Lymphoid cell dependent (K-cell) lysis of human erythrocytes sensitized with Rhesus alloantibodies

Pathogenesis and mechanisms of antibody-mediated hemolysis

BACKGROUND

The clinical consequences of antibodies to red blood cells (RBCs) have been studied for a century. Most clinically relevant antibodies can be detected by sensitive in vitro assays. Several mechanisms of antibody-mediated hemolysis are well understood. Such hemolysis after transfusion is reliably avoided in a donor-recipient pair, if one individual is negative for the cognate antigen to which the other has the antibody.

STUDY DESIGN AND RESULTS

Mechanisms of antibody-mediated hemolysis were reviewed based on a presentation at the Strategies to Address Hemolytic Complications of Immune Globulin Infusions Workshop addressing intravenous immunoglobulin (IVIG) and ABO antibodies. The presented topics included the rates of intravascular and extravascular hemolysis; immunoglobulin (Ig)M and IgG isoagglutinins; auto- and alloantibodies; antibody specificity; A, B, A,B, and A1 antigens; A1 versus A2 phenotypes; monocytes-macrophages, other immune cells, and complement; monocyte monolayer assay; antibody-dependent cell-mediated cytotoxicity; and transfusion reactions due to ABO and other antibodies.

CONCLUSION

Several clinically relevant questions remained unresolved, and diagnostic tools were lacking to routinely and reliably predict the clinical consequences of RBC antibodies. Most hemolytic transfusion reactions associated with IVIG were due to ABO antibodies. Reducing the titers of such antibodies in IVIG may lower the frequency of this kind of adverse event. The only way to stop these events is to have no anti-A or anti-B in the IVIG products.

Efficacy of RhD monoclonal antibodies in clinical trials as replacement therapy for prophylactic anti-D immunoglobulin: more questions than answers

Prophylactic anti-D is a very safe and effective therapy for the suppression of D-immunization and prevention of haemolytic disease of the foetus and newborn. The primary mode of action of anti-D is rapid clearance of fetal D-positive red cells from the maternal circulation, mediated by interactions with immunoglobulin G Fc receptors on macrophages in the spleen. Many anti-D monoclonal antibodies (mAb) have been produced by a variety of methods. Twelve anti-D mAbs were tested in eight studies for their ability to mediate clearance of autologous red cells, and 13 antibodies studied in seven trials of the clearance of D-positive red cells injected into D-negative subjects. Antibodies produced by human B-cell lines, mouse-human heterohybridomas and Chinese hamster ovary cells varied in their activity with none being quite as effective as polyclonal anti-D. However, clearance mediated by recombinant anti-D produced by rat YB2/0 cells was extremely rapid, faster than polyclonal anti-D, but with haemolysis and some hepatic accumulation of red cells observed in one study. Two human anti-D mAbs prevented D-immunization. In contrast, anti-D mAbs from heterohybridomas increased the incidence and rapidity of anti-D responses. It is hypothesised that unnatural glycosylation of monoclonal anti-D produced by some cell lines may have caused these unexpected results. In some antibodies, unusual oligosaccharides on anti-D may have affected binding to Fc receptors resulting in reduced red cell clearance. For others, non-human glycoforms of anti-D might have bound to innate immune recognition molecules promoting pro-inflammatory reactions. These extensive data on the clinical activity of monoclonal anti-D produced by cell lines derived from four species will inform the future development of monoclonal anti-D for RhD prophylaxis.

Section 1C: Assessment of the functional activity and IgG Fc receptor utilisation of 64 IgG Rh monoclonal antibodies. Coordinator's report

Sixty-four IgG Rh monoclonal antibodies (Mabs) submitted to the Fourth International Workshop on Monoclonal Antibodies Against Human Red Blood Cells and Related Antigens were characterised and tested in quantitative functional assays at five laboratories. The biological assays measured the ability of anti-D to mediate phagocytosis or extracellular lysis of RBC by IgG Fc receptor (Fc gamma R)-bearing effector cells. Interactions of RBC pre-sensitised with anti-D (EA-IgG) with monocytes in chemiluminescence (CL) assays were found proportional to the amount of IgG anti-D on the RBC. Using antibodies to inhibit Fc gamma RI, Fc gamma RII or Fc gamma RIII, the only receptor utilised in the monocyte CL and ADCC assays for interactions with EA-IgG1 was found to be Fc gamma RI. In these assays, enhanced interactions were promoted by EA-IgG3 and additional Fc gamma receptors may have contributed. IgG2 anti-D was not reactive in these assays and EA-IgG4 promoted weak reactions through Fc gamma RI. A macrophage ADCC assay showed that haemolysis of EA-IgG3 was greater than that of EA-IgG1, mediated mainly through Fc gamma RIII. In ADCC assays using lymphocytes (NK cells) as effector cells and papainised RBC target cells, only a minority of IgG1 anti-D Mabs were shown to be able to mediate haemolysis in the presence of monomeric IgG (AB serum or IVIg). These interactions were mediated solely through Fc gamma RIII. Haemolysis via Fc gamma RIII may depend on the presence of certain sugars on the oligosaccharide moiety of IgG. Most Mabs (IgG1, IgG2, IgG3 and IgG4) elicited intermediate, low or no haemolysis in these assays. Blocking studies indicated that low activity IgG1 and IgG4 anti-D utilised only Fc gamma RI. Other IgG1 and IgG3 Mabs appeared to promote haemolysis through Fc gamma RI and Fc gamma RIII while IgG2 was inhibited by Mabs to both Fc gamma RII and Fc gamma RIII, suggesting a variety of Fc gamma R are utilised for anti-D of low haemolytic activity. Excellent agreement between the results of the lymphocyte ADCC assays and antibody quantitation was observed between the participating laboratories.

