Anti-viral activity induced by culturing lymphocytes with tumor-derived or virus-transformed cells. Enhancement of human natural killer cell activity by interferon and antagonistic inhibition of susceptibility of target cells to lysis

The role of interferon in immediate hypersensitivity and autoimmune diseases

We have presented evidence showing that interferon can enhance the IgE-mediated release of histamine. We have also shown that immune interferon is present in the circulation of patients with certain autoimmune diseases. Furthermore, there is a positive correlation between active systemic lupus erythematosus and interferon levels. Systemic lupus erythematosus is characterized by immune hyperactivity. The continuous presence of type II, immune interferon in the circulation of these patients may, on one hand, contribute to the immunological aberrations, while on the other hand, protect against viral infections. At the present time we are looking for interferon in the circulation of patients with other autoimmune disorders.

Isolation of human NK cells by density gradient centrifugation

Sedimentation characteristics of human NK cells in discontinuous Percoll density gradients were studied. NK activity against the leukaemic cell line K-562 peaked in a single low density fraction mainly consisting of large granular lymphocytes previously shown to be the principal NK cells in human peripheral blood. Percoll density gradient centrifugation provides a useful tool for analysis of human NK cells and their relationship to other blood mononuclear cells.

Protective effect of interferon on target cells exposed to cellular cytotoxicity

In order to explore by immunological methods the interferon-induced cell membrane modulation, the effect of interferon in parental and monkey-mouse hybrid cells was studied in the presence of sensitized lymphocytes from isologous mice. After primary immunization to the hybrids, both parental interferons increased the lymphocyte-induced specific cytotoxicity in the same hybrid cells used as targets. In addition, a significnt increase of spontaneous lysis due to the two interferons was observed. In contrast, after secondary sensitization, in spite of the higher specific cytotoxicity induced by the lymphocytes, the same interferon preparation significantly protected the cells. These results are probably related to a greater number of sensitized effector cells after secondary sensitizationn. It is likely that, although interferon increases the affinity of sensitized T lymphocytes for the target cell membrane, in case of unsuccessful encounters, the target cells become resistant to new hits. Interferon could augment the number of such immune cells.

Transfer of interferon-induced viral resistance from human leukocytes to other cell types

Nonsensitized human leukocytes cocultured with various xenogeneic epithelioid and fibroblastic cells produced human leukocyte interferon and shortly thereafter transferred antiviral activity to the xenogeneic cells. Antiviral activity in the cocultured xenogeneic cells was not due to cell-mediated cytotoxicity as measured by specific 51Cr release and staining with vital dyes. The transfer of antiviral activity from leukocytes to xenogeneic cells was blocked by rabbit antiserum to human leukocyte interferon. Transferred viral resistance failed to develop in actinomycin D-treated xenogeneic cells, even though these cells induced human leukocyte interferon. Based on these findings, it appears that interferon made in the cocultures acts on the leukocytes to effect the transfer of interferon-induced viral resistance to the xenogenic cells, possibly by transmission of an inducer for the antiviral state. These studies strongly suggest a new and efficient host defense against virus infection which does not require killing of noninfected or recently infected cells.

Human peripheral null lymphocytes. II. Producers of type-1 interferon upon stimulation with tumor cells, Herpes simplex virus and Corynebacterium parvum

Human blood lymphocytes, exposed for 6 to 24 h in vitro to tumor cells (K 562, IGR3, L1210), Herpes simplex virus type 1 (HSV) or Corynebacterium parvum (CP), produced high levels of anti-viral activity which was identified as type-1 interferon (IF). In mixed lymphocyte tumor cell cultures (MLTC), the generated type-1 IF was definitely shown to originate from the lymphocytes and not from the tumor cells. Supplementation of leukocyte cultures with 10% fetal calf serum instead 10% human AB serum had little influence on tumor cell-induced IF production, but strongly reduced CP-induced IF production. Lymphocyte fractionation procedures involving iron/plastic treatment, nylon wool columns, Ig-anti-Ig columns and rosette (E, EA) separation led to the identification of null cells as highly efficient producers of type-1 IF. T cells obtained by different ways (E-rosette sedimentation, passage through 1 nylon and 2 Ig-anti-Ig columns, or thoracic duct lymphocytes) were poor IF producers in response to tumor cells, HSV and CP, but secreted anti-viral activity when stimulated with phytohemagglutinin. In MLTC, the level of generated type-1 IF roughly stimulated with phytohemagglutinin. In MLTC, the level of generated type-1 IF roughly paralleled nautral killer (NK) cell activity. Evidence is presented that type-1 IF can be produced by an Fc receptor-negative null cell subset, whereas NK activity requires Fc receptor-positive cells. It is suggested that production of type-1 IF represents one of the earliest functions in the differentiation process of mononuclear phagocytes and is likely to develop before the appearance of Fc receptors, diffuse esterase staining and latex phagocytosis.

