Heteroantibody-mediated cytotoxicity: antibody to the high affinity Fc receptor for IgG mediates cytotoxicity by human monocytes that is enhanced by interferon-gamma and is not blocked by human IgG

An IgG1 monoclonal antibody, 32.2, raised against the 72,000 dalton monocyte high affinity Fc receptor, was used to examine the role of this receptor in ADCC. This antibody did not inhibit the binding of human IgG1 to monocytes or to the U937 cell line, nor did it block or stimulate their killing of IgG-coated chicken erythrocytes (CE). Whole 32.2 or its Fab fragments were cross-linked to Fab fragments of rabbit anti-CE by using the agent SPDP. The resulting heteroantibodies (32.2 X Fab anti-CE) mediated monocyte and U937 cytotoxicity against CE, whereas an anti-HLA X anti-CE reagent did not. Both FcR expression and heteroantibody-mediated cytotoxicity were increased by culturing monocytes or U937 with IFN-gamma. Although IgG-mediated ADCC was significantly inhibited by 40 micrograms/ml human IgG1, cytotoxicity mediated by 32.2 X Fab anti-CE was not blocked by 2 mg/ml human IgG1, suggesting that such cytotoxicity might not be blocked by IgG in vivo. These data indicate the potential of 32.2 heteroantibodies in analysis of FcR function and in therapy.

Glucocorticoid enhances gamma interferon effects on human monocyte antigen expression and ADCC

The expression of HLA-DR antigen by highly enriched human monocytes cultured in serum free medium was found to be markedly elevated by human recombinant gamma interferon (IFN-gamma). This effect was maximal after 48 h in culture with 300 mu/ml IFN-gamma. Class I MHC antigen also increased with IFN-gamma treatment. By contrast, binding of a myeloid-specific monoclonal antibody, AML-2-23, was dramatically decreased by IFN-gamma. The augmentation of MHC antigens was not ablated by an immunosuppressive concentration (2 X 10(-7) M) of the glucocorticoid dexamethasone (DEX). In fact, both the enhancement of Class I and Class II MHC antigen expression and the suppression of AML-2-23 antigen by IFN-gamma were often more profound in the presence of DEX. IFN-gamma treatment also resulted in elevated monocyte effector function, as measured by antibody dependent cellular cytotoxicity (ADCC). This functional activation was not inhibited by DEX. On the contrary, DEX slightly augmented IFN-gamma effects on ADCC. This contrasts with other reports that glucocorticoids inhibit monocyte responsiveness to lymphokines, and suggests that the interplay between lymphokines and the glucocorticoid hormones may be more complex than previously thought.

IgA-mediated effector function of HL-60 cells following treatment with calcitriol

When cells of the HL-60 promyelocytic leukemia line are cultured with 1,25-dihydroxyvitamin D3 (calcitriol) they acquire a more highly differentiated, myelomonocytic phenotype. It was observed that the ability to ingest IgA-coated erythrocytes and to bind soluble dimeric IgA accompanied this maturation. Phagocytosis of IgA-coated erythrocytes was greater than 50% inhibited by 0.8 mg/ml free IgA, and not by IgG or IgM. Similarly, binding of dimeric IgA was not blocked by a 100-fold excess of IgG, IgM or IgE. Both IgA-mediated phagocytosis and IgA binding became apparent after two days of culture with calcitriol and increased with time in culture. The induction of functional IgA receptors was evident with 10(-11) M calcitriol and maximal levels of IgA binding and of numbers of cells capable of IgA mediated phagocytosis were induced by 10(-8)-10(-9) M calcitriol. 25-Hydroxyvitamin D3, which binds 100-1000-fold less avidly to the cytoplasmic D3 receptor than calcitriol, did not induce functional IgA receptors unless concns of 10(-7) M were used. Other compounds which induce differentiation of HL-60 cells, including retinoic acid and DMSO, produced similar results to calcitriol, whereas cells treated with gamma interferon expressed lower levels of IgA binding and did not ingest IgA-coated targets, suggesting that a critical density of IgA receptors must be reached to enable phagocytosis and/or that other cell activational events are required for IgA receptors to mediate killing. This model may provide useful insight into the function and regulation of IgA receptors on cells of the myeloid series.