Effects of mycotoxins on human immune functions in vitro

Immunosuppressive and carcinogenic Fusarium mycotoxins may appear in domestic food products. Therefore, the immunological effects of Fusarium mycotoxins were tested on human peripheral blood mononuclear cells from different blood donors. In the present study we investigated deoxynivalenol (DON), 3-acetyldeoxynivalenol, fusarenon-X, T-2 toxin, zearalenone, alpha-zearalenol, beta-zearalenol and nivalenol for their effects on T and B cells in a proliferation assay, antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) cell activity on human peripheral blood mononuclear cells. The concentrations applied in our experiments were similar to those which can be found in normal human peripheral blood system (0.2--1800 ng/ml). Among the eight mycotoxins tested, T-2 toxin, fusarenon X, nivalenol and deoxynivalenol exerted the highest immunosuppressing effect on human peripheral blood mononuclear cells in vitro. Mycotoxin-induced immunosupression was manifested as depressed T or B lymphocyte activity. Furthermore, by virtue of inhibition of NK cell activity, the protection against tumor development may also be attenuated.

Antibody-dependent cell-mediated cytotoxicity to gliadin-coated cells with sera from children with coeliac disease

Antibody-dependent cell-mediated cytotoxicity (ADCC) has been suggested as a contributing immunological mechanism in the disease process of coeliac disease. In the present study, sera from coeliac children were examined for their capacity to mediate ADCC against gliadin-coated target cells. The ADCC-mediating efficacy of sera were tested using monocytes from healthy adults as effector cells and gliadin-coated erythrocytes from the same donor as targets. Using monocytes as effector cells, sera from children with active coeliac disease (untreated or challenged), demonstrated significantly higher ADCC-mediating capacity than sera from healthy and disease references as well as children with treated coeliac disease. A positive correlation was found between the ADCC-mediating capacity and serum IgG as well as IgA anti-gliadin antibody levels. The results suggest that an antibody-dependent monocyte/macrophage-induced cytotoxic reaction might be involved in the disease process of coeliac disease.

In vitro functional activity of IgG1 and IgG3 polyclonal and monoclonal anti-D

BACKGROUND AND OBJECTIVES

IgG anti-D is generally restricted to IgG1 and IgG3; it mediates red cell destruction through interactions with IgG Fc receptors (Fc gamma R) on effector cells. The relative ability of these two IgG subclasses of anti-D to mediate haemolysis in vitro by monocytes and K cells was investigated.

MATERIALS AND METHODS

Anti-D was affinity purified from 5 preparations of prophylactic anti-D immunoglobulin, and IgG subclasses quantified by ELISA; mean levels were 86.5% IgG1, 1.4% IgG2, 11.6% IgG3 and 0.4% IgG4. IgG1 and IgG3 polyclonal anti-D were further purified separately from some of the anti-D by removal of either IgG3 using magnetic beads coated with anti-IgG3, or of IgG1 using protein A. These preparations were compared with monoclonal anti-D (BRAD-3 and BRAD-5) for their ability to lyse red cells in antibody-dependent cell-mediated cytotoxicity (ADCC) assays.

RESULTS

Monocyte-mediated lysis of red cells coated with IgG3 anti-D was approximately twice that of cells coated with IgG1 anti-D at similar sensitization levels, and anti-D preparations containing 10% or more IgG3 gave similar lysis. By contrast, in the K cell ADCC, IgG1 anti-D was 2-4 times more haemolytic than IgG3 anti-D. Polyclonal IgG1 and IgG3 anti-D promoted about 20% more lysis than BRAD-5 (IgG1) and BRAD-3 (IgG3), respectively, in the K cell ADCC, although no difference was observed between polyclonal and monoclonal anti-D in the monocyte ADCC.

CONCLUSIONS

These experiments demonstrated a functional dichotomy between these two subclasses of anti-D; IgG3-coated red cells were lysed preferentially by monocytes mediated predominantly through Fc gamma R1 interactions, whereas haemolysis of IgG1-sensitized cells was mediated mainly by Fc gamma RIII on K cells.