Mode of regulation of natural killer cell activity by interferon

Whereas xenogeneic tumors such as baby hamster kidney or HeLa cells grow in nude mice, the same cells persistently infected with a variety of viruses are rejected. Spleen cells from normal nude mice were found to be induced to produce interferon and to exert natural killer (NK) activity on virus persistently infected (PI) tumor cells, and not on uninfected parental cells in vitro. The phenotype of the interferon-producing cells and the NK effector cells was found to be the same namely, Qa 5(+), Ly 5(+), ganglio-N- tetraosylceramide, with 35 percent of the NK cells also expressing Thy 1.2. NK activity against virus PI tumor cell lines could be nonspecifically augmented both in vivo and in vitro by prior contact with virus PI tumor cells. It was unambiguously demonstrated with chemically homogeneous mouse interferon that interferon, and not a contaminant, was responsible for the augmentation of NK activity in vitro. Studies on the mode of interferon action in augmenting NK activity revealed that the target cell for interferon action was serologically distinct from the NK effector cell. Anti-Ly 5 + complement (C)-treated spleen cells were depleted of NK activity and the ability to produce interferon, but, upon incubation with interferon for 1-3 h, regained both NK activity and susceptibility to anti-Ly 5 + C. Treatment with anti-Qa 5 + C eliminated NK activity, which could not be restored by the addition of interferon. We conclude that interferon produced by Ly 5(+) cells in response to virus PI tumor cells acts on Ly 5(-) precursor cells and induces their differentiation into functional Ly 5(+) NK effector cells.

Study of the mechanism for in vitro activation of mouse NK cells by interferon

The enhancement of the lytic capacity of mouse splenic 'natural killer' (NK) cells by interferon has been studied in vitro as a model for NK cell differentiation from inactive immediate precursors. We show that the increased cytotoxicity is a function of interferon concentration, and that two stages in the NK cell differentiation pathway can be distinguished. The first, very brief, can be performed at 0 degree C and without protein synthesis and probably corresponds to the fixation of interferon on its cell surface receptors. The second, resulting from the inductive signal given by interferon, proceeds for several hours and requires both RNA and protein synthesis. Our results also indicate that target cells for interferon-induced cytotoxicity are cells with 'null' characteristics, similar to the mature NK cells. Finally, they suggest that no soluble intermediary factor other than interferon is involved in the enhancing of NK cell cytotoxicity.

Factors affecting stimulation of natural cytotoxicity to a rat lymphoma by Corynebacterium parvum

Differences were seen in the ability of 2 strains of C. parvum to augment cytotoxicity attributable to NK cells towards a rat lymphoma. Furthermore, 2 batches of the same strain of C. parvum prepared by different methods also differed in their ability to augment cytotoxicity. Other factors influencing cytotoxicity were dose, route of inoculation and time after injection at which the assay was performed. Although all preparations of C. parvum augmented the cytotoxicity of peritoneal-exudate cells when injected i.p., only the most stimulatory preparation consistently augmented splenic cytotoxicity when given by this route. I.v. administration of 1 mg of C. parvum produced peak levels of splenic cytotoxicity 2-3 days later, but this response was strictly dose-dependent, since 1 microgram depressed splenic cytotoxicity. This dose-dependent effect also extended to ADCC, since 1 mg stimulated cytotoxicity towards antibody-coated P815 cells, whilst 1 microgram depressed it in a manner similar to its effect on natural cytotoxicity. Whilst the cytotoxic cells of stimulated rats closely resembled the NK cells of normal rats, BN rats responded differently to C. parvum from W/Fu or WAG rats, in that marked lysis of P815 or RBL-5 cells was observed, though these targets are usually resistant to lysis by rat NK cells in short-term assays.

Natural killer activity of lymphoid cells isolated from human ascitic ovarian tumors