Nuclear magnetic resonance studies of carbohydrate metabolism and substrate cycling in Fasciola hepatica

We have been interested in clarifying unique features of glycolytic metabolism in parasitic trematodes and in developing improved methods for monitoring the effects of pharmacologic agents that may alter functions of the pathway. In the present study metabolism of [1-13C]glucose by the common liver fluke, Fasciola hepatica, was studied both directly with 13C NMR and indirectly by observation of 13C-induced multiplet splitting of the 1H NMR resonances from the glycolytic end-products propionate and acetate. The extent of 13C enrichment of the end-products demonstrated that exogenous glucose was the predominant source of glycolytic substrate under the incubation conditions used. Specific enrichments of propionate and acetate in 13C were similar and enrichments at the acetate C-1 carboxyl and C-2 methyl were identical, demonstrating that acetate is generated preferentially from pyruvate formed by the malic enzyme reaction. End-product synthesized in substrate-free medium following incorporation of a small fraction of [1-13C]glucose into endogenous glycogen demonstrates that glucose equivalents from the most recently synthesized polymeric chains, which have a specific activity in 13C equal to that of the exogenous glucose, are preferentially used for glycogenolysis. Stimulation of flukes with 0.1 mM serotonin results in a reduction of the propionate/acetate 13C enrichment ratio consistent with functional "compartmentation" of glycogen pools having different structures and/or specific enrichment in 13C. Glucose equivalents were incorporated into glycogen in intact flukes with label at both the C-1 and C-6 positions during perfusion with [1-13C]glucose as a consequence of "substrate cycling" at the phosphofructokinase/fructosebisphosphatase enzyme couple. The observed glycogen C-6/C-1 labeling ratio of 0.42 and the net glycolytic flux of 11 mumol/g wet weight/hr imply a total forward flux of about 29 mumol/g wet weight/hr through phosphofructokinase with a reverse flux of about 17 mumol/g wet weight/hr through fructosebisphosphatase. Net glycolytic flux is therefore a poor estimate of the true flux through phosphofructokinase in this preparation.

The expression of receptors for IgA on human monocytes and calcitriol-treated HL-60 cells

In this study, we investigated the expression of IgA Fc receptors (FcR alpha) by human myeloid cells. By using a sensitive cytofluorometric IgA binding assay, we found that approximately 85% of peripheral blood monocytes bound IgA in an isotype-specific fashion. The HL-60 human promyelocytic leukemia cell line failed to express FcR alpha; however, treatment of HL-60 cells with the differentiating agent calcitriol induced the expression of FcR alpha on greater than 90% of these cells. Monocytes and calcitriol-treated HL-60 cells were capable of ingesting IgA-coated erythrocyte targets, suggesting that phagocytosis could be mediated through FcR alpha. The induced HL-60 cell system represents a useful model for further studies on FcR alpha expression and function.

The expression of receptors for IgA on human monocytes and calcitriol-treated HL-60 cells

In this study, we investigated the expression of IgA Fc receptors (FcR alpha) by human myeloid cells. By using a sensitive cytofluorometric IgA binding assay, we found that approximately 85% of peripheral blood monocytes bound IgA in an isotype-specific fashion. The HL-60 human promyelocytic leukemia cell line failed to express FcR alpha; however, treatment of HL-60 cells with the differentiating agent calcitriol induced the expression of FcR alpha on greater than 90% of these cells. Monocytes and calcitriol-treated HL-60 cells were capable of ingesting IgA-coated erythrocyte targets, suggesting that phagocytosis could be mediated through FcR alpha. The induced HL-60 cell system represents a useful model for further studies on FcR alpha expression and function.

1,25-Dihydroxyvitamin D3 induces a myelomonocytic phenotype with enhanced effector cell function in the HL-60 promyelocytic leukemia cell line

Human promyelocytic leukemia (HL-60) cells were induced by 1,25-dihydroxyvitamin D3 (calcitriol) to differentiate and examined using a panel of monoclonal antibodies (MoAbs) and functional assays. Although morphologically and histochemically these cells appeared to be of the monocyte-macrophage phenotype, there was a decline in Fc receptors for IgGl and no induction of class II HLA antigens. There was, however, dramatic induction of the antigen detected by the myeloid-specific MoAb AML-2-23. These data suggest that the phenotypic changes induced by calcitriol in HL-60 cells are consistent with myelomonocytic differentiation in that the resultant cells possess characteristics of both monocytes (morphology, non-specific esterase staining, high levels of AML-2-23 reactivity) and granulocytes (PMN 29 binding, decreased Fc receptors for IgGl, absence of class II HLA antigens). Perhaps more important, the ability of calcitriol-treated cells to perform antibody-dependent cellular cytotoxicity and phagocytosis was markedly augmented. Lysis of antibody-coated erythrocytes by HL-60 cells increased from 5% in controls to 30-35% with calcitriol treatment for 4 days. This enhanced effector cell function was seen despite a decline in Fc receptors measured by cytofluorography. These data suggest that calcitriol may be involved in both differential and functional activation of myeloid cells.