Role of antibody dependent cell mediated cytotoxicity in ABO hemolytic disease of the newborn

Study includes fifty O blood group mothers delivering A or B group infants suffering from jaundice and a control group consisting of thirty one O group mothers of non-jaundiced infants. Lytic ability of maternal IgG anti-A/anti-B was determined by 51Cr ADCC assay in which cord blood monocytes were used as effector cells. In control series mean% specific lysis (SL) was 18 +/- 3.1 for IgG anti-A and 17.9 +/- 3.1 for IgG anti-B. In jaundiced series IgG anti-A was more lytic than IgG anti-B. However, the increase in ADCC lysis was statistically insignificant. Even though > 1:32 titre was more often associated with > 35% SL, in general the immune A/B antibody titre showed poor correlation with ADCC lysis. Majority of the severe ABO-HDN cases had > 35% ADCC lysis.

Antibody-dependent cell-mediated cytotoxicity (ADCC) in Parkinson's disease

The possible role of a non-specific cell-mediated immune reaction in the pathogenesis of Parkinson's disease (PD) is discussed. It was found that the killer cell activity of PD patients below 60 years of age was significantly lower than in the older age groups or in the age-matched control group. On the other hand, it was also found that the killer cell activity of PD patients with severe symptoms (Hoehn-Yahr's IV, V stage) was significantly higher than that of the milder cases. These results support the hypothesis that an ADCC reaction--mediated by the killer cells--may play a role in the pathogenesis of PD.

Haemolysis mediated by anti-D monoclonal antibodies in direct and cold target competition ADCC assays

Thirteen IgG anti-D human monoclonal antibodies (mAbs) were compared for their ability to mediate lysis of D-positive erythrocytes by PBMC in direct and cold target competition antibody-dependent cell-mediated cytotoxicity (ADCC) assays. In the latter assay, lysis of fluid-phase anti-D-sensitised O Rh D-positive papainised erythrocytes (E-IgG) was inhibited by A (or B) Rh D-negative papainised erythrocytes sensitised by fluid-phase anti-A (or anti-B) mAbs. The competitive and lytic activities of the anti-D mAbs were characterised by the equilibrium dilution (ED) values, which were the reciprocal of the dilution of anti-A (or anti-B) at which lysis of target E-IgG and competitor E-IgG were identical. There was a poor correlation between the number of erythrocyte-bound anti-D molecules and either the sensitivity of E-IgG anti-D to haemolysis in the direct ADCC assay, or to the ED values of the mAbs obtained in the cold target competition ADCC. The discriminatory power of the cold target competition ADCC was better than than of the direct ADCC to detect differences in the lytic potential of the anti-D mAbs.

Comparison of lysis of bromelain and papain treated red cells in ADCC assays

Red cells were pretreated with the proteolytic enzymes bromelain or papain prior to use in antibody-dependent cell-mediated cytotoxicity (ADCC) assays with lymphocytes or peripheral blood mononuclear cells (PBMC) as effector cells. At low concentrations of anti-D or anti-A, lysis of papain-treated cells by lymphocytes was greater than that of bromelain-treated cells. Papain digestion resulted in both greater sensitivity to haemolysis by lymphocytes or PBMC and higher agglutination titres of anti-D-sensitised red cells than bromelain. With anti-A, however, although papain also promoted greater haemolysis, it was slightly less effective at red cell agglutination than bromelain.

Antibody-dependent cell-mediated cytotoxicity to beta-lactoglobulin-coated cells with sera from children with intolerance of cow's milk protein

The capacity of serum antibodies against beta-lactoglobulin to mediate antibody-dependent cell-mediated cytotoxicity (ADCC) was analysed in sera from children with cow's milk protein intolerance (CMPI). The children with CMPI were divided into three groups according to clinical features: delayed-onset CMPI with gastrointestinal symptoms (n = 8); immediate-onset CMPI with gastrointestinal and skin symptoms (n = 8); and immediate-onset CMPI with skin symptoms only (n = 8). The CMPI groups were compared with children with untreated (n = 9) or treated (n = 8) coeliac disease and a control group (n = 22). Sera from the children were examined for cytotoxic effects using lymphocytes from healthy adults as effector cells and radiolabelled beta-lactoglobulin-coated erythrocytes from the same donor as target cells. In addition, IgG and IgA serum antibodies against beta-lactoglobulin were determined with ELISA. Sera from children with CMPI and gastrointestinal symptomatology showed a significantly increased capacity to induce ADCC reactivity as compared with controls. This increased capacity was seen in sera from those with immediate as well as delayed onset of the gastrointestinal symptoms. In contrast, sera from children who had an immediate-onset CMPI with only skin symptoms mediated no such increase in ADCC reactivity. Moreover, children with coeliac disease with a few exceptions, demonstrated low ADCC reactivity, despite the fact that they had high levels of antibodies against beta-lactoglobulin. ADCC may be an immunopathogenic mechanism in certain cases of CMPI with gastrointestinal symptoms.