Lymphocytes and tumor cells were isolated from the carcinomatous ascites of 24 patients with epithelial ovarian tumors by stepwise application of density and velocity sedimentation on discontinuous Ficoll-Isopaque gradients and fetal bovine serum. Tumor-associated lymphocytes showed a lower percentage of cells with receptors for sheep erythrocytes (E) or for complement than did peripheral blood lymphocytes from the same patients. NK activity was measured, 51Cr-labelled K562 cells being used as targets in a 20-h assay. Tumor-associated lymphocytes showed significant NK activity. Cytotoxicity levels were lower than for peripheral blood effector cells from the same patients, and these in turn showed significantly lower cytotoxic capacity than peripheral blood lymphocytes from 64 control subjects. Similar results were obtained when lysis was measured after 4 h of incubation. Tumor-associated lymphocytes forming E rosettes were at least as effective as the unseparated population. When tumor-associated lymphocytes were mixed with normal effector cells, in three of six preparations with low NK activity tested, significant inhibition of normal lymphocyte NK activity was observed. Adherent macrophages from carcinomatous ascites, which contained lymphocytes that had suppressive activity, showed no inhibitory activity. Interferon (IF) boosted the NK activity against K562 of tumor-associated lymphocytes. Purified ovarian carcinoma cells were relatively resistant to lysis by normal lymphocytes. However, they inhibited lysis of K562 cells in cold target competition assays, though less efficiently than K 562 itself, and were consistently lysed when effector cells were stimulated with IF. It is therefore suggested that ovarian carcinoma cells express NK-relevant recognition structures, but are relatively resistant to cytolysis by unstimulated effector cells.

Modulation of target cell susceptibility to human natural killer cells by interferon

The spontaneous cytolytic activity of human peripheral blood lymphocytes in a short-term 51chromium release assay was markedly enhanced by pretreatment with partially purified "Namalva" lymphoblastoid (type I) interferon (IF), provided that the target cells, five lymphoblastoid cell lines of variable natural killer (NK) sensitivity (K562, Molt 4, CCRF/CEM, Raji and Bri8), were not similarly treated with IF. When the targets were pre-exposed to comparable concentrations of IF, their susceptibility to lysis by IF-stimulated or unstimulated effectors was diminished, while exposure of both effectors and targets to IF for the duration of the cytotoxicity assay produced levels of cytotoxicity intermediate between those obtained when either effectors or targets were pretreated. The results indicate that, depending on the experimental design. IF is capable of exerting a protective effect on certain targets, a conclusion supported by competition assays wherein IF-treated cold K562 cells competed less successfully than untreated cold K562 cells for lysis of their radiolabelled counterparts by both IF-stimulated and unstimulated effectors. The data suggest that certain lymphoblastoid targets, in common with effector lymphocytes, possess receptors for IF. Some possible biological implications of the protective interaction of IF with tumour targets, which is antagonistic to that on effector cells, are discussed.

Receptors for immunoglobulin isotype on T and B lymphocytes from untreated patients with chronic lymphocytic leukaemia

Peripheral blood lymphocytes from eighteen untreated patients with chronic lymphocytic leukaemia (CLL) were analysed for the proportions of T and B lymphocytes with receptors for IgM, IgG or IgA. T lymphocytes with Fc receptors for IgM (T mu cells) or IgA (T alpha) cells were found in proportions comparable to those found in the controls. However, the proportion of T lymphocytes with receptors for IgG (T gamma cells) was significantly increased (P < 0.001) resulting in an abnormally low ratio of T mu/T gamma (P < 0.001), when compared with normal controls. The proportion of B cells bearing Fc receptors for IgM, IgG or IgA was determined simultaneously. No significant differences were found between the normal controls and the patients with CLL. In vitro treatment of the purified T and B lymphocyte preparations with human leucocyte interferon, did not alter the proportions of the lymphocytes expressing Fc receptors for various immunoglobulin isotypes. The significance of these findings is discussed.

Role of alloantigens in natural killing. Allogeneic but not autologous tumor biopsy cells are sensitive for interferon-induced cytotoxicity of human blood lymphcoytes

Blood lymphocytes of patients with solid tumors were assayed for cytotoxicity against autologous and allogeneic primary tumor cells. The lymphocytes killed autologous tumor cells in 7 of 25 cases (28%) and allogeneic tumor cells in 2 of 37 tests (5%). Lymphocytes from healthy donors were rarely cytotoxic for the biopsy cells, which indicates that these cells have low natural kill sensitivity. The autoreactivity that may reflect the immunological recognition of tumor cells was not altered by pretreatment of the effectors with interferon (IF). In contrast, killing of allogeneic tumor biopsy cells was induced by IF in approximately 50% of tests, with the lymphocytes of both the tumor patients and the healthy donors. The mechanism of the alloreactivity is most likely a consequence of IF-induced polyclonal activation of cytotoxic potential and the lymphocytes that are committed to recognize the alloantigens expressed on the particular target manifest the killing function. When the biopsy cells were explanted and kept in culture for 5-6 d, their susceptibility for the lymphocyte damage increased, and they were killed by the IF-treated cells also in autologous combinations. Whether this change in sensitivity is a result of qualitative or quantitative changes in antigen expression or of other changes in the properties of the cell membrane is unknown.