Differentiation of a human monocytic cell line by 1,25-dihydroxyvitamin D3 (calcitriol): a morphologic, phenotypic, and functional analysis

Several recent studies have suggested a role for 1,25-dihydroxyvitamin D3 (calcitriol) in myeloid differentiation. We have examined the effects of calcitriol on the U937 monoblast cell line and found that calcitriol, at near physiologic concentrations, is a potent inhibitor of U937 growth. Moreover, calcitriol induces differentiation to a monocyte-macrophage phenotype marked by enhanced alpha-naphthyl esterase staining. Morphologic changes were attended by de novo induction of the myeloid specific antigen detected by the monoclonal antibody AML-2-23, as well as dramatic increases in Fc receptors for IgG. In addition, calcitriol induced U937 cells to perform phagocytosis and antibody-dependent cellular cytotoxicity. These results indicate the potential activity of calcitriol in myeloid differentiation and additionally suggest a role for calcitriol in monocyte-macrophage activation.

Immunological monitoring in patients with end-stage renal disease

Parameters of cell-mediated immune function were determined in 76 patients with end-stage renal disease. Lymphocyte subpopulations (OKT3, OKT4, OKT8, OKIa1, OKM1, OKT9, OKT10), natural killer (NK)-cell activity (percentage 51Cr release from K562 targets), and delayed cutaneous hypersensitivity were measured and correlated with other variables. The results indicate that (1) uremic patients have a significant diminution in the OKT4-lymphocyte subpopulation and OKT4/OKT8 (helper/suppressor) ratio compared to normal controls; (2 blood transfusions do not induce significant alterations in the helper/suppressor-cell ratio; (3) uremic patients have a significant increase in OKM1 cells compared to normal controls; (4) the majority of uremic patients in this series developed delayed cutaneous hypersensitivity responses to recall antigens and could be de novo sensitized to 2,4-dinitrochlorobenzene (DNCB); (5) skin-test reactivity could not be correlated with total circulating T cells or levels of any lymphocyte subpopulations; and (6) NK-cell activity in uremic patients is not significantly different from that in normal controls. These results highlight the varying levels and function of different lymphocyte subsets in patients with end-stage renal disease when they are treated with chronic maintenance hemodialysis.

Gamma interferon induces monocytoid differentiation in the HL-60 cell line

We investigated the ability of purified, recombinant DNA-derived interferons (IFN) to induce phenotypic changes in cells of the HL-60 promyelocytic leukemia cell line. Changes in cell surface markers detected by monoclonal antibodies as well as morphologic, histochemical, and functional changes were monitored. We found that gamma-IFN, but not alpha- or beta-IFN, induced the expression of antigens characteristic of monocytes and granulocytes (AML-2-23, 63D3, and 61D3), as well as changes in morphology consistent with monocytoid differentiation. These included induction of alpha-naphthyl acetate esterase, increased cell size, and a decrease in azurophilic granules. The gamma-IFN dose dependency and time course of the effect on antigen expression suggest that de novo protein synthesis was induced by gamma-IFN. The activity of gamma-IFN and of mixed-lymphocyte culture supernatant was blocked by a monoclonal antibody to gamma-IFN. Significant augmentation in the ability of the HL-60 cells to mediate antibody-dependent cellular cytotoxicity was induced by gamma-IFN. These findings suggest that gamma-IFN plays a role in the regulation of hematopoiesis.