The role of antibody density in the immune lysis of sensitised erythrocytes. A mathematical appreciation

The influence of sensitizing antibody density on target cell selection by effector monocytes was examined by modifying the sensitization of red cells either by dilution of the antiserum, variation of the number of erythrocytes or both in a cold target competition assay of antibody-dependent cellular cytotoxicity (ADCC). Human A1 and B erythrocyte target and competitor cells were employed in the presence of hyperimmune anti-A and anti-B sera at concentrations above that necessary for saturation of red cells with respect to lytic susceptibility. When the number of red cells was kept constant and the dilution of antisera was varied a linear relationship between the competitive capacity of erythrocytes and the concentration of sensitizing antiserum was observed. When the number of target (competitor) cells and the concentration of antisera were varied simultaneously it was apparent that the competitive capacity was dependent upon the relative densities of the sensitizing antibodies. When competition was tested in the presence of suboptimal concentrations of complement, rather than effector cells it was observed that, in common with ADCC, the effectiveness of cold competition was dependent upon the concentration of sensitizing antibody.

Immunological and molecular biological identification of a true case of T-hairy cell leukaemia

A hairy cell leukaemia (HCL) patient is presented in whom the peripheral blood mononuclear cells (PBMCs) carried suppressor T-cell markers (CD3+, CD2+, CD8+/CD4-, CD38+). Analysis of genomic DNA of PBMNC showed the presence of a monoclonal population of T cells, the T-cell receptor (TCR) beta-chain gene being rearranged on both alleles (DR/DR), while the immunoglobulin (Ig) heavy chain-genes were in germline configuration. The neoplastic cells were found to react with the monoclonal antibody RAB-1 - originally described as belonging to the B lineage-restricted monoclonal antibodies - and to carry RAB-1/CD-8 in a double marker assay. Natural killer activity of PBMNCs against K562 target cells was severely reduced, while the cells were found to exert strong antibody-dependent cellular cytotoxicity.

Human monoclonal anti-D antibodies. II. The relationship between IgG subclass, Gm allotype and Fc mediated function

Eight monoclonal antibodies (mabs) to the Rh antigen D produced by Epstein-Barr virus transformed B-lymphoblastoid cell lines from two individuals have been compared for their behaviour in in vitro cell-mediated assays. Three IgG1 Glm(1,17) and two IgG3 G3m(21) mabs from one donor and three IgG1 Glm(3) mabs from another were used. IgG3 anti-D mabs induced greater adherence and phagocytosis of sensitized red cells by U937 monocytes than IgG1 anti-D mabs or the polyclonal anti-D. Minimum sensitization levels for rosetting and phagocytosis by U937 monocytes were 2,000 molecules IgG/cell for IgG3 and 5,000 molecules/cell for IgG1 mabs; maximum rosetting mediated by both IgG1 and IgG3 mabs was obtained at 15,000-20,000 molecules/cell. The IgG3 anti-D mabs were comparable to polyclonal anti-D in mediating binding of sensitized red cells to gamma-interferon stimulated monocyte-derived cultured macrophages and were markedly more effective than the IgG1 anti-D mabs. However, in lymphocyte ADCC assays, only anti-D mabs which were IgG1 Glm(3) were effective in mediating high levels of lysis of sensitized red cells, unlike the IgG1 Glm (1,17) or IgG3 G3m(21) mabs. Minimum sensitization levels required for this lymphocyte-mediated red cell lysis were found to be approximately 5,000 molecules/cell with one IgG1 Glm(3) mab; maximum lysis with this mab was obtained at 10,000 molecules/cell. Polyclonal anti-D containing both IgG1 and IgG3 was effective in all three assays. These observations suggest that different isotypes and allotypes of anti-D antibodies mediate red cell removed or destruction by monocyte or lymphocyte effector cell through functionally dissimilar Fc receptor interactions.

Hairy cell leukaemia: observations on natural killer activity in different clinical stages of the disease

Follow-up studies of natural killer (NK) cells, NK activity and antibody dependent cellular cytotoxicity (ADCC) in the course of hairy cell leukaemia (HCL) were carried out in a series of patients affected by the disease. NK activity against K562 targets was found to be high in all the patients with non-symptomatic stable disease. On the other hand, absent or extremely low NK activity was found only in patients with symptomatic progressive disease. NK activity determined in the transitional stages showed values between these two extremes. Antibody dependent cellular cytotoxicity (ADCC) was less closely correlated with the clinical stage than NK activity. Our findings suggest that investigation of in vitro NK cell cytotoxicity might serve as a useful adjunct in determining clinical stage in HCL.

Fetal blood sampling in Rh hemolytic disease

Fetal blood sampling under ultrasound guidance has added a new dimension to the management of Rh hemolytic disease. Combined with the established parameters of history, antibody measurement and amniotic fluid delta OD450 readings, direct testing of the blood of the fetus completes the picture. As well as giving information that may be applied to decisions regarding management, an opportunity is provided to observe the mechanism of anti-D IgG-induced red cell destruction in vivo.