Immune interferon secretion as an expression of immunological memory to transplantation antigens: in vivo generation of long-lived, recirculating memory cells

Leukocytes from C57Bl/6 mice immunized against DBA/2 strain antigens by intraperitoneal injection of mastocytoma P 815 cells produced, when stimulated in the mixed leukocyte reaction assay with DBA/2 spleen cells, an earlier and more intense secretion of immune interferon than leukocytes from untreated mice. This secondary-type interferon response was independent of cell proliferation. The memory phenomenon was induced by long-lived, recirculating lymphocytes found in spleen, lymph nodes and thoracic duct, but not in the thymus. Memory cells could be recruited into inflammatory sites. They were shown to be specific for H-2 alloantigens, although some cross-reactivity with stimulating cells bearing unrelated H-2 antigens was observed. The possible anti-tumor, antiviral and immunoregulatory roles of this memory phenomenon, and its significance in transplantation immunity are discussed.

Inhibition by interferon of Sendai virus cytolysis

Treatment of HeLa cells with human interferons inhibited 51Cr release from cells induced by ultraviolet-inactivated Sendai virus. The inhibitory effect became apparent about 6 h after interferon treatment and persisted for 24 to 48 h. In the interferon-treated cells, the cytolysis was inhibited within 10 min after adding virus and the inhibitory action was suppressed by the treatment of the cells with cycloheximide. Mock interferon and mouse interferon did not inhibit the cytolysis and antiinterferon serum neutralized the effect of interferon. All these findings indicate that Sendai virus-induced cytolysis is inhibited by interferon per se. However, interferon did not have any influence on Sendai virus hemolysis.

Augmentation of cell-mediated cytotoxicity to a rat lymphoma. III. In vitro stimulation of natural killer cells by a soluble factor

The in vitro cytotoxicity of rat natural killer cells was augmented by the incubation of normal spleen cells with a soluble factor derived from the 24-h culture of spleen cells and various tumour cells. Cytotoxicity was augmented approximately 4-, 3- or 2-fold depending on whether the spleen cells were incubated with the factor for 18 or 3 h or during the course of the cytotoxicity assay respectively. The factor was produced in cultures containing syngeneic, allogeneic or xenogeneic tumours and no correlation was observed between the ability of tumour cells to induce the production of the factor and their susceptibility to lysis in the 4-h cytotoxicity assay. The factor was produced in cultures of spleen cells of several rat strains, and it stimulated the cytotoxicity of syngeneic and allogeneic spleen cells. The cells responsive to stimulation closely resembled NK cells of normal rats. Culture supernatants containing the stimulatory factor possessed anti-viral activity, and evidence suggested that NK cells were stimulated by a factor resembling a type-I interferon. The relevance of these findings to the stimulation of NK cells by tumours in vivo is discussed.

Natural killer cell activity associated with reticulum cell neoplasms

A marked increase in natural killer (NK) activity is observed with lymphoid cells prepared from SJL/J mouse spleen and lymph nodes, in which a transplantable reticulum-cell neoplasm (RCN) is growing. The killer cells are non-adherent, non-phagocytic, relatively resistant to X-ray, and scarcely or only partially inactivated by treatment with anti-Thy 1.2 serum and complement. The killer activity is directed against a wide variety of tumor target cells, not requiring homology in histocompatibility, but is selective and not indiscriminate. Kinetics of in vivo development on NK activity, competitive inhibition of in vitro cytotoxicity by target cells and their membrane extracts are described. The NK activity appears to increase in parallel with the infiltration and growth of RCN in these organs. No such augmented NK activity was observed with other types of tumors that grew in these organs of SJL/J mice. (C57BL/6 X SJL/J)F1 mice pretreated with silica to abrogate Hh restriction and subsequently injected with RCN of SJL/J (H-2s) origin supported the growth of transplanted RCN. The high NK activity associated with this RCN was markedly reduced by in vitro treatment with anti-H2b serum plus complement, indicating the host origin of NK cells. However, the close association of RCN growth with elevated NK activity may indicate a special function of RCN in promoting NK activity by an unknown mechanism(s) of cellular interactions.

Dysfunction of natural killer cells in multiple sclerosis: a possible pathogenetic factor

Natural killer (NK) cell activity, antibody-dependent cytotoxicity (ADCC) and the effect of interferon on NK activity was investigated in multiple sclerosis (MS) patients. NK activity measured against K-562 tumour cell line was found to be significantly low in MS patients, and this was most pronounced in the group of male patients with definitive disease. The response of NK cells to interferon proved to be impaired and almost no activation could be demonstrated in response to polyinosinic-polycytidylic acid (poly I:C). Preliminary data obtained by the determination of interferon production in several definitive MS cases reflect a defect in the interferon producing capacity of lymphocytes. The possible involvement of impaired NK cell function in the aetiopathogenesis of MS is discussed.

