Antibody-dependent cellular cytotoxicity in chronic human Chagas disease

Antibody-dependent cellular cytotoxicity mediated by granulocytes (ADGC) or lymphocytes (ADLC) was assessed in 23 patients with chronic Chagas disease. The results of ADGC against T. cruzi were normal. ADLC against chicken erythrocytes was significantly reduced in patients as compared with normal controls. Possible causes of this abnormality were investigated.     

Antibody-dependent cell-mediated cytotoxicity against influenza virus-infected cells

The three major immunocompetent cells in human peripheral blood (lymphocytes, neutrophils, and monocytes) were shown to be effector cells for antibody-dependent cell-mediated cytotoxicity (ADCC) against influenza virus-infected baby hamster kidney cells in vitro. Lymphocyte cytotoxicity was mediated by FcIgG receptor-bearing null cells and T gamma cells. These effector populations were best defined by HNK-1, a monoclonal antibody to human natural killer and ADCC-mediator cells. Antibody responsible for ADCC against influenza virus-infected cells was detectable in sera of young children after natural infection and after vaccination with inactivated and live attenuated viruses. ADCC antibody appeared before hemagglutination-inhibiting antibody and persisted for at least one year after vaccination with live attenuated vaccine. ADCC antibody was subtype-specific but quite broadly reactive within a subtype. Both hemagglutinin and neuraminidase were antigenic determinants for ADCC antibody. An anamnestic response to the original strain was observed after challenge with influenza virus of a heterologous subtype.     

The effects of in vivo hydrocortisone on lymphocyte-mediated cytotoxicity

To examine the effects of in vivo hydrocortisone sodium succinate (HC) on natural killer (NK) cell and antibody-dependent cellular cytotoxicity (ADCC), 11 normal adults received a single intravenous bolus of 400 mg hydrocortisone. Lymphocytes were tested for NK activity and ADCC using 51chromium (51Cr)-release and single cell cytotoxicity assays against Molt-4 and sensitized RL O leads to target cells, respectively. Four hours after injection, both NK and ADCC activity were transiently increased in the 51Cr-release system (P less than 0.05). At 4 hours, there was a twofold increase in the relative frequency of potentially cytotoxic target binding cells (P less than 0.001) but the absolute number of these cells did not change (P less than 0.1). However, the percentage lysis of bound targets at 4 hours was not altered (P greater than 0.1). These data suggest that: 1) lymphocytes participating in NK and ADCC reactions are refractory to the kinetic and functional effects of HC; 2) the increased lytic activity observed at 4 hours is due to a selective depletion of noncytotoxic cells from the circulation; and 3) NK and ADCC activity did not differ in their responses to HC.     

Antibody-dependent and PHA-induced cellular cytotoxicity in rheumatoid arthritis.

One hundred and thirty nine observations of antibody-dependent cell mediated cytotoxicity (ADCC) were made on 77 with rheumatoid arthritis (RA) and 17 healthy controls. There were no differences in ADCC between these 2 groups or within the RA group with regard to disease activity, duration, seropositivity, or drug treatment. Sixty observations of phytohaemagglutinin induced cytotoxicity were made on 22 patients with RA and 10 healthy controls. Again there were no differences in cytotoxicity between the 2 groups.     

Antibody-dependent and natural killer cytotoxicity in type 1 diabetes

Summary The antibody-dependent cell-mediated cytotoxicity and the spontaneous cell-mediated cytotoxicity against Chang liver cells in relation to the levels of circulating K-cells (low affinity E-rosetting cells) were investigated in 23 newly diagnosed insulin-dependent (Type 1) diabetics, and in 17 unaffected islet cell antibody-positive subjects. Antibody-dependent cell-mediated cytotoxicity was significantly increased in those newly diagnosed diabetics with K-cell levels greater than 2 SD above the mean of normal controls (p<0.02). A similar but not significant trend was also found in islet cell antibody-positive subjects with raised K-cells. Spontaneous cell-mediated cytotoxicity was not different in any of the groups. These results lend further support to the concept that antibody-dependent lymphocyte cytotoxicity is enhanced in Type 1 diabetes at diagnosis.     