Heterogeneity of IgG1 monoclonal anti-Rh(D): an investigation using ADCC and macrophage binding assays

Three monoclonal IgG1 anti-Rh(D), UCH D4, ARC 7D5 and UKTS FC3, produced by Epstein-Barr virus transformed cells from Rh(D)-sensitized individuals, were compared with polyclonal single donor anti-D sera and therapeutic immunoglobulin preparations in antibody dependent cellular cytotoxicity (ADCC) and macrophage binding tests. When assayed at equal anti-D concentrations monoclonal antibodies varied considerably in their ADCC and macrophage binding activities: only UKTS FC3 showed significant activity in both assays, but these were substantially lower than those of the polyclonal anti-D sera and immunoglobulins. When examined in different combinations the monoclonal antibodies showed little synergism in mediating red cell destruction by the effector cells. Factors which might contribute to the diverse ADCC and macrophage binding activities of the monoclonal anti-Ds of the same IgG subclass are discussed.

Further investigation of nonspecific biological substance in anti-Rh(D) preparations

Fc receptor-blocking activity, based on the EA rosetting inhibition of anti-Rh(D) gamma-globulin preparations, was determined during biological analyses. After sample purification by means of precipitation with a low concentration of ammonium sulphate, fractions were obtained containing anti-D activity and Fc receptor-blocking activity separately. Fc receptor-blocking antibodies inhibited both the formation of EA rosettes and the antibody-dependent cellular cytotoxicity activity. It is suggested that Fc receptor-blocking antibodies obtained during hyperimmunization probably result in the immunosuppressive effect of Rh immune globulin (via the blocking of Fc receptors of activated lymphocytes) that decreases in turn the progress of Rh immunization.

Fc receptors for IgG1 and IgG3 on human mononuclear cells--an evaluation with known levels of erythrocyte-bound IgG

The Fc receptors on mononuclear cells were investigated by a rosette technique in which human erythrocytes were sensitized with a known number of molecules of anti-Rh antibodies (IgG1 or IgG3). The number of IgG molecules was quantitated by a radiometric antiglobulin test. The present quantitative evaluation reveals that (1) there is a logarithmic relationship between the proportion of rosettes and the amount of erythrocyte-bound immunoglobulin for both types of mononuclear cells, and for both subclasses; (2) similar percentage of rosettes can be obtained with fewer IgG3 than IgG1 molecules (about 1:4); (3) for a given number of erythrocyte-bound immunoglobulins a higher percentage of rosettes is observed with monocytes than with lymphocytes (ratios of about 3:1 for IgG1 and 5:1 for IgG3); (4) the minimum number of IgG3 molecules for adherence is 180-460 for monocytes, 520-1,300 for lymphocytes, whilst for IgG1 the numbers are 1,180-4,300 for monocytes and 3,400-14,200 for lymphocytes; (5) the minimum levels of sensitization by alloantibodies for adherence should be detectable by the antiglobulin test.

ADCC lysis of human erythrocytes sensitized with rhesus alloantibodies. IV. Characterization of anti-D sera which are inactive in ADCC

Certain anti-D sera, selected on the basis of their agglutination characteristics in vitro, fail to induce lysis of Rh(D) positive red cells by lymphocyte mediated antibody dependent cell mediated cytotoxicity (ADCC). Further investigation revealed that the non-lytic anti-D blocked in an antigen specific manner the effect of other anti-D sera which were normally lytic in ADCC. Absorption selection studies and fractionation of a non-lytic anti-D serum showed that the blocking effect was associated with IgG anti-D. Antigen binding and lymphocyte Fc-receptor binding studies indicated that the non-lytic anti-D was bound to Rh(D) positive red cells and enabled them to be bound by lymphocytes, but failed to mediate ADCC.

Autoimmune hemolysis: a critical review

Autoimmune hemolysis is defined as a shortening of erythrocyte lifespan due to antibodies directed against the individuals own red cells. This autoantibody production (by B lymphocytes) is thought to result from deficient activity of suppressor T lymphocytes. The rate of erythrocyte destruction depends on the properties of the autoantibodies and on the activities of the complement and mononuclear phagocyte systems: anemia results when destruction outweighs marrow production. Autoimmune hemolysis, which may be primary or secondary, is classified into "warm," "cold," and "mixed" types. The hemolysis associated with pregnancy. Donath-Landsteiner antibodies, of mixed type, and in children, is treated in detail. Current treatment is with immunosuppressive drugs, surgery, and plasma exchange, though immunomanipulation may become important in the future; blood transfusion may be a life-saving adjunct to other therapy.

Antibody dependent cell-mediated cytotoxicity in different forms of rheumatoid arthritis patients

The activity of peripheral blood lymphocytes from 61 patients with rheumatoid arthritis (RA) was examined in the antibody dependent cell-mediated cytotoxicity (ADCC) test in the allogenous system. The control group consisted of 86 healthy donors. Also, the effect of sera from RA patients upon the normal lymphocytes in ADCC was studied and the EA rosette test was performed. A significant decrease in the cytotoxic activity of peripheral blood lymphocytes was found in RA patients, this being dependent on the form of RA rather than laboratory evidence of the inflammatory process. Particularly poor cytotoxic activity was revealed in rheumatoid subjects with the coexisting laboratory evidence of systemic lupus erythematosus (SLE) and amyloidosis. It seems that factors inhibiting lymphocyte cytotoxicity in the ADCC test are of a complex nature.