Enhancement of human natural cell-mediated cytotoxicity by interferon

The effect of exogenous Namalva interferon (IF) on the natural killer (NK) cell activity of human blood lymphocytes was examined against 5 target cell lines (K562, CCRF/CEM, Molt 4, Raji and Bri8) using the 51Cr-release assay. Addition of IF to the test significantly increased the cytotoxicity, though not as much as when effector cells were treated with IF before the test. Augmentation of cytotoxicity was evident after only 1 h pretreatment and was maximal by 6 h. The rate of lysis of susceptible targets by IF-treated effectors markedly exceeded that by their untreated counterparts. Separation of lymphocyte subpopulations (by SRBC-rosette sedimentation and nylon-fibre column filtration) demonstrated that the activities of IF-stimulated and unstimulated cells were similarly distributed, suggesting that the major effect of IF is enhancement of the activity of pre-existing NK cells rather than generation of new populations of effectors. Target cell lines with high and low susceptibility to NK cells showed increased cytotoxicity by IF-treated effector cells. These findings may be relevant to the current discussion of the role of NK cells in immunosurveillance against neoplasia.

Interferon as a mediator of human lymphocyte suppression

Evidence is presented that interferon (IF) is a major mediator of the human concanavalin A (Con A) suppressor cell. The suppressive effects of Con A-activated lymphocytes on the mitogen responses of normal responder cells were largely abrogated by addition of anti-human leukocyte IF serum. Similar suppressor activity was generated by coculture of peripheral blood leukocytes (PBL) with a melanoma cell line (MeWo) and a HeLa cell line persistently infected with measles virus that induced the production of IF by lymphocytes. A human mammary carcinoma line (MCF-7) and two bladder carcinoma lines (T24 and TCCSUP) failed to induce IF or suppression. Addition of anti-human leukocyte IF serum to suppressor cells and supernates from tumor cell-lymphocyte cocultures largely abolished suppression and neutralized the antiviral activity of such supernates. Exposure of PBL from purified protein derivative (PPD)-positive donors to PPD caused the production of suppressor activity and IF. PBL from PPD-negative donors failed to produce significant amounts of IF or to suppress on exposure to PPD. Supernates from PBL treated with virus (Newcastle disease virus [NDV]) contained IF and suppressed the mitogen responses of responder PBL. Both the suppressive and the antiviral activities of this material were eliminated after treatment with anti-IF serum. To ascertain whether antiviral and suppressive activities were mediated by the same types of IF, supernates from PBL cultured with Con A, PPD, NDV, and tumor cells were treated with anti-IF serum or acid pH. In all cases antiviral activity was neutralized in parallel with abrogation of suppressor activity. These results provide strong evidence for the role of IF as a mediator of human suppressor cell activity.

Requirement for monocytes in the spontaneous cytotoxic effects of human lymphocytes against non-lymphoid target cells

Human lymphocytes have been shown to lyse in vitro a large variety of target cells derived from tumour as well as normal tissues. The effector cells involved in this spontaneous cell-mediated cytotoxicity (SCMC) have generally been characterised as lymphocytes which lack surface membrane immunoglobulin (sIg) and lack or express only low-affinity receptors for sheep red blood cells (SRBC), but possess receptors for the Fc portion of IgG (refs 3--7). We have previously shown that monocytes may be involved in SCMC, as strong depletions of adherent cells always resulted in a reduction in SCMC. In the present study, experiments were undertaken to determine the role of monocytes in SCMC. Evidence is presented that monocytes have a helper function in the lymphocyte-mediated SCMC against target cells growing in monolayer cultures, whereas effector cells in SCMC against lymphoid target cells growing in suspension cultures were lysed by lymphocytes in the absence of monocytes.

Spontaneous cytotoxicity of murine cells treated with the interferon inducers BRL 5907 and BRL 10739

The effects of the polyribonucleotide interferon inducers, BRL 5907 and BRL 10739, on the spontaneous cytotoxicity of CBA mouse cells towards the allogeneic lymphoma EL-4, were investigated. Intravenous administration of BRL 5907 and BRL 10739 increased the cytotoxic activity of a non-adherent, theta-negative, surface immunoglobulin-negative cell present in the spleen, but had no effect on cells in the lymph nodes. Spleen cell cytotoxicity was established within 24 h of injection of the polyribonucleotides, but had disappeared by 4 days. In addition, injection of mice with BRL 10739 increased the spontaneous cytotoxicity of a nylon-wool-adherent, theta-positive spleen cell. Intraperitoneal injection of mice with BRL 5907 and BRL 10739 also enhanced the cytotoxic activity of a non-adherent peritoneal exudate cell.