Direct stimulation of ADCC by cloned gamma interferon is not ablated by glucocorticoids: studies using a human monocyte-like cell line (U-937)

We have used the macrophage-like cell line U-937 to demonstrate that recombinant gamma (immune) interferon (gamma-IFN) acts directly on the mononuclear phagocyte in the absence of other cell types to increase Fc receptor sites and antibody-dependent cellular cytotoxicity (ADCC). Incubation of U-937 for 18 hr with 2% gamma-IFN-rich supernatant, or with 10 U/ml of pure recombinant gamma-IFN, resulted in a seven-fold increase in Fc receptors as measured by the binding of radiolabeled IgG or fluoresceinated IgG and cytofluorography. Simultaneous measurement of ADCC for chick erythrocytes showed a seven-fold increase. This augmentation of Fc receptors and function was not ablated by an immunosuppressive cocn of the glucocorticoid dexamethasone. The potent effects of gamma-IFN both on surface receptors and effector functions of macrophages suggest that it is an important mediator in the efferent limb of immunity. Moreover, our findings that physiologic levels of glucocorticoids do not block activation of the mononuclear phagocyte support our view that glucocorticoids are immunosuppressive as a result of their action on gamma-IFN-producing cells. This would seem an important consideration in the development of potential strategies for obviating steroid-induced immunosuppression.

Cytofluorographic analysis of receptors for IgA on human polymorphonuclear cells and monocytes and the correlation of receptor expression with phagocytosis

Receptors for the Fc portion of IgA (RFc alpha) were identified on human monocytes and polymorphonuclear cells (PMNs) by cytofluorograph analysis using FITC-labeled IgA and by rosette formation with IgA-sensitized indicator cells. Larger percentages of PMNs obtained from the oral cavity expressed RFc alpha than did blood PMNs. These oral PMNs also expressed more RFc alpha per cell than blood PMNs. Moreover, the expression of these receptors on blood PMNs was enhanced by overnight incubation with IgA. In functional studies, RFc alpha appeared to cooperate with receptors for IgG in enhancing blood and oral PMN mediated phagocytosis of target cells coated with IgG and IgA. Furthermore, and in contrast with blood PMNs, oral PMNs were capable of phagocytosing target cells coated with IgA alone. Thus, receptors for IgA may be important to the ability of RFc alpha bearing effector cell populations to mediate protection at mucosal surfaces.

Contribution of fibrin stabilization to clot strength. Supplementation of factor XIII-deficient plasma with the purified zymogen

The contribution of fibrin stabilization to clot strength, measured as the static elastic modulus, was evaluated in human plasma by two independent procedures. In the first approach, amine inhibitors of fibrin stabilization were examined for their effects on the rigidity of normal plasma clots. It is a unique property of these inhibitors that they do not interfere with the reversible aggregation of fibrin molecules, i.e., do not delay clotting time, but selectively prevent only the formation of gamma-glutamyl-epsilon-lysine protein-to-protein linkages. Though the compounds tested were of different chemical structures and potencies, a fivefold reduction in clot strength was obtained in each instance. This value of 20% of normal seems to correspond to the rigidity of the Factor XIII-deficient plasma clot because, as demonstrated by the second approach, when a plasma specimen that genetically lacked the fibrin stabilizing factor was supplemented by the addition of measured amounts of the purified zymogen, a fivefold increase in clot strength could be achieved. The described procedure of evaluating Factor XIII in terms of correcting the elastic modulus of a deficient plasma clot is considered an important assay for the functional competence of purified preparations of the zymogen for the purpose of therapeutic application.

Monoclonal antibodies to novel myeloid antigens reveal human neutrophil heterogeneity

Three cytotoxic murine monoclonal antibodies that recognize myeloid-specific antigens have been produced by immunization with normal human neutrophils or myeloblasts from a patient with acute myelomonocytic leukemia. Two of these, PMN 6 and PMN 29, are specific for neutrophils; the third monoclonal antibody, AML-2-23, is reactive with the majority of normal monocytes as well as a subpopulation of mature neutrophils. Although neutrophils from all individuals tested expressed these antigens, cytofluorographic analysis revealed that the percentage of cells bearing the PMN 6 and AML-2-23 antigens varied among individuals. Significant additional heterogeneity in the density of each antigen among antigen-bearing cells was also observed. All three antibodies efficiently mediated complement-dependent cytotoxicity of acute myelocytic leukemia cells yet were unreactive with lymphocytic leukemia cells. Neutrophil cytotoxicity was mediated by PMN 6 and PMN 29 but not by AML-2-23. On the other hand, AML-2-23, but not PMN 6 or PMN 29, was cytotoxic for normal monocytes and macrophages. These monoclonal antibodies may be of value in the study of normal neutrophil function and differentiation and may have clinical utility in diagnosis and therapy of myeloid leukemia.