K cell mediated haemolysis: influence of large numbers of unsensitized cells on the antibody-dependent lysis of anti-D-sensitized erythrocytes by human lymphocytes

The inhibition of K cell mediated haemolysis of anti-D-sensitized human red blood cells by unsensitized erythrocytes has been demonstrated. Inhibition of lysis was non-competitive in nature and influenced by the size and number of unsensitized cells. However, even in the presence of high inhibitor: target cell ratios (50:1) haemolysis, although reduced, was still effected suggesting that K cells are highly motile and capable of recognizing and destroying minority populations of antibody-sensitized erythrocytes. These data are compatible with a role for cytotoxic lymphocytes in the intravascular lysis of autoantibody or alloantibody-sensitized red cells.

Measurement of K cell activity: use of human OR1R1 red cells and anti-D to study the role of different leucocytes as effector cells

A method for quantitative assay of K cell activity (KCA) with an allogenic combination of human OR1R1 red cells and anti-D (IgG, incomplete antibody) as target cells is described. Lymphocytes alone have been shown to cause lysis of these target cells. Fc receptor-bearing lymphocytes appear to be the chief mediators of KCA. This sub-population is a heterogeneous mixture of sub-sets of other sub-populations defined on the basis of different surface markers and likely to show variable expression of Fc receptors by the EA gamma rosette method. Monocytes and neutrophils (and possibly eosinophils), most of which bear Fc receptors, are ineffective as effector cells. Monocytes may in some instances have an inhibitory effect on the expression of KCA of lymphocytes. The method described has the advantage of simplicity (easy availability of OR1R1 cells and anti-D) and a high degree of sensitivity (marked lysis at low L/T ratio) and appears suitable for routine use in clinical practice.

Simultaneous detection of two mechanisms of immune destruction of penicillin-treated human red blood cells

Two separate processes of putative red-cell destruction in penicillin-induced immune hemolysis were measured simultaneously by a rapid (3 hour) assay utilizing 51Cr-labelled red blood cells (RBC). Antibody-dependent, cell-mediated cytotoxicity (ADCC) was estimated by release of 51Cr; and antibody-dependent phagocytosis (ADPh) by quantitation of 51Cr uptake into mononuclear phagocytes as well as by counts of engulfed RBC. Attacking cells were obtained by Ficoll-Hypaque separation of peripheral blood from normal donors. Phagocytosis as well as lysis were proportional to anti-penicillin antiserum concentration, to incubation time, and to the concentration of the attacking cells. Enrichment of mononuclear phagocytes in the attacking cell population by albumin gradient separation led to an increase in phagocytosis as well as in cytotoxicity. Depletion of mononuclear phagocytes resulted in a decline in both processes. Dilution of antiserum abolished ADCC but affected ADPh only slightly. Iodoacetate as well as colchicine inhibited both activities. These results indicate that both processes may be operative in the immune destruction of RBC in vivo.

Antibody-dependent cell-mediated cytotoxicity against Escherichia coli O antigens

Antibodies against Escherichia coli O antigen from rabbits immunized with formalin-killed bacteria were tested for cytotoxic capacity in an antibody-dependent cell-mediated cytotoxicity (ADCC) assay with human lymphocytes as effector cells and autologous papainized erythrocytes coated with O antigen as target cells. The cytotoxic titres were compared with the titres obtained with three methods of antibody quantitation. It was found that ADCC recorded antibodies with similar sensitivity as the enzyme-linked immunosorbent assay (ELISA) for IgG, but was much more sensitive than the ammonium sulphate precipitation (ASP) and indirect haemagglutination (IHA) using beta-mercaptoethanol reduced sera. The ADCC titres were found to correlate very well with the titres obtained with ASP, ELISA and IHA for IgG but not for IgM, which is in accordance with a previous notion that ADCC is primarily mediated via IgG antibodies. ADCC should be considered as a possible immunopathologic mechanism in renal parenchymal damage in connection with urinary tract infections.

Direct ADCC lysis of O,Rh-positive (R1R2) erythrocytes by lymphocytes of individuals sensitized against antigen D

Non-T-cells from individuals sensitized against antigen D were found to lyze O,Rh-positive erythrocytes. The lytic effect was abolished by incubation of the effector cells at 37 degrees C for 30 min, and was reconstituted by addition of anti-D antibodies. These results suggested that sensitized donors have lymphocytes armed with specific antibodies in vivo.

Antibody-dependent cell-mediated cytotoxicity (ADCC) of penicillin-treated human red blood cells

Penicillin-treated human red blood cells (RBC) were lysed by the cooperation of autologous nonsensitized peripheral blood mononuclear cells and human anti-penicillin serum. Using a rapid (3 h) assay of antibody-dependent cell-mediated cytotoxicity (ADCC), lysis was proportional to serum (anti-penicillin antibody) concentration, to incubation time and to the concentration of attacking cells, which were obtained from normal human peripheral blood by Ficoll-Hypaque separation. Incubation of these lymphoid effector cells on a nylon column prior to the tests depleted the number of phagocytic (latex positive) cells in the effluent; there was a concomitant drop in cytotoxic activity. Enrichment of mononuclear phagocytes in the attacking cell population by albumin gradient separation led to an increase in cytotoxicity. Granulocytes separated by Ficoll-Hypaque were not active in this system. Using specific antisera the antibody was found to be of the IgG1 sub-class. Anti-penicillin antibody activated the complement system in vitro, but failed to induce lysis of penicillin-treated RBC in the presence of complement without attacking cells. These results suggest that ADCC may participate in the destruction of RBC in penicillin-induced haemolysis in vivo.