The requirement for monocytes in spontaneous cytotoxicity by lymphocytes from healthy donors and melanoma patients

Lymphocytes from 12 healthy donors were depleted of monocytes by velocity sedimentation at unit gravity (average monocyte contamination 0.2%) and tested for spontaneous cytotoxicity (SC) against tumor target cells in 23 h microcytotoxicity assays. Sixty percent of all lymphocytes were recovered in this monocyte-depleted lymphocyte fraction (LF). In contrast, with the corresponding unfractionated lymphocytes (UL) the LF cells were not spontaneously cytotoxic on T24 bladder carcinoma, NKI-1, NKI-7, NKI-8, NKI-10 melanoma, and MC-1 mammary carcinoma cell line cells and target cells derived from two short-term melanona cultures (Me 215 and Me 223). SC of the LF could be restored by reconstitution with autologous monocytes, which were obtained > 80% pure in the same velocity sedimentation procedure. Addition of 4-8% monocytes was sufficient to restore the SC of the LF to the level achieved with the corresponding UL, whereas maximal induction of SC was observed after addition of 8-16% monocytes. Higher numbers of monocytes had suboptimal effects. SC of the LF could also be restored by monocyte culture supernatants. The spontaneous cytotoxic effector cells were characterized as non-E rosette-forming, membrane sIg-negative Fc-receptor-bearing lymphocytes, a proportion of which probably also bear C3-receptors. Since the LF was not spontaneously cytotoxic, in spite of the presence of Fc-receptor bearing lymphocytes, it is concluded that monocyte help, mediated via soluble factors, is required. Evidence is presented that the lack of SC by the LF might be attributable to the failure of these cells to make appropriate contact with the target cells. LF/target cell contact followed by target cell kill occurred after addition of monocytes. Effector/target cell contacts, artificially established by agglutinins, did not result in target cell kill. Thus the effector/target cell contacts observed in the presence of monocytes suggest recognition of particular membraner determinants involved in SC. An identical requirement for monocytes was observed with LF cells from 5 stage 1 and 5 stage 11 melanoma patients tested for SC against both melanoma and non-melanoma target cells. This indicates that either the cytotoxicity against melanoma cells with lymphocytes from melanoma patients is of the same nature as the SC of lymphocytes from healthy donors, or that specific melanoma-associated cellular cytotoxicioty also requires monocyte help.

Bestatin treatment and the peripheral lymphocyte population in cancer patients

Bestatin, a substance produced by Streptomyces olivoreticuli, inhibits certain cell-membrane-associated enzymes and has been shown to augment immune responses in experimental animals. We have determined whether bestatin medication changed the peripheral lymphocyte population in 15 advanced cancer patients. After 2 weeks of daily, 30 mg oral bestatin medication, the lymphocyte counts remained essentially unchanged, but the frequency of E-rosette-forming lymphocytes increased. In vitro stimulation of the lymphocytes with PHA or PPD remained essentially unchanged while the natural-killer activity of the lymphocyte population increased in most patients. Bestatin treatment caused no detectable side effects.

Natural killer activity in peripheral lymphocyte population following local radiation therapy

The natural killer (NK) activity of peripheral lymphocytes against 51Cr-labelled Chang or K562 cells was tested using a 4 h release assay before and after postoperative radiation therapy for mammary carcinoma. NK activity against K562 was significantly reduced at completion of therapy (a total target dose of 45.0 Gy) and restituted 3 to 4 months later. NK activity against Change cells exhibited a slight but non-significant decline at completion of therapy followed by an overshoot 3 to 4 months later. The frequency of Fc-IgG receptor bearing lymphocytes was decreased at completion of therapy and largely restored after 3 to 4 months.

Antibody-mediated destruction of virus-infected cells

This chapter describes the effect of antibody on virus-infected cells with special reference to the human system. The destruction by antibody of the infected cells through the mediation of complement is described in detail based in considerable part on the contributions of the authors. Activation of the alternative pathway by the various infected cells is of special interest. The interesting effect of the antibody-dependent cell-mediated cytotoxicity (ADCC) system involving viral antigens in cell killing is also presented. Multiple additional topics are also covered, such as the effect of antibody on the expression of viral proteins both on the surface of the cell and intracellularly. Serum antibody, produced in response to virus infections, is of major importance in preventing the spread of infection by virtue of neutralizing free virus in extracellular fluids. Virus neutralization by antibody is enhanced by complement. Antibody binding to the surface of virus-infected cells can affect virus production and release in the absence of an effector system. Immunoglobulin (IgG) antibody can mediate the destruction of virus-infected cells in conjunction with complement or cytotoxic lymphocytes. In addition, at a conceptual level there is evidence to suggest that antibody may enhance and confer specificity on basic nonspecific humoral and cell-mediated defense mechanisms.

Cell-mediated cytotoxicity during vaccinia virus revaccination in man: influence of antibodies and interferon

Seven healthy human adults were revaccinated with vaccinia virus. Cell-mediated cytotoxicity to vaccinia virus-infected fibroblasts was investigated on the day of vaccination and on days with peak activity. Three donors were studied until day 30 after vaccination. The addition of interferon to cytotoxicity reactions resulted in an increase in killing. This increase was not seen when antibodies were added. When a mixture of lymphocytes from a revaccinated and a non-revaccinated donor was used as effector cells, the killing observed corresponded to the killing seen with lymphocytes from the revaccinated donor, when tested alone. This finding indicates that no antibodies or other soluble mediators capable of increasing cytotoxicity are released from the lymphocytes during the cytotoxicity assay.

Comparison of natural killer cells induced by Kunjin virus and Corynebacterium parvum with those occurring naturally in nude mice

Natural killer (NK) cells are rapidly elicited in the spleen and peritoneal cavity of mice inoculated intravenously or intraperitoneally with live Kunjin virus, and more slowly in the peritoneal cavity of mice inoculated intraperitoneally with Formalin-inactivated Corynebacterium parvum. NK cells induced by either agent display cytotoxicity for a similar spectrum of syngeneic, allogeneic, and xenogeneic cultured cell lines. By contrast, the cells occurring naturally in the spleen of congenitally athymic (nude) mice show substantially lower NK activity and are cytotoxic for a more restricted range of target cell lines. The distinction suggests that there may be more than one type of NK cell or that activation enhances the cytotoxicity and perhaps broadens the range of target specificity of endogenous NK cells.

Characteristics and genetic control of NK-cell-mediated cytotoxicity activated by naturally acquired infection in the mouse

Most and perhaps all natural-cell-mediated cytotoxicity (NCMC) may be activated by a response to exogenous infections. Specific-pathogen-free (SPF) mice have little or no natural killer (NK) cell activity, but when they are relocated in conventional conditions, they develop strong NCMC within 2 to 3 days. Unlike other SPF animals, hypothymic nude mice display good NCMC which is further augmented upon their entry into a pathogenic environment. The ontogeny, genetic control and other features of pathogen-activated NCMC resemble those previously described for NK cells. An H2-D region NCMC regulatory gene is active in either a homozygous or heterozygous state, but to be operative seems to require the presence of an additional complementing locus, which maps outside the H-2 complex. It is proposed that H-2 influences NCMC levels by affecting the expression or immunogenicity of NK cell-activating determinants. Recently activated NK cells were non-adherent and lacked Ia and Thy-1 determinants. NCMC was not affected by treatment with monoclonal high-titer Thy-1.2 antisera and complement. However, an Ly-6.2 antiserum did contain anti-NK cytotoxic activity, which was shown by absorption analysis to be distinct from anti-Ly-6.2 activity. The NK antigen has a strain distribution pattern distinct from Ly-5 and other Ly markers, but may be related or identical to NK-1.

Augmentation of cell-mediated cytotoxicity to a rat lymphoma. I. Stimulation of non-T-cell cytotoxicity in vivo by tumour cells

The injection of a syngeneic Gross-virus-induced lymphoma into W/Fu rats induced peaks of cytotoxicity in the spleen attributable to non-T cells and T cells 3 and 10 days later, respectively. The conditions required for augmenting the cytotoxicity of the non-T cells in various lymphoid compartments (shown elsewhere to closely resemble NK cells) were analysed using the ip and iv routes of inoculation and a variety of tumour cells including those normally susceptible or resistant to lysis by NK cells in vitro. Using an ip inoculation of W/FuG-1 cells (a tumour susceptible to lysis by NK cells), a short-lived, 3-fold increase in cytotoxicity was observed in the spleen at day 3 and a 5-fold increase in the PEC at day 5. Cytotoxicity in other lymphoid organs remained unchanged. Tumours resistant to lysis by NK cells also stimulated cytotoxicity in the spleen or PEC, although the effect depended on the dose and route of inoculation used, and depression of cytotoxicity was observed under some conditions.

Augmentation of cell-mediated cytotoxicity to a rat lymphoma. II. Characterization of the non-T cytotoxic cells stimulated in vivo by tumour cells as natural killer cells

A variety of tumours injected into rats were found to rapidly stimulate cytotoxicity which was similar to naturally-occurring cytotoxicity of normal rats. Cytotoxic cells from the spleen and peritoneal cavity closely resembled NK cells in their lytic specificity and cell-surface characteristics. Thus, although cytotoxicity could be stimulated "non-specifically" with tumours which were resistant to lysis in vitro by NK cells, the cytotoxic cells exhibited patterns of specificity against a panel of target cells in direct lysis or competitive inhibition assays which were similar to those of NK cells from normal rats. These cells also closely resembled NK cells in being largely non-adherent, non-T cells, and in exhibiting a similar heterogeneity in the expression of Fc receptors. Thus, cytotoxicity which was augmented shortly after tumour inoculation appeared to be attributable to NK cells. However, whilst the majority of NK cells from normal or tumour-inoculated rats shared these properties, significant heterogeneity was observed. Minor populations of cytotoxic cells were adherent, were lysed by a heterologous anti-T-cell antiserum and complement and did not express an Fc receptor, although it was not determined whether the same subpopulation possessed all three characteristics.

Immune interferon in the circulation of patients with autoimmune disease

The observation that type II, or immune, interferon could be produced by peripheral-blood leukocytes in vitro on an immune-specific basis suggested that it also might be produced in vivo in various autoimmune disorders. We found immune interferon in the serums of patients with systemic lupus erythematosus, rheumatoid arthritis, scleroderma and Sjögren's syndrome. Among 28 patients with systemic lupus erythematosus, 71 per cent of those with active and 21 per cent of those with inactive disease showed interferon in their serums. Serial serum samples showed a good correlation between interferon titers and disease activity. Moreover, interferon titers correlated positively with antibodies to DNA and negatively with serum levels of the third component of complement. It is possible that the production of interferon may contribute to immunologic aberrations in auto-immune diseases and also protect the already compromised host from viral infections.

Interferon and cell-mediated immunity

The thesis is introduced that the phenomena of cell-mediated immunity proceed with the necessary involvement of interferon. In view of this thesis various examples of cell-mediated cytotoxicity both antibody-dependent, and antibody-independent are analyzed. The role of interferon in transplantation, allergic diseases and the treatment of cancer is also discussed. Based on this analysis it is concluded that interferon provides for the cytotoxicity of immune and non-immune leukocytes. It is suggested that interferon is responsible for the cytotoxic effect in itself, since it facilitates lethal hybridization. Recognition of the important role of interferon in the mechanism of cell-mediated immunity leads to some practical conclusions: a) The selective inhibition of the activity of type II interferon may be a sufficient measure in cases where now total immunosuppression is applied. b) Periodic treatment of healthy population by lymphokine stimulants may be a method of prevention of cancer. c) Transplantation, allergic diseases, immunotherapy of cancer should be considered in terms of the role of interferon in these processes.

Interferon and spontaneous cytotoxicity in man. III. Effect of interferon on lymphocytes and target cells in vitro

Human leukocyte interferon (IF) was tested for its capacity to modify the spontaneous cytotoxicity of human peripheral lymphocytes for allogeneic target cells in vitro. Pretreatment of lymphocytes with IF augmented their cytotoxicity whereas pretreatment of the target cells did not increase but possibly decreased their sensitivity to the spontaneous cytotoxicity of lymphocytes.

Mechanism of rejection of virus persistently infected tumor cells by athymic nude mice

Cell lines known to be tumorigenic in the nude mouse were modified by rendering them persistently infected (P.I.) with a variety of RNA viruses, including measles, mumps, vesicular stomatitis virus, and influenza. Although as few as 100 HeLa or BHK cells produced tumors in 100% of nude mice, as many as 2 x 10(7) of the same cells P.I. with viruses failed to produce tumors. An active host response responsible for restricting the growth of the P.I. cells was suggested by the findings of marked mononuclear cell infiltrates at the inoculation sites and the inability of irradiated nude mice to reject them. An analysis of the in vitro cytotoxic activity of spleen cells from normal nude mice indicated that: (a) P.I. cell lines, but not uninfected cell lines, were susceptible to spontaneous cytotoxicity; (b) in vivo inoculation of P.I. lines induced an enhanced cytotoxic activity for P.I. targets in vitro, and this induction was not specific either for inducing virus or cell line; and (c) the effector cell had the characteristics for natural killer (NK) cells. Although the specificity of recognition of the various P.I. cell lines remains unclear, cold competition experiments indicated that blocking the killing of one P.I. cell line, e.g. HeLa-measles, could be achieved only by unlabeled homologous cells, i.e. HeLa-measles, and not by uninfected cells or other P.I. lines. A variant subline of BHK cells P.I. with VSV was selected for its ability to withstand the rejection process in nude mice. These cells formed metastatic and invasive tumors in nude mice. Although they were the most potent inducers in vivo of NK cell activity against various P.I. targets, they were the most resistant of the P.I. lines to NK cell cytotoxicity in vitro. In this system there was a good correlation between tumor rejection in vivo and susceptibility to NK cells in vitro. The present results suggest that NK cells may play a significant role in both rejection of tumor cells, and in resistance to viruses, particularly persistent infections.