adherent to nylon wool, all K cell activity was found in the non-adherent spleen cell population. The effector cell, in both cases, was not susceptible to antithymocyte serum plus complement treatment; however, NK activity appeared trypsin-sensitive whereas K cell activity did not. Therefore, AM and DM demonstrated different activities with regard to in vivo modulation of antitumoral ADCC.

Antibody-dependent cellular cytotoxicity to allogeneic but not autologous erythroblasts in vitro

Antibody-dependent cellular cytotoxicity (ADCC) is a very sensitive mechanism for immune injury of target cells, which utilizes extremely low concentrations of antibody. We have developed a method for demonstrating this type of cytotoxicity to normal human erythroblasts. The latter were enriched 3- to 4-fold and were then labeled with 59Fe. Blood lymphocytes from the same donor were enriched to 93% and were added as effector cells at a 60:1 ratio to the target cells. After 4 hr at 37 degrees C, as 5- to 10-fold increase in the release of 59Fe occurred when the plasma or IgG from patients with pure red-cell aplasia was present. This activity was not present when the effector cells were absent. However, this activity was found in the remission plasmas of patients and was not found when autologous erythroblasts were used. These studies demonstrate a method for detecting ADCC to allogeneic normal human erythroblasts. This ADCC does not appear to be related to the disease since a similar autoimmune activity to the patients' own erythroid cells was not detected. Further studies are suggested using other effector cells in this system.

Monocyte and granulocyte-mediated tumor cell destruction. A role for the hydrogen peroxide-myeloperoxidase-chloride system

Human monocytes stimulated with phorbol myristate acetate were able to destroy a T lymphoblast cell target (CEM). Stimulated human granulocytes were also capable of mediating CEM cytotoxicity to a comparable degree as the monocyte. CEM destruction was dependent on the pH and the effector cell number. Both monocyte or granulocyte mediated cytotoxicity were inhibited by the addition of catalase, whereas superoxide dismutase had no inhibitory effect. In addition, CEM were protected from cytolysis by the effector cells by the myeloperoxidase inhibitors, azide and cyanide, or by performing the experiment under halide-free conditions. Glucose oxidase, an enzyme system capable of generating hydrogen peroxide, did not mediate CEM cytotoxicity, while the addition of purified myeloperoxidase dramatically enhanced cytolysis. Hypochlorous acid scavengers prevented CEM destruction by the glucose oxidase-myeloperoxidase-chloride system but neither hydroxyl radical nor singlet oxygen scavengers had any protective effect. These hypochlorous acid scavengers were also successful in inhibiting monocyte or granulocyte-mediated CEM cytotoxicity. Based on these observations we propose that human monocytes or granulocytes can utilize the hydrogen peroxide-myeloperoxidase-chloride system to generate hypochlorous acid or species of similar reactivity as a potential mediator of CEM destruction.

IgA antibody, antibody-dependent cellular cytotoxicity and prognosis in patients with nasopharyngeal carcinoma

Immunoglobulin fractions containing antibodies to the Epstein-Barr virus (EBV) were isolated from different sera and tested in the antibody-dependent cellular cytotoxicity (ADCC) assay. All cytotoxic activity resided in the IgG fraction. IgA antibodies were not cytotoxic in this assay against cells expressing the EBV-induced membrane antigen complex. However, IgA antibodies were able to block the IgG-mediated ADCC reaction, indicating that the IgA and IgG antibodies recognized the same EVB-specific antigenic determinants. This was supported by results from radioimmune precipitation experiments. Our findings suggest that low ADCC titers previously identified in the sera of patients with nasopharyngeal carcinoma (NPC) who had a poor prognosis could be due to the blocking activity of IgA antibodies. The results further suggest that IgA antibodies are detrimental to the patient with this disease, if one assumes that ADCC functions in vivo in immunity to this tumor

Humoral and cell-mediated immune mechanisms in the production of pathology in avirulent Semliki Forest virus encephalitis

Seven days after peripheral inoculation with an avirulent strain of Semliki Forest virus, the brains of CBA and nude mice exhibited a mononuclear inflammation and spongiform degeneration. Mice that had received cyclophosphamide (150 mg/kg) 24 h after infection showed no pathology until day 11. However, immunofluorescence studies of the brains of immunosuppressed, infected mice demonstrated viral antigen within the soma and processes of neurons at earlier periods. The brain lesions could be reconstituted on day 7 in immunosuppressed, infected recipients with 6-day immune spleen cells. Immune spleen cells depleted of T lymphocytes, the non-immunoglobulin-bearing population deficient in B lymphocytes, or immune sera plus nonimmune bone marrow cells could also reconstitute the lesions. However, inflammation and spongiform changes were reduced when donor immune cells were depleted of either T or B lymphocytes. When both T and B lymphocytes were removed from the donor immune population, recipient brains did not show pathology. The results demonstrate that either antibody or immune T cells can trigger pathology, but there is also participation of nonimmune bone marrow-derived mononuclear cells, probably of the monocyte-macrophage lineage.