ADCC (K-cell) lysis of human erythrocytes sensitized with rhesus alloantibodies. III. Comparison of IgG anti-D agglutinating and lytic (ADCC) activity and the role of IgG subclasses

Conventional manual (enzyme and antiglobulin titres) and AutoAnalyser quantitation of anti-D sera were compared with the ability of the same sera to mediate lysis of Rh(D) positive red cells in an ADCC assay. AutoAnalyser (AA) quantitation correlated significantly with manual titration methods, although there were wide discrepancies between individual sera. The ADCC activity of the anti-D sera did not correlate with any of the conventional assays (AA, enzyme, antiglobulin). There were significant differences between anti-D sera obtained from females immunized during pregnancy and male volunteers immunized by deliberate injection. The female sera contained significantly less anti-D when assessed by AA, yet were significantly more active in ADCC activity at equivalent concentrations. These functional differences in anti-D activity could not be attributed to the absence of IgG subclasses (IgG1 and IgG3) known to induce ADCC. However, there was a relationship between ADCC and IgG1/IgG3 titres in that high ADCC activity was seen where the IgG3 titre was higher than the IgG1 titre. In the male anti-D sera IgG1 titres were greater than or equal to IgG3 titres and ADCC activity was very low.

Antibody-dependent, cell-mediated cytotoxicity against human red blood cells: correlation of effector cell type with enzymatic alteration of the target cell surface

Target cell factors, which contribute to the determination of the effector cell type in an antibody-dependent, cell-mediated cytotoxicity system were studied. Human red blood cells (RBC) were treated with papain and investigated by transmission and scanning electron microscopy (TEM and SEM). Both untreated (native) and treated 0 Rh+ RBC were labeled with 51Cr, sensitized with anti-D immunoglobulin and incubated with unfractionated autologous peripheral blood mononuclear cells. With native RBC, immune lysis was proportional to the number of phagocytes: enrichment of effectors in phagocytes increased lysis, while depletion of phagocytes from effectors decreased lysis. Following papain treatment of target RBC, lysis by unfractionated mononuclear effectors was markedly augmented; since this effect was not diminished by decrease of phagocytes to less than 2%, the augmented lysis was not due to the number of phagocytic effectors. TEM and SEM of enzyme-treated RBC showed spherocytosis with varying degrees of crenation and blurring and irregularities of the cellular membranes. The results suggest that papain-induced alterations in the target RBC rendered them susceptible to lysis by interaction between anti-D antibody and peripheral blood lymphocytes.

Quantitative evaluation of antibody-dependent lymphocyte-mediated lysis of human red cells

The ability of lymphocytes to lyse human red cells coated with anti-D antibody was assessed by measuring 51 Cr release from labeled red cells incubated with peripheral blood leukocyte suspensions from 12 normal donors. Mixed mononuclear cell suspensions (containing monocytes and lymphocytes) from all donors produced lysis of sensitized red cells. Treatment with carbonyl iron reduced monocyte concentration to less than 1.2% in all donors, as measured by morphologic criteria, esterase staining and ingestion of latex particles. Lysis of red cells following monocyte depletion was markedly reduced in 8 of the 12 donors. Despite depletion of monocytes, unchanged or increased lysis was noticed with the leukocytes of the remaining 4 donors. This lysis was due to lymphocytes, not to residual monocytes. If target red cells were treated with papain or trypsin prior to sensitization, marked lysis occurred with lymphocytes of all donors, including those which did not lyse unmodified red cells. Direct cytolysis of sensitized red cells during contact with small lymphocytes was recorded using microcinematography, which confirmed the role of lymphocytes in mediating lysis. Lymphocyte-mediated lysis of red cells increased with mounting levels of antibody sensitization regardless to prior treatment with papain. Papain increased antibody coating per red cell, yet lysis per molecule of antibody bound was also increased. Lysis was inhibited by IgG1 and IgG3 in the fluid phase but not by IgG2 or IgG4. At an equivalent level of antibody sensitization lysis was augmented by concurrent coating of the red cells with C3b, C3d and/or C4b, though these components could not produce lysis in the absence of antibody coating.