Studies on autoantibodies to poly (adenosine diphosphate-ribose) in SLE and other autoimmune diseases

Sera from 41 patients with systemic lupus erythematosus (SLE), 87 controls with various diseases, and 30 normal subjects were examined for poly (adenosine diphosphate-ribose) and ds DNA binding. Elevated levels of poly (ADP-ribose) binding were found in 73% of the SLE patients compared with 58% who had raised ds DNA binding. In a further study of 160 sera from 27 patients with SLE, levels of antipoly (ADP-ribose) antibodies were shown to correlate with clinical activity better than either anti-ds DNA or ss DNA antibodies.

Synergy between IgG and monoclonal IgM antibodies in antibody-dependent cell cytotoxicity

Hybridoma-derived mouse monoclonal IgM anti-ox erythrocyte (ORBC) antibodies, which differed in their ability to exhibit complement-mediated cytotoxicity, direct agglutination and sensitization of indicator cells for detection of receptors for IgM on erythrocytes, failed to mediate antibody-dependent cell cytotoxicity (ADCC) by human K cells. Polyclonal rabbit IgM anti-ORBC antibodies were also incapable of mediating ADCC. However, one of the IgM monoclonal antibodies studied (clone 100) was highly efficient in synergizing with IgG in ADCC, especially when the E rosette-forming enriched fraction was used as a source of effector cells. This synergy was greater after overnight incubation of the lymphocytes and was partially blocked by human IgM. Since all the monoclonal antibodies studied bound efficiently to target ORBC as determined by the additional binding of 125I-labeled anti-k antibodies, the synergy did not appear to be due to a quantitative difference in the binding capacity of the antibodies. That the synergistic effect of purified clone 100 IgM was not due to heterophile IgG antibody was indicated by its sensitivity to reduction and lack of binding to a protein A column. The data are discussed in terms of the possible in vivo relevance of IgG-IgM synergy to immune protection, especially during the development of a primary antibody response when limiting amounts of specific IgG antibodies could be made more effective with the more abundant IgM antibodies.

Synergy between IgG and monoclonal IgM antibodies in antibody-dependent cell cytotoxicity

Hybridoma-derived mouse monoclonal IgM anti-ox erythrocyte (ORBC) antibodies, which differed in their ability to exhibit complement-mediated cytotoxicity, direct agglutination and sensitization of indicator cells for detection of receptors for IgM on erythrocytes, failed to mediate antibody-dependent cell cytotoxicity (ADCC) by human K cells. Polyclonal rabbit IgM anti-ORBC antibodies were also incapable of mediating ADCC. However, one of the IgM monoclonal antibodies studied (clone 100) was highly efficient in synergizing with IgG in ADCC, especially when the E rosette-forming enriched fraction was used as a source of effector cells. This synergy was greater after overnight incubation of the lymphocytes and was partially blocked by human IgM. Since all the monoclonal antibodies studied bound efficiently to target ORBC as determined by the additional binding of 125I-labeled anti-k antibodies, the synergy did not appear to be due to a quantitative difference in the binding capacity of the antibodies. That the synergistic effect of purified clone 100 IgM was not due to heterophile IgG antibody was indicated by its sensitivity to reduction and lack of binding to a protein A column. The data are discussed in terms of the possible in vivo relevance of IgG-IgM synergy to immune protection, especially during the development of a primary antibody response when limiting amounts of specific IgG antibodies could be made more effective with the more abundant IgM antibodies.

Inhibition of lymphocyte capping and transformation by propranolol and related compounds

1 The effects of propranolol on phytohaemagglutinin (PHA)-induced transformation of murine T lymphocytes and capping of anti-IgG on the surface of murine B lymphocytes have been examined. 2 A 50% inhibition of transformation was observed with 10(-5) M propranolol, whereas a higher concentration, of the order of 10(-3) M propranolol was required to inhibit capping by 50%. The (+)-and (-)-isomers of propranolol proved equipotent in these respects, and the relative potencies of selected analogues of propranolol (alprenolol, oxprenolol, metoprolol, practolol, and sotalol) coincided with their potencies as membrane stabilizers; however, lymphocyte transformation was consistently more sensitive than capping. 3 Similar effects were also seen with quinidine, chlorpromazine and lignocaine, and it was concluded that the inhibition of both lymphocyte functions was due to the membrane stabilizing actions of propranolol.