Arf6: a new player in FcgammaRIIIA lymphocyte-mediated cytotoxicity

The activation of phosphoinositide metabolism represents a critical step in the signaling pathways leading to the activation of cytolytic machinery, but its regulation is partially understood. We report here that the stimulation of the low-affinity receptor for immunoglobulin G (IgG) (FcgammaRIIIA, CD16) on primary human natural killer (NK) cells induces a phosphatidylinositol 3-kinase (PI3K)-dependent activation of the small G protein Arf6. We first demonstrate a functional role for Arf6-dependent signals in the activation of the antibody-dependent cellular cytotoxicity (ADCC) attributable to the control of secretion of lytic granule content. We also show that Arf6 couples CD16 to the lipid-modifying enzymes phosphatidylinositol4phosphate 5-kinase type I alpha (PI5KIalpha) and phospholipase D (PLD) that are involved in the control of granule secretion; Arf6, but not Rho family small G proteins RhoA and Rac1, is required for receptor-induced PI5KIalpha membrane targeting as well as for PI5KIalpha and PLD activation. Our findings suggest that Arf6 plays a crucial role in the generation of a phosphatidylinositol4,5-bisphosphate (PIP2) plasma membrane pool required for cytolytic granule-mediated target cell killing.     

Antibody-dependent and phytohaemagglutinin-induced lymphocyte cytotoxicity in systemic lupus erythematosus.

An investigation of cell-mediated cytotoxicity in 22 patients with systemic lupus erythematosus (SLE), using both whole blood and purified peripheral blood mononuclear cells (PBM) to measure antibody-dependent (ADCC) and phytohaemagglutinin (PHA)-induced lymphocyte cytotoxicity for Chang liver cells, has revealed 2 distinct abnormalities in patients with active disease. PHA-induced cytotoxicity was found to be selectively reduced in whole blood assays only (P less than 0.05), whereas ADCC was impaired in both whole blood (P = 0.02) and PBM (P less than 0.05) assays, when comparison was made with 52 normal controls. The addition of patients' sera to corresponding assays utilizing control PBM confirmed that the impaired PHA-induced cytotoxicity resulted from circulating inhibitory serum factors. Surprisingly little effect, however, was exerted on ADCC assays. These findings suggest that there is a reduction in numbers and/or functional capacity of Fc-receptor cells in active SLE, which may have pathogenetic implications.     

Antibody-dependent cellular cytotoxicity against HIV-1 in sera of immunized chimpanzees

After immunization of chimpanzees against HIV antigens, antibodies that mediate antibody-dependent cellular cytotoxicity (ADCC) were evaluated and compared with anti-HIV-antibody levels detected by enzyme-linked immunosorbent assay (ELISA) and neutralizing antibody titers. Adult chimpanzees were immunized with different HIV-1 (LAV-BRU) antigen preparations: recombinant vaccinia virus (rVV) expressing gp160, p25 or p27nef; formalin- and beta-propiolactone-inactivated whole virus (inHIV); soluble recombinant gp160 either associated or not associated with other HIV proteins; a 25-mer peptide from the V3 region of gp120 coupled with KLH (V3-KLH). Immunization with the various rVV mixtures induced no or borderline ADCC increase above preimmune serum levels. Stronger and more sustained reactivity was elicited by inHIV. Purified HIV antigens elicited ADCC activity when the chimpanzees were naive; ADCC increased or remained at the same level when the animals had been preimmunized with rVV and/or inHIV. This type of reactivity apparently did not depend on whether gp160 alone or mixed with other proteins was used for immunization. The injection of V3-KLH resulted in only little, if any, recall ADCC response. ELISA antibody titers significantly correlated with ADCC and neutralizing antibody titers, but serum ADCC was independent of neutralizing antibody titers, an indication that the two latter serum activities are mediated by independent antibodies. Therefore, ADCC is elicited in the same manner as other antibody activities by the immunization of chimpanzees with inHIV or with purified recombinant HIV antigen preparations. The results obtained from the three chimpanzees of this series, which were subsequently challenged with infectious virus through the intravenous route, suggest that serum ADCC may be considered for vaccination purposes.     