ADCC (K-cell)lysis of human erythrocytes sensitized with rhesus alloantibodies. I. Investigation of in vitro culture variables

An ADCC system has been developed using anti-D and papainized group O rhesus (D) positive red cells as the targets. Monocyte depleted mononuclear cell suspensions were effective in lysing appropriately sensitized red cells and papainization considerably enhanced the degree of specific lysis. Variation in culture volume and incubation in tubes or microplates were not critical to the degree of specific lysis obtained provided that the number of effector cells and target cells per culture was constant and the anti-D not diluted below the optimal concentration. Cytolytic activity was seen down to levels of 3 ng anti-D per culture. Specificity for lysis resided with the anti-D and not the effector cells. Several sources of anti-D were effective in inducing lysis of D positive red cells although individual variation was noted. Anti-c and anti-E were also shown to be effective in inducing specific lysis of red cells with the appropriate antigens.

ADCC (K-cell) lysis of human erythrocytes sensitized with rhesus alloantibodies. II. Investigation into the mechanism of lysis

The mechanism of lysis of anti-D coated human erythrocytes by human mononuclear K-cells was investigated. Red cell lysis was measurable after 30 min incubation and reached a maximum by 18--20 h. Cell-to-cell contact was necessary for lysis, phagocytosis was not a prerequisite, and intact microfilament function was required. The divalent cations Ca2+ and Mg2+ were both required for lysis to occur. Studies with metabolic inhibitors indicate that some RNA and protein synthesis is required for maximum expression of ADCC and intact microtubule function is essential. In the present system lysis was mediated by IgG1 anti-D antibodies and was significantly inhibited by IgG1 and IgG3 subclasses with some inhibition by IgG2 but not by IgG4, IgA or IgM. This suggests that the K-cell receptor is specific for IgG but that there is major cross-reactivity between IgG1 and IgG3. The inhibiting effect of hydrocortisone suggests that ADCC inhibition may be one mode of action of corticosteroids in ameliorating autoimmune haemolytic anaemia.

Characteristics of different rhesus alloantibodies in lymphocyte dependent (K cell) cytotoxicity to human erythrocytes

The property of rhesus alloantibodies to elicit antibody-dependent, cell-mediated cytotoxicity (ADCC) against target erythrocytes carrying various Rh genotypes was studied. The killer activity of normal peripheral lymphocytes on human erythrocyte target cells carrying the appropriate antigens elicited by alloantisera was measured by 51Cr release at 18 h. There was no correlation between ADCC and antibodies directed to the antigens present on the surface of different genotypes of Rh-positive red blood cells. The agglutinin titre of different Rh antibodies showed no correlation with the level of ADCC although the degree of cellular cytotoxicity was different with different anti-D sera. Anti-C + D+ E antibody caused higher ADCC than anti-C + D and the lowest cytotoxicity was observed with anti-D and anti-D+ E. This raised the possibility that ADCC was elicited by antibodies directed to other specificities. K cell lysis of human red cells by human peripheral blood lymphocytes in vitro suggests that a similar mechanism may operate in vitro in the destruction of erythrocytes coated by allo or autoantibodies.

Destruction of sensitized erythrocytes by human monocytes in vitro: effects of cytochalasin B, hydrocortisone and colchicine

The purpose of this study was to characterize the destruction of sensitized erythrocytes by human blood monocytes in vitro. The incubation in vitro of human monocytes with 51Cr-labelled human erythrocytes sensitized with IgG rhesus alloantibodies anti-D (EAIgG anti-D) resulted in release of 51Cr from the erythrocytes (lysis) as well as uptake of 51Cr-labelled erythrocytes by the monocytes (phagocytosis). The lysis of EAIgG anti-D by monocytes was not dependent on phagocytosis, because cytochalasin B, which inhibited phagocytosis of EAIgG, enhanced lysis. In contrast, hydrocortisone and colchicine inhibited lysis, but had no effect on phagocytosis. These agents did not affect binding of EAIgG anti-D to monocytes. The effect of these agents on lysis corresponded to their effect on release of lysosomal enzymes by monocytes. The release of lysosomal enzymes, when induced by EAIgG anti-D, was, likewise, enhanced by cytochalasin B and inhibited by hydrocortisone and colchicine. A significant correlation was found between lysosomal enzyme release and lysis. Together, these results strongly suggest that lysosomal enzymes, released by the monocytes when incubated with anti-D-sensitized erythrocytes, are responsible for the cytotoxic activity of these cells towards sensitized erythrocytes. The action of these enzymes only occurs over a short range, probably at the site of attachment of the erythrocyte, because only erythrocytes that were bound to the monocytes were lysed. The finding of other investigators that removal of monocytes from suspensions of human mononuclear leucocytes results in a strong reduction in the cytotoxic activity of these leucocytes towards sensitized erythrocytes in vitro. was confirmed.

Lymphocyte-mediated antibody-dependent cytolysis: role in immune hemolysis

Peripheral blood lymphocytes obtained from normal volunteers were capable of lysing Rh(D)-positive human erythrocytes in the presence of IgG anti-Rh(D) antibodies. The percent cytotoxicity produced by peripheral blood lymphocytes was approximately equivalent to that produced by unfractionated peripheral blood mononuclear cells. Neither peripheral blood mononuclear cells nor peripheral blood lymphocytes lysed Rh(D)-negative human erythrocytes in the presence of IgG anti-Rh(D) antibody.