Cloning and sequence analysis of cDNAs encoding two distinct somatostatin precursors found in the endocrine pancreas of anglerfish

Complementary DNAs for two distinct anglerfish somatostatin peptides (termed I and II) have been cloned in bacterial plasmids and sequenced. The nucleotide sequence for somatostatin I encodes a large percursor peptide (molecular weight 13,300) in which the somatostatin hormones is at the carboxyl terminus. The predicted 14-amino acid sequence for anglerfish somatostatin I is the same as mammalian somatostatin. Somatostatin II is also synthesized as part of a larger precursor (molecular weight 14,100) with the presumptive somatostatin hormone also at the carboxyl terminus. The 14-amino acid sequence of somatostatin II differs from somatostatin I at two internal residues (Tyr in place of Phe 7 and Gly in place of Thr 10). The two different somatostatins may have distinct biological activities. Homologies in the amino acid sequences of the two peptides outside the somatostatin moiety suggest other regions of the molecules have biological functions.

Chemotactic factor-induced membrane potential changes in rabbit neutrophils monitored by the fluorescent dye 3,3'-dipropylthiadicarbocyanine iodide

Rabbit neutrophil leucocytes take up the cationic, fluorescent dye 3,3'-dipropylthiadicarbocyanine iodide (DiS-C3-(5)). Treatment with valinomycin and K+ then produces characteristic changes in suspension fluorescence that indicate that the dye enters the cells in a potential-dependent fashion and that the resting membrane potential lies between -66 and -86 mV. The peptide, N-fMet-Leu-Phe, a potent chemoattractant for neutrophils, added to stained cell suspensions, induces fluorescence intensity changes. These occur over an 8-10 min period. The time course of this response is profoundly affected by the omission of Ca2+ from the medium. When this ion is present (1.26 mM) a small, transient increase in intensity is observed, superimposed on a sustained decrease. On the other hand, in the absence of added Ca2+ a large, transient increase is observed. The ED50 for this is 1.1 x 10(-10) M. These changes are not elicited by N-fMet-Phe (10(-9) M) and are inhibited by the antagonist Boc-Leu-Phe-Leu-Phe. However, a component of zymosan-activated rabbit plasma, which is complement-derived, induces identical fluorescence changes that are not inhibited by the antagonist, confirming that neutrophil activation by complement operates through an independent receptor. The fluorescence responses to the chemotactic peptide and the activated-plasma component may be interpreted in terms of changes in neutrophil membrane potential brought about by alterations in cell ionic permeability at an early stage during activation. The transient increase corresponds to a depolarisation that may be associated with a change in Na+ permeability, while the sustained decrease corresponds to a membrane hyperpolarisation.

Subpopulations of human peripheral granulocyes and monocytes express receptors for IgA

Receptors for the Fc portion of immunoglobin on human peripheral blood cells were enumerated by rosette formation with ox erythrocytes sensitized with rabbit IgG, IgA, and IgM. A large percentage of purified polymorphonuclear leukocytes and monocytes were found to express receptors for IgA. These receptors were also found to exist on a significantly greater percentage of lymphocytes than was previously observed. The receptors for IgA were specific, as verified by blocking studies using purified human immunogloblins. In addition, some polymorphonuclear leukocytes and monocytes were observed concomitantly to posses independent receptors for both IgG and IgA. These studies may indicate that IgA can cooperate with monocytes or polymorphonuclear leukocytes through receptors for IgA on these cells and perhaps mediate immune defense on mucosal surfaces. Initial studies on antibody-dependent cellular cytotoxicity suggested that IgA alone is ineffectual in supporting cytolysis by nonactivated human peripheral blood cells.

Evidence for antibody-dependent cell-mediated cytotoxicity by T cells bearing receptors for IgG

Human lymphocyte populations comprising T cells, T depleted lymphocytes, and T cells enriched for, or depleted of, IgG Fc receptor-bearing (TG) cells, were separated using rosette techniques. All lymphocytes were assessed for the ability to lyse antibody-coated chicken erythrocytes and SL2 mouse lymphoma cells. Their activity was compared with that of monocytes and neutrophil-enriched preparations. IgG Fc receptor positive cells within the T population were highly active in both cytotoxicity assays; the activity could not be ascribed to contamination by monocytes or neutrophils. The TG cells forming junctions with the target cells possessed a characteristic ultrastructure.

Parathyroid hormone release is not associated with acute sympathetic arousal in goats

Physiological activation of the sympathetic adrenomedullary (SAM) axis following both thermal and non thermal stress was assessed by changes in serum norepinephrine, glucose and/or protein as well as indices of peripheral blood flow. The occurrence of elevated serum parathyroid hormone (PTH) did not reliably reflect SAM activation as might be predicted from pharmacological studies that document a beta adrenergic receptor mechanism in the parathyroid gland that mediates catecholamine stimulated release of PTH into the circulation. The beta agonist isoproterenol at 1 microgram/min for 60 min did produce a transient increase in serum PTH at 20 min. Overall, the data raise doubts about the physiological significance of the adrenergic receptor in the parathyroid gland. Significant increases in serum PTH of 67% and 109% above basal respectively were seen following ruminal loading with cold and thermoneutral water. Associated with the PTH change were increased serum phosphorus and elevated or constant serum protein and serum total calcium.

Inhibition of dopamine-induced release of growth hormone by thyrotropin-releasing hormone

The effects of thyrotropin-releasing hormone (TRH) and dopamine (DA) on serum growth hormone (GH) levels were examined in the adolescent male baboon. Intravenously administered DA (40 microgram/kg-min-1 for 20 min) raised serum GH and glucose and lowered serum insulin concentrations but caused no increase in blood pressure. Concomitant intravenous infusion of TRH at 2 doses (96 ng/kg-min-1 and 40 microgram/kg-min-1 for 20 min) blocked the DA-induced increase in serum GH. The relatively low effective doses of TRH used to suppress the DA-induced GH increase suggest an interaction with catecholamines at the hypothalamic and/or pituitary to influence GH release.

Characteristics of the effector cells mediating cytotoxicity against antibody-coated target cells. II. The mouse nonadherent K cell

A cell of lymphoid morphology capable of killing antibody-coated chicken erythrocytes was isolated from nonimmune mouse spleen using a combination of carbonyl iron treatment and glass bead column passage. This non-phagocytic effector cell, which is referred to as the nonadherent K (killer) cell, is distinguished from the non-phagocytic myeloid K cell described earlier (Greenberg, A.H., Shen, L. and Roitt, I.M., Clin. Exp. Immunol. 1973. 15:251) by its relatively weak surface adherence properties and low concentration within the mouse spleen. The cell is further characterized by its relatively large size, lack of theta or immunoglobulin determinants, the presence of Mg++-independent complement receptors, affinity for aggregated IgG2 myeloma proteins, inhibition by cytochalasin B and good survival in cell culture. The possible lineage of the cell is discussed.

Characteristics of the effector cells mediating cytotoxicity against antibody-coated target cells. I. Phagocytic and non-phagocytic effector cell activity against erythrocyte and tumour target cells in a 51Cr release cytotoxicity assay and [125I]IUdR growth inhibition assay

Both phagocytic and non-phagocytic effector cells were able to kill rabbit antibody-coated chicken erythrocytes (CRBC) while only non-phagocytic effector cells were active against alloantibody-coated SL2 lymphoma. In addition to the variation in susceptibility of erythrocyte and tumour target cells to various effector cell populations, it was found that different tumour cells can vary markedly in their ability to be killed by non-immune spleen cells in the presence of antibody. It is postulated that both the type of antibody and certain characteristics of the cell membrane are important in determining whether target cells are susceptible to antibody-dependent cell-mediated cytotoxicity detected by the 51Cr release assay. It was also demonstrated that alloantibody-coated P-815-Y mastocytoma, which showed very little evidence of cytotoxicity in the 51Cr release assay, was markedly inhibited in its ability to incorporate [125I]IUdR after incubation with antiserum and non-immune spleen cells. This growth inhibition in the absence of cytotoxicity, or cytostasis, is discussed in relation to the potential mechanisms of target cell damage, and in the light of recent observations (Plata, Gomard, LeClerc and Levy, 1974; Newlands and Roitt, 1975) that cytotoxicity and growth inhibition assays detect different effector cell populations in tumour-bearing animals.

Serum immunoreactive parathyroid hormone and 25-hydroxyvitamin D in patients with uremic bone diseases

Bone histologic parameters and serum iPTH and 25-OHD were measured in 20 patients with end-stage renal failure treated with hemodialysis. By bone histologic criteria, the patