Specificiy of lymphocyte-mediated cytotoxicity induced by in vitro antibody-coated target cells

Immunosuppressive effect of tacrolimus (FK-506). Bone xenografts in rabbits

We examined the immunomodulatory effect of the macrolide antibiotic FK-506 (tacrolimus) in bone xenograft transplantation. Full-thickness pieces of iliac bone from mongrel dogs were transplanted into the iliac bone of Japanese white rabbits. FK-506 at a dose of 1.6 mg/kg/day was injected into the rabbits for 10 days after transplantation. In the animals treated with FK-506, inflammatory cell infiltration was remarkably reduced and revascularization accompanied by new bone formation occurred in the grafts. At 4 months after the transplantation, the formation of new bone and of mature new bone marrow were observed. In a control group, inflammatory cell infiltration was marked around the graft from 2 weeks after the transplantation. Revascularization from the recipient site to the graft in the control group was poor and only a small amount of new bone had formed at 4 months. Our findings suggest that short-term administration of FK-506 has a beneficial effect on experimental xenograft bone transplantation.

Cellular rejection in discordant xenografts when hyperacute rejection is prevented: analysis using adoptive and passive transfer

Hyperacute rejection of discordant xenografts occurs rapidly, precluding cellular infiltration. Thus the role of cellular rejection in discordant xenografts is debated. Using adoptive transfer of sensitized splenocytes and passive transfer of sensitized serum, we evaluated the influence of cellular and humoral elements on cellular infiltration and rejection in the guinea-pig-to-rat discordant xenograft model. Guinea-pig hearts were transplanted into Lewis rats. Pretransplant, rats underwent splenectomy and plasma exchange and were started on daily cobra venom factor injections. Xenografts rejected faster after adoptive (1, 2, 2 and 2 days) or passive (1, 1, 2 and 2 days) transfer than controls (4, 4, 4 and 4 days; p < 0.05). Macrophages and neutrophils were predominant in early prerejection specimens. Over time, cellular infiltrates were dominated by mononuclear cells. Natural killer cells were present in all groups, as were interleukin 2 receptor positive cells. Our data suggest that either sensitized serum or sensitized cells are capable of initiating an accelerated rejection characterized by cellular infiltration. Despite subtle differences, the population of infiltrating cells was similar in each group. Thus, although rejection may be initiated by either cellular or humoral influences, the ultimate result is the same. We have, therefore, established a small animal model to study cellular rejection in discordant xenografts. This model will help evaluate the role of cell subsets and xenoantibodies in xenograft rejection and will help determine the precise relationship between the two when hyperacute rejection is prevented.

Immunotherapy of murine leukemia. IX. The requirement for the Fc portion of antibody for successful passive serum therapy of Friend leukemia virus-induced disease

The possible role of an antibody-dependent cellular cytotoxicity (ADCC)-type mechanism in the passive serum therapy of Friend leukemia virus (FLV)-induced erythroleukemia has been investigated by determining whether successful serum protection requires an intact Fc portion on the administered antibody. F(ab')2 fragments of IgG extracted from chimpanzee anti-FLV and goat anti-FLV gp71 antisera were prepared and compared with whole serum and uncleaved IgG for their capacity to protect DBA/2 mice against challenge with leukemogenic dose of FLV. Despite demonstrating in vitro virus neutralizing activity equivalent to that seen with antiviral serum or IgG, the virus-specific F(ab')2 preparations were devoid of protective activity. Given that passively administered F(ab')2 of goat origin have been reported to persist at stable levels in the mouse circulation, the failure of these F(ab')2 preparations to protect against virus challenge cannot be ascribed to rapid clearance from the treated animals. These results indicate that the passive serum therapy of FLV-induced disease is Fc dependent, consistent with the involvement of an ADCC-type mechanism, as well as confirming the previous suggestion that virus neutralization does not represent the sole mechanism of serum protection in this system.

Activation of macrophages by in vitro allostimulated T cells

Murine peritoneal macrophages, parabiotically co-cultured with combinations of in vitro H-2 sensitized thymus-derived lymphocytes obtained from drug-pretreated mice, possessed an increased cytotoxicity against alloantibody-coated target cells. This heightened activity appeared to be accentuated by and dependent on T-cell synergy. After 5 days of in vitro allosensitization at 37 degrees C, cortisone-resistant thymocytes allosensitized in combination with cyclophosphamide-pretreated splenic T cells released molecules that produced strong antibody-dependent macrophage-mediated cytotoxicity (ADCC). This enhanced ADCC correlated with increased macrophage rosetting with IgG-sensitized erythrocytes. These heightened activities resulted from soluble mediators released by the activated T cells which diffused across a 0.22-microns Millipore filter and were not dependent on lymphocyte-macrophage contact. Evidence that these molecules originated from the highly enriched T-cell populations and were not synthesized de novo by macrophages was supported by results of pretreatment with protein and RNA synthesis inhibitors. Evidence that soluble Fc receptors released from the alloactivated T cells were responsible for the increased macrophage EA binding and ADCC was obtained in affinity chromatography experiments in which activity could be depleted by passage over a Sepharose-Fc-coupled column and recovered in the column eluate.

In vitro analysis of lymphocytes: markers and functions

Current dermatologic literature is becoming replete with articles elucidating current concepts in the pathophysiology of lymphocytic diseases. Much of this knowledge emanates from the increasingly sophisticated and complex methods of identifying lymphocytes. No longer does it suffice to know that B lymphocytes or T lymphocytes are present, but rather the key information involves knowing what subsets of these cells are present and/or their functional status. The reader attempting to assimilate all this information is thus confronted with an overwhelming, as well as frequently changing, array of analytic methods. This paper is presented as a review of thinking, principles, and methods employed in research on lymphocytic disease.

Cytotoxicity reactions against target cells infected with rabies virus

Some aspects of the cytotoxicity reactions were studied in the rabies system. The antibody-dependent complement cytotoxicity (ADC), the cellular cytotoxicity (CC), and the antibody-dependent cellular cytotoxicity (ADCC) are shown, being the cytotoxic effect as evidenced by the 51Cr released from the cells infected with the Pasteur strain of rabies virus. Some parameters such as time of cellular infection, the amount of infected cells, the concentration of complement, and the incubation time of the ADC reaction, which help to increase the performance of this reaction, are discussed. The detection and the level of the cellular response against the Pasteur strain of rabies virus in immunized mice is shown. Evidence is presented that in the ADCC test, specific human antibodies and non-immune human lymphoid cells are able to mediate in vitro lysis of cells infected with rabies virus. A comparison of the ADCC test with serum neutralization and immunoenzymatic tests is shown.

Failure to detect killer cell activity in rabbits

Rabbit lymphoid cells from spleen, peripheral blood, and peritoneal cavity lacked killer (K)-cell activity against cell lines of rabbit and human origin, including virus-infected human tumor cells. This lack of activity was not affected by antibody concentration, source of antibodies, effector/target cell ratio, or length of assay. Rabbit leukocytes, however, were capable of lysing antibody-coated chicken erythrocytes. Hamster leukocytes, serving as a known source of K cells, mediated antibody-dependent cellular cytotoxicity against all targets. EA-rosette assays and mixed effector cell competition tests suggested a deficiency in rabbit K-cell activity which is not a result of an inherent lack of Fc receptor-positive cells or of some suppressor mechanism operating in the rabbit cell populations. Our data support the concept that antibody-dependent cellular cytotoxicity may not be a significant in vivo immune mechanism in certain species.

Mechanisms of cell-mediated cytotoxicity in mice rejecting xenogeneic human lymphoblastoid cells

The in vivo immunization of mice with human lymphoblastoid cell line LNH13 generates direct cell-mediated cytotoxicity by spleen cells. The lytic activity appears as early as day 3 after the intraperitoneal inoculation of 7.5 x 10(6) cells and persists at least until day 11. The killer cells do not adhere to plastic and are not retained on nylon wool columns or on Degalan beads coated with mouse Ig plus rabbit-anti-mouse Ig. The effector cells are partly inhibited by treatment with anti-Thy-1.2 serum plus complement, but this inhibition appears to be non-specific since anti-serum alone or normal serum plus complement have the same effects. Heat-aggregated IgG strongly inhibits cytotoxicity, indicating that the effector cells are Fc-positive and that such receptors are implicated in lysis. Altogether, these features strongly argue for an ADCC phenomenon. The involvement of antibodies is demonstrated by the fact that eluates (56 degrees C, 30 min) from immune cells alone induce lysis in the presence of normal spleen cells as effectors. The lytic activity of these eluates can be removed by specific adsorption on protein A coupled to Sepharose beads and on the human lymphoid target cells. Positive complementation between immune and non-immune spleen cells suggest that the arming process may occur in vitro during the assay, when antibodies are released by plasmacytes.

Environmental chemical-induced modification of cell-mediated immune responses

It is therefore proposed that: 1) environmental chemicals can have specific mechanisms of toxicity and can influence antibody-mediated immunity while having no detectable effect on cell-mediated immunity, 2) immune dysfunction is related to exposure time to a chemical and the tissue concentration of that chemical, 3) recovery of immune function may occur even though chemical exposure continues, and 4) a single assay of immune function may not be appropriate to detect chemical induced immune dysfunction.

Immune response to human keratoacanthoma

Immune reactivity to human keratoacanthoma was investigated by microcytotoxicity tests and immunofluorescence. IgM and complement were consistently present in lesions; IgG and fibrin were infrequent. No evidence of in vivo bound immunoglobulin was found on the surface of keratoacanthoma cells by membrane immunofluorescence. Neither patients' sera nor peripheral blood leukocytes showed significant cytotoxicity against autochthonous tumour cells in microtitre assays. This study fails to support the view that regression of human keratoacanthoma is mediated by immunological mechanisms.

Comparison of the binding of radiolabelled human IgG and Fc fragments to murine spleen cells

The binding properties of an IgG1 human myeloma protein, normal IgG, and the Fc and Fab fragments of each were compared in cultures of murine spleen cells. Both 125I-labelled IgG and Fc fragments bound to splenic lymphocytes, whereas Fab fragments did not bind significantly at the highest concentrations tested. On a molar basis, more Fc bound than intact IgG. According to Scatchard plot analysis, the affinity constand of IgG1 was 1.5 x 10(6) +/- 1 x 10(5) L/M and that of the Fc fragments was 7.8 x 10(5) +/- 2.6 x 10(5) L/M. Approximately 25,000 binding sites/cell were calculated for IgG1 and 102,000 for Fc. Deaggregation of the Fc preparation did not change these values, suggesting that the difference in binding of IgG and Fc did not result from Fc aggregation. Unlabelled IgG inhibited about 25% of the labelled Fc binding, whereas unlabelled Fc inhibited approximately 80% of the labelled Fc binding. IgG antigen-antibody complexes, however, inhibited 75% of the Fc binding. In the reciprocal experiment both intact IgG and Fc inhibited the binding of labelled IgG by 100%. The major cell population that bound IgG and Fc fragments in the spleen cell preparation were the B lymphocytes. Removal of macrophages did not significantly affect the binding of labelled Fc fragments. In addition, T-cell-enriched populations bound an insignificant quantity of Fc fragments.

The characterization and functional significance of plasma membrane Fc Receptors

The importance of various components of the plasma membrane in the generation of the immune response has long been recognized. The identification and characterization of functional membrane receptors are essential for an understanding of the molecular basis of the immune response. The Fc receptor can be operationally defined as a site on the plasma membrane which is capable of binding the Fc portion of IgG. The Fc receptor has been reported on both lymphoid and nonlymphoid cell types. The functional significance of the receptor on these cell populations, as well as the biochemistry of the receptor, is not well established and is currently an important area of investigation. In this review, the Fc receptor will be discussed, primarily in human and murine lymphoid and macrophage cell populations, as a model of membrane immunoreceptors. The review will be divided into four sections. In the first section, consideration will be given to the binding assays used to study Fc receptor-ligand interactions and the class and subclass specificity of the receptor. The possibility of receptor-receptor interaction and quantitation of receptor sites will be discussed. The second phase of the review will be concerned with the fractionation and biochemistry of this receptor system, emphasizing the differences reported in receptor composition from different cell sources. In the third section of the review, the biologic significance of the receptor will be examined. The importance of the Fc receptor in opsonization and phagocytosis by mononuclear phagogytes, B-cell activation, antibody-dependent cell cytotoxicity, and the possible relationship of Fc receptors to the histocompatibility-linked immune response genes will be discussed. Finally, in the fourth section, the possible mechanisms of receptor regulation will be considered. Cell fusion experiments which have been performed and the expression of receptor activity on the hybrid cell clones will be discussed. Receptor regulation at the physiologic level will include the effects of cyclic nucleotide levels and cell cycle on receptor expression. It is the intent of this review to provide a detailed analysis of the Fc receptor and to emphasize its importance in microbiology, cell biology, and immunology.

Heterogeneity among human lymphocyte effector cells mediating spontaneous lymphocyte-mediated cytotoxicity

The spontaneous lymphocyte-mediated cytotoxicity (SLMC) of lymphocytes from normal individuals was studied using the lymphocyte titration assay. Various techniques were used to study selectively several lymphocyte subpopulations. The activity of these subpopulations was tested in both the antibody-dependent cellular cytotoxicity (ADCC) and lymphocyte titration assays. Surface marker studies were performed on each lymphocyte subpopulation. The results from these studies indicate that effector cells mediating SLMC are a heterogeneous lymphocyte population composed of Fc-receptor-positive lymphocytes both with and without C3 receptors that consistently segregate with cells that do not form rosettes with sheep red blood cells. Our data suggest that, in many respects, the effector cells in SLMC and ADCC are identical. However, the mechanism appears to be different.

K-lymphocytes (killer-cells) in Crohn's disease and acute virus B-hepatitis

Total lymphocyte counts, B-, T-, C'3 receptor-bearing lymphocytes, and K-cell activity were studied in peripheral blood in patients with Crohn's disease and inflammatory liver disease. Patients with active untreated Crohn's disease and acute virus B hepatitis exhibited a markedly increased K-cell activity measured in a plaque assay when compared with normal controls (P less than 0.01). Patients with immunosuppressive treated Crohn's disease, HBsAg-positive chronic active hepatitis, and cirrhosis of the liver showed only a slight increase of K-cell activity (P less than 0.01). In the postacute phase of hepatitis (four to 12 weeks from onset) K-cell activity fell to normal levels. The number of B-lymphocytes showed a relative and absolute decrease in all groups of patients. With the exception of patients with acute HBsAg-positive hepatitis and the post-acute phase of hepatitis all the other groups showed statistically decreased absolute numbers for C'3 receptor-bearing lymphocytes. The significant decrease in K-cell activity and the number of T-lymphocytes in Crohn's disease treated with immunosuppressive drugs was interpreted as an effect of azathioprine and prednisone on these lymphocyte subpopulations.

Antibody-dependent cell-mediated cytotoxicity in treated and nontreated cancer patients

Antibody-dependent cell-mediated cytotoxicity (ADCC) exhibited by peripheral blood leukocytes was used as a criterion for assessing immune competence of groups of noncancerous individuals and of treated and untreated cancer patients. The results show that, as a group, leukocytes of nontreated cancer patients exhibited significantly lower ADCC than that exhibited by leukocytes of noncancerous individuals. However, the ADCC of leukocytes from cancer patients under treatment approximated that of normals. Thus, using ADCC as criterion, the results indicate that as a group, cancer patients under treatment tend to exhibit restored immune competence.

The mechanism of K cell (antibody-dependent) cell mediated cytotoxicity. I. The release of different cell components

The release of different cell components during K cell (antibody-dependent) cytotoxicity of P815 mastocytoma cells by rat spleen cells has been studied. The release of the small molecules chromium-51 and phosphoryl choline follow the same time course as the release of macromolecular protein and RNA, suggesting a sudden rupture of the cytoplasmic membrane. These components are rapidly released over the first 15–30 min whereas in T cell cytotoxicity the rate of release is approximately linear with time (Sanderson 1976 a ). This suggests that cell death occurs more rapidly after K cell than after T cell contact. Nicotinamide and rubidium-86 are released more rapidly than these other components but release does not continue after 15–30 min. The release of these two components may be mainly a result of K cell contact and some K cell contacts may not progress to target cell death. The release of DNA shows a 30–45 min lag suggesting that the nuclear rupture is secondary to cytoplasmic rupture.

Immune complexes in hepatitis B antigen-associated periarteritis nodosa. Detection by antibody-dependent cell-mediated cytotoxicity and the Raji cell assay

A subpopulation of peripheral blood lymphocytes with the ability to lyse target cells coated with specific antibody (antibody-dependent cell-mediated cytotoxicity, ADCC) was serially studied in a patient with hepatitis B antigen-associated periarteritis nodosa. The effector lymphocytes possess FC and complement receptors but do not require complement for functional activity. We found that the patient's ADCC was decreased during periods of disease activity and was almost normal during remission. The patient's serum could block ADCC in normal lymphocytes, and the blocking ability correlated with the concentration of immune complexes as determined by the Raji cell assay (a radioimmunoassay using complement receptors on human cultured lymphoblastoid cells). The concentration of immune complexes and the ADCC blocking ability of ther serum both correlated with disease activity. Serum from five other patients with active vasculitis was found to contain significant amounts of immune complexes and was able to block normal ADCC. It appears that the ADCC assay can be used to detect the presence of circulating immune complexes and to monitor disease activity in periarteritis nodosa.

Nature of the effector cells responsible for antibody-dependent cell-mediated killing of Cryptococcus neoformans

Studies were performed to identify the types of human peripheral blood leukocytes capable of killing Cryptococcus neoformans in the presence of anticryptococcal antibody in vitro. A total of 24.1 +/- 2.7% (mean +/- standard error of the mean of four experiments) of the original cryptococcal inoculum survived in a mixed mononuclear, cell preparation (approximately 30% monocytes) after 4 h of incubation at 37 degrees C with rabbit anticryptococcal antibody. When phagocytic cells were removed, there was 36.4 +/- 4.6% survival in six experiments, compared with 52.8% survival in the presence of purified granulocytes (mean of two experiments) and 96.9 +/- 1% survival in the presence of purified T cells. There was never any significant killing in control mixtures that contained leukocytes with normal rabbit serum nor in those that contained anticryptococcal antibody without effector leukocytes. Significant antibody-dependent fungicidal activity was seen with ratios of effector to target cells as low as 6.25:1. These observations indicate that multiple types of peripheral blood leukocytes, excluding T cells, are capable of antibody-dependent fungicidal activity.

The local immune response to Escherichia coli O and K antigen in experimental pyelonephritis

Although the systemic and local immune response to the O antigen of Escherichia coli has been well characterized, little information is available on the immune response to K anigen. Experimental hematogenous pyelonephritis was produced with Escherichia coli 06 K13 H1 and the serum and local (intrarenal) antibody response to O and K antigens was determined with the enzyme-linked immunosorbent assay. Both local and serum antibody responses to the K antigen were significantly less than that to the O antigen. The K antigen induced low titer IgM and IgG antibody responses in fewer than one-half of the animals and did not induce a local IgA response in any animal. In contrast, the O antigen induced local antibody responses in each of the immunoglobulin classes in all animals from day 9 of infection. Similarly, the serum IgM and IgG antibody titers to the K antigen were significantly less than those evoked in response to the O component of the Escherichia coli. No serum IgA anti-K antibodies were detected. These observations helf clarify the roles of these two antigens in pyelonephritis. Although the K antigen of Escherichia coli functions as a virulence factor in upper urinary tract infections, this antigen does not elicit a significant immune response, whereas the O antigen does induce a significant antibody response which could be of protective or diagnostic benefit.

Antibody-dependent cell-mediated cytotoxicity in cows: comparison of effector cell activity against heterologous erthrocyte and herpesvirus-infected bovine target cells

Bovine peripheral blood leukocytes (PBL) and cells collected from the bovine mammary gland were assayed for antibody-dependent cell-mediated cytotoxicity (ADCC) against chicken erythrocyte (CRBC) and bovine herpesvirus-infected bovine kidney cell targets. Bovine antisera were used to sensitize target cells. Both PBL and mammary leukocytes expressed ADCC, with the latter cell population having greater activity against both target cells. Only the CRBC target cells were killed by nonadherent PBL and phagocyte-depleted PBL. Nonadherent mammary leukocytes, rich in monocytes and macrophages, did kill virus-infected target cells. Carbonyl iron-treated mammary leukocytes failed to kill virus-infected targets but could destroy CRBC targets. Antimacrophage serum inhibited lysis of both CRBC and virus-infected targets, but antilymphocyte serum only inhibited CRBC killing. These observations indicated that at least two kinds of cells could mediate ADCC against CRBC but only cells of the mononuclear phagocytic series could kill virus-infected target cells. The herpesvirus-infected target cells became susceptible to ADCC 9 h after virus infection. A case is made for investigating the phenomenon of ADCC using in vitro systems that closely mimic the in vivo situation. The possible role of the ADCC mechanism as instrumental in causing recovery from herpesvirus infections is discussed.

Human tumor cells grown in fetal calf serum and human serum: influences on the tests for lymphocyte cytotoxicity, serum blocking and serum arming effects

Peripheral blood lymphoid cells (PBL) from cancer patients and normal donors were tested against three melanoma cell lines grown in either 10% fetal calf serum (FCS) or 2.5-5% human AB serum in order to determine if the heterologous membrane (HM) antigen or other FCS antigens acquired from the bovine serum supplement could influence lymphoid cell-mediated cytotoxicity in vitro. FCS-grown melanoma cells were more susceptible than the AB serum-grown subline to lymphocyte cytotoxic effects. Arming effects by autologous sera on normal donor lymphocytes and to a lesser extent on lymphocytes of cancer patients were more pronounced on the FCS-grown M12 melanoma cells. This effect was abrogated when the cells were grown in human AB serum for at least 8 weeks. The non-HM tumor-associated antigen remained at the same original low level. Blocking effects were more evident on the AB-grown M14 melanoma line. These data suggest that the FCS antigens on the cell surface may have been responsible for the augmented PBL cytotoxicity. The anti-FCS antibody present in normal and cancer patients' blood induced an antibody-dependent cellular cytotoxicity (ADCC). Elimination of arming activity against HM or other FCS antigens from AB-grown cells may have made the serum blocking factors more apparent. However, cytotoxicity against tumor cells by PBL from normal donors was still apparent even on the human serum-grown cells, suggesting that a different antigen-antibody system was also responsible for this "non-specific" activity.

Antibody-dependent cell cytoxicity (ADCC). Characterization of 'killer' cells in human lymphoid organs

The effector cell(s) in human antibody-dependent cell cytotoxicity (ADCC), with antibody-coated chickens erythrocytes as targets, was studied by comparison of cell suspensions from various lymphoid organs and by means of various cell fractionation methods. Effector cells (K) were found mostly in peripheral blood, spleen, and bone marrow but not in tonsils, lymph nodes, and thymus. Effector cells bear Fc receptors and can form EA rosettes with the antibody-coated target cells. About 1,5% peripheral blood lymphocytes can form 'high-avidity' EA rosettes with targets coated at low antiserum concentration. Most of the effector cells belong to this small subset, as shown by experiments of selective depletion. Removal of most monocytes, T cells, or B cells from, or addition of T-cell-specific antiserum to, the effector cell suspensions did not affect ADCC. Effector cells in this model of ADCC therefore lack the conventional B- or T-cell markers but at least some of them are likely to bear C3 receptors.

The lethal hit stage of mouse T and non-T cell-mediated cytolysis: differences in cation requirements and characterization of an analytical "cation pulse" method

We investigated in detail the cation requirements of two different systems of mouse cell-mediated cytolysis in vitro, at their recognition, post-recognition hit and target cell disintegration stages. In T cell-mediated cytolysis, respectively Mg++ or Ca++, Ca++, and no cations, were required. In non-T cell-mediated hemolysis, respectively no cations, Mg++, and no cations, were required. Two main conclusions can be drawn. First, the cation requirements are different from one system to the other especially at the post-recognition hit stage, which strongly suggests the existence of differences between both systems as to the actual mechanism of lysis. Second, the cation requirements are different within each system from one step to another. This formed the basis of a step-by-step analysis of the lytic process, leading to the characterization of a cation pulse method for the experimental isolation and further study of the post-recognition hit stage of cell-mediated cytolysis.