Immune response in rabbits to surface components of extracellular and intracellular forms of vaccinia virus

The development of cellular as well as humoral immune response to extracellular and intracellular forms of vaccinia virus (ECV and ICV, respectively) and their surface antigens were studied in rabbits. Direct lymphocyte cytotoxicity and peripheral blood leukocyte migration inhibition tests were used to measure cell-mediated immune response, while neutralizing and hemagglutination-inhibiting antibodies were assayed for measuring humoral immune response. Direct cytotoxicity of lymphocytes from rabbits immunized with ECV or its surface proteins was demonstrable by day 7 after immunization, and by the end of week 3 it almost declined to pre-immunization levels. Inoculation with ICV or its surface proteins failed to induce lymphocyte cytotoxicity. In contrast, migration inhibition of peripheral blood leukocytes from rabbits immunized with ECV, ICV, or their surface proteins was observed with homologous antigens. However, leukocytes from rabbits immunized with ECV or its surface proteins also showed migration inhibition in the presence of ICV. Similarly, in the humoral immune response, neutralizing antibodies were produced against homologous as well as heterologous forms of virus despite immunization with purified preparations of ECV, ICV, or their surface proteins. Adsorption with purified ICV preparations abolished the neutralizing activity of these antisera against heterologous forms of virus. Hemagglutination-inhibiting antibodies, on the other hand, were produced only after immunization with ECV or its surface proteins. In addition, antibody-dependent cell-mediated cytotoxicity was employed to detect specific antibody response after immunization of rabbits with live virus, ECV, and ICV. Antisera raised against ECV or live virus supported antibody-dependent cell-mediated cytotoxicity, whereas ICV-antiserum failed to do so. The antibody activity present in the former antisera was abolished by absorption with cell membranes from vaccinia-infected cells but not with purified ICV. The data suggest that immunization with inactivated ECV seems to bring about interaction between host immune response (cellular and humoral) and virus-infected cells, which may, perhaps, be necessary for protection against pox virus infection. A similar interaction is unlikely to occur after immunization with inactivated ICV.

Natural and immune cytolysis of canine distemper virus-infected target cells

Natural and immune cytolysis of canine distemper virus (CDV)-infected target cells in vitro is described. Lymphocytes expressing natural cytotoxicity were found in specific-pathogen-free beagle dogs and in beagle-coonhound crosses before vaccination with CDV and indefinitely after vaccination, when the ephemeral immune lymphocyte-mediated cytotoxicity (ILMC) had declined. In contrast to the natural lymphocyte-mediated cytotoxicity, the ILMC was genetically restricted, could not be blocked by CDV-specific antibody, and was effective against measles virus-infected as well as CDV-infectd target cells. Lymphocyte populations were depleted of Fc receptor and surface immunoglobulin-bearing cells by rosetting techniques and tested in comparison. An antibody-dependent cell-mediated cytotoxicity was demostrated against CDV-infected target cells that were preincubated with CDV antibody when Fc receptor-bearing lymphocytes were not removed. The ILMC was measurable for approximately 10 days beginning at 6 days post-vaccination. In contrast, CDV antibody measured by virus neutralization and humoral cytotoxicity was detectable by 6 days postvaccination and persisted at peak levels for at least 5 months.

Antibody reactive in antibody-dependent cell-mediated cytotoxicity following influenza virus vaccination

The antibody reactive in antibody-dependent, cell-mediated cytotoxicity (ADCC) to influenza virus-infected cells was measured in two groups of seven volunteers each, before and after immunization with inactivated or live attenuated A/Victoria/3/75 influenza virus vaccines. Age-matched controls were seven adult individuals who experienced natural influenza infection due to A/Victoria/3/75-like virus strain. After inactivated whole influenza virus immunization all the subjects showed a significant rise of the antibody reactive in ADCC (from a mean value of 4.7% to 17.1% cytotoxicity, before and 5 weeks after immunization, respectively) as well as of hemagglutination inhibition (HI) antibody (fourfold or greater increase). These immune responses were similar to those observed among naturally infected controls. After live attenuated virus vaccination, no significant increase in titer of antibody reactive in ADCC was detected, even though the vaccine induced significant increase of HI antibody titer. Little correlation was found between ADCC and HI antibody rises in sera of recipients of inactivated virus vaccine and of naturally infected individuals while, in live attenuated influenza virus vaccines, the rise of HI antibody titer did not correspond to a significant increase of ADCC antibody titer did not show subjects who developed a significant rise in ADCC antibody titer did not show significant variation in antibody to neuraminidase and/or to complement fixation influenza virus antigens.

Oxidative mechanisms of monocyte-mediated cytotoxicity

Human monocytes stimulated with phorbol myristate acetate were able to rapidly destroy autologous erythrocyte targets. Monocyte-mediated cytotoxicity was related to phorbol myristate acetate concentration and monocyte number. Purified preparations of lymphocytes were incapable of mediating erythrocyte lysis in this system. The ability of phorbol myristate acetate-stimulated monocytes to lyse erythrocyte targets was markedly impaired by catalase or superoxide dismutase but not by heat-inactivated enzymes or albumin. Despite a simultaneous requirement for superoxide anion and hydrogen peroxide in the cytotoxic event, a variety of hydroxyl radical and singlet oxygen scavengers did not effect cytolysis. However, tryptophan significantly inhibited cytotoxicity. The myeloperoxidase inhibitor cyanide enhanced erythrocyte destruction, whereas azide reduced it modestly. The inability of cyanide to reduce cytotoxicity coupled with the protective effect of superoxide dismutase suggests that cytotoxicity is independent of the classic myeloperoxidase system. We conclude that monocytes, stimulated with phorbol myristate acetate, generate superoxide anion and hydrogen peroxide, which together play an integral role in this cytotoxic mechanism.

Epstein-Barr virus-specific antibody-dependent cellular cytotoxicity in patients with Burkitt's lymphoma

Coded sera from 54 patients with African Burkitt's lymphoma (BL) were titrated for antibodies against an Epstein-Barr virus (EBV)-induced membrane antigen in the antibody-dependent cellular cytotoxicity (ADCC) assay. The titers were then correlated with the progression of lymphoma growth following chemotherapy. In 74% of the patients with high ADCC titers (greater than 3,840), lymphomas showed partial or complete regression following therapy. In the medium-titered group (240-3,840), 36% of the lymphomas showed some response to therapy, while only 29% of the lymphomas in the low group (less than 240) responded to treatment. These preliminary results indicated that, as previously reported for patients with nasopharyngeal carcinoma, ADCC titers may be a prognotic value in patients with this EBV-associated disease. In an attempt to determine the identity of the ADCC antigen, some of these sera were examined for antibody to the four major MA components so far identified in the membrane of EBV-infected Raji cells. Sera with high ADCC titers in general contained antibody to the four major MA components, while low-titered sera usually contained antibody to three or less of these proteins. There were exceptions to this pattern, however, indicating that the ADCC antigen might differ from the four EBV-induced membrane components so far identified.

Cytotoxic immune response of meningioma patients towards allogeneic and autologous tumour cells before and after surgery

Cell-mediated cytotoxicity (CTX) of meningioma patients towards meningioma cells and fibroblasts was studied in vitro before and after surgery, using the 3H-proline microcytotoxicity test. When incubated with allogeneic target cells before surgery, lymphocytes from three out of seven donors showed a specific destruction of meningioma tissue, and two were cytotoxic on both types of targets. Five patients were tested against their own tumour and against skin fibroblasts; this was feasible by keeping their lymphocytes frozen in liquid nitrogen until their target cells grew as suitable monolayers in vitro. Three patients showed a specific cytotoxic response. After excision of the tumour a gradual loss of this reactivity was observed in both allogeneic and autologous systems. Sera of three patients, whose lymphocytes were not reactive against their own tumour, induced antibody-dependent cellular cytotoxicity (ADCC) towards autologous tumours if normal effector cells were used. This type of response was detectable mainly in postoperative sera, and could not be elicited in autologous lymphocytes. On the contrary, autologous sera inhibited CTX of meningioma effector cells. The data suggest that meningiomas can induce a complex immunological response in the host, which is dependent on the presence or absence of a large tumour burden.

Monoclonal antibodies in cell-mediated cytotoxicity against human melanoma and colorectal carcinoma

Hybridoma-derived monoclonal anti-melanoma antibodies and anti-colorectal carcinoma antibodies were found to mediate in vitro antibody dependent cell-mediated cytotoxicity (ADCC) reactions against melanoma and colorectal carcinoma cells, respectively. The antigen(s) detected in ADCC on melanoma cells maintained for more than one hundred passages in tissue culture were also found on two recently established melanoma cell lines. These antigens were not detected on skin fibroblasts of the same patients from whom the melanomas were obtained. The ADCC reactivities of anti-melanoma and anti-colorectal carcinoma antibodies were found to be specific for melanoma cells and colorectal carcinoma cells, respectively.