Antibody-dependent cell-mediated cytotoxicity against cells infected with the human immunodeficiency virus

Human immunodeficiency virus (HIV) elicits the production of virus-specific antibodies in infected individuals. We investigated the ability of serum from HIV-infected individuals to mediate antibody-dependent cellular cytotoxicity in an in vitro 51Cr release assay system. Fresh peripheral blood mononuclear cells from healthy donors seronegative for HIV were used as cellular effectors against HIV-infected and uninfected H9 target cells in the presence of serum from HIV-infected or uninfected donors. Serum from HIV-infected, but not uninfected, donors significantly augmented cytolysis of virus-infected targets (P less than .005). There was no augmented killing of uninfected H9 cells with sera from either group. Studies using serum from mice that had been immunized with synthetic peptides from the HIV envelope region suggested that this response is directed, at least in part, at several determinants of the transmembrane portion of the HIV envelope glycoprotein.     

Antibody-dependent cell-mediated cytotoxicity against cell lines generated by liver-specific idiotype-bearing antibody

We produced a murine monoclonal antibody (mAb), designated H2-mAb, against a fractionated soluble phase of human liver homogenate which antibody reacted with human liver cells. A human antibody possessing the same idiotype as the H2-mAb, designated LSIA (liver-specific idiotype-bearing antibody), can be measured by a sandwich enzyme-linked immunosorbent assay, using the anti-H2 idiotype antibody. The serum level of LSIA in patients with histologically proven chronic hepatitis (CH) was significantly higher than that in healthy subjects and it was also higher than that in subjects with other diseases, including systemic lupus erythematosus. In a comparison between patients with CH type B and those with CH type C, there was no significant difference in serum levels of LSIA. It was possible to purify LSIA from the sera of patients with CH. The purified LSIA bound to the human cell lines Chang and HCC-M, derived from liver cells and a hepatoma respectively, but not to HeLa cells, a uterine carcinoma derivative. The reactivity of this mAb to HCC-M was weaker than that to Change. Moreover, the presence of LSIA caused an antibody-dependent cell-mediated cytotoxic challenge against Change cells in vitro.     

Antibody-dependent cell-mediated cytotoxicity: comparison between HTLV-I and HIV-1 assays

This study confirms the presence of detectable antibody-dependent cell-mediated cytotoxicity (ADCC) towards both HTLV-I- and HIV-1-infected cell lines, mediated by normal donor peripheral blood mononuclear cells and either by antibody from adult T-cell lymphoma and tropical spastic paraparesis patients (HTLV-I) or by antibody from sera of patients with persistent generalized lymphadenopathy, AIDS-related complex, AIDS and asymptomatic patients seropositive for HIV-1 infection. A comparison of ADCC towards these two retroviruses, under carefully controlled laboratory conditions, indicates major differences between the capacity of HTLV-I-seropositive sera and HIV-1-seropositive sera to mediate ADCC. In all cases, HIV sera showed low-titre ADCC, in contrast to the high titre (greater than 1:800,000) ADCC mediated by HTLV-I-positive sera. Both sets of sera showed the prozone phenomenon, and heat inactivation may abolish ADCC towards HIV-1-infected cells. Quantitation of surface antigen expression on HTLV-I- and HIV-1-infected cell lines indicated the presence of easily detectable amounts of virus-specific antigen. We conclude that, in contrast to some previous reports, ADCC mediated by HIV-1-specific immunoglobulin G (IgG) antibody is rather weak and of low titre when compared with HTLV-I ADCC. This is true for all cell lines and HIV-1 virus isolate combinations tested.     

Antibody-dependent cell-mediated cytotoxicity and phagocytosis of autologous red blood cells in alphamethyldopa-induced haemolysis

7 alphamethyldopa (AMD)-treated patients with positive direct antiglobulin test (DAT) were investigated. Peripheral blood mononuclear phagocytes of 2 patients suffering from haemolysis caused lysis and phagocytosis of autologous DAT-positive red blood cells (RBC). Eluates from RBC of both patients contained antibodies of IgG1 subclass and supported antibody-dependent cell-mediated cytotoxicity (ADCC) and antibody-dependent phagocytosis (ADPh) of the patients' RBC after remission. Both cytotoxic activities were proportional to the serum concentration and to the number of attacking cells. The 5 patients without overt haemolysis did not show in vitro lysis or phagocytosis of autologous RBC. These results suggest that ADCC as well as ADPh participate in the destruction of RBC in AMD-induced haemolysis in vivo.     

In vitro morphological studies on antibody-dependent nonimmune lymphocyte-mediated cytotoxicity in chronic active liver disease

Using anin vitro system of antibody-dependent cellular cytotoxicity (ADCC), the killing effect of chronic liver disease sera on target Chang cells, mediated by effector nonimmune lymphocytes (NLy), was studied. NLy destroyed Chang cells in monolayers pretreated with sera of patients with chronic active liver disease (CALD). Sera from these patients with CALD, after receiving steroid therapy, demonstrated a significant decrease of the cytotoxic action of NLy. The target cells treated with sera of normal subjects or patients with chronic persistent hepatitis were only minimally affected. Morphological observations of the cytotoxic action in a CALD serum-treated group showed intimate contact between NLy and the target cells in the areas of the plaques, where large numbers of the target Chang cells were injured and were closely associated with effector NLy. The Chang cells developed cytoplasmic swelling. The surface became ruffled, and intracytoplasmic organelles displayed vesicular degeneration. Thereafter, cell rupture and fragmentation occurred. The sera in patients with CALD appear to possess a membrane reactive factor, presumably antibody, against the surface membrane of Chang cells. This immunological mode of reaction between the effectors and target cells (ADCC) may be important in the perpetuation and pathogenesis of hepatocyte death in CALD.Supported by Veterans Administration Hospital Research Fund.     

Antibody-dependent cell cytotoxicity against Trypanosoma cruzi is only mediated by protective antibodies

The antibody-dependent cell cytotoxicity (ADCC) to Trypanosoma cruzi blood forms (Btry) using non-adherent spleen cells is only mediated by sera from chronic chagasic patients or mice. Both display 'lytic antibodies' (LA), which are immunoglobulins directed against epitopes only present in living BTry, and 'conventional serology antibodies' (CSA), which are responsible for the positive diagnostic tests in Chagas disease. Sera from mice immunized with different T. cruzi antigens or from treated patients (displaying only CSA but not LA) are unable to mediate ADCC. These data confirm the central role played by LA in the host resistance against T. cruzi. Moreover, they probably explain why most immunizing agents used as vaccines in Chagas' disease and which elicit CSA but not LA, do not display significant protection against T. cruzi. We also demonstrate that trypsinization of BTry increases significantly the rate of parasite destruction by ADCC, suggesting that enzyme sensitive membrane components may help BTry to evade from this immune effector mechanism.     

Antibody-dependent cellular cytotoxicity independently predicts survival in severely immunocompromised human immunodeficiency virus-infected patients.

The exact immune defects leading to human immunodeficiency virus (HIV)-associated opportunistic infections, malignancies, and death are unknown. In this study, the relationship between survival and 2 immune functions, cytomegalovirus-specific antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activity, was determined by using peripheral blood mononuclear cells from 39 severely immunocompromised patients (median CD4 count, 7). Median follow-up was 414 days; 15 subjects died and 24 remained alive. In a Kaplan-Meier analysis, high baseline ADCC (>median) was associated with improved survival (P=.05). A similar trend was observed for NK activity (P=.1). In a multivariate model controlling for baseline CD4 cell count, HIV RNA, and use of protease inhibitors during follow-up, high ADCC, but not high NK activity, remained significantly associated with a lower risk of death (relative risk, 0.18; 95% confidence interval, 0.05-0.75). ADCC may be an important determinant of disease progression independently of anti-retroviral therapy, CD4 cell count, and HIV RNA.     

Antibody-dependent cytotoxicity of Trypanosoma cruzi antigen-coated mouse cell lines by eosinophils and neutrophils

Eosinophils and neutrophils are shown to be cytotoxic against two syngeneic mouse cell lines cells when these are coated with T. cruzi antigen and anti-T. cruzi antibody. Activity is detected within 5 h of incubation. Highest levels of cytotoxicity are obtained at antibody dilutions of 1:100 and 1:1000, while antiserum at 1:10 is shown to be inhibitory. Eosinophils show significant activity at an effector to target ratio of 5:1. No cytotoxicity occurs in the absence of either antigen, antibody or effector cells. This phenomenon may be a model for the tissue destruction in acute T. cruzi infection, where the lysis of trypanosomes may lead to antigen coating of host cells, followed by antibody-dependent granulocyte-mediated cytotoxicity of the host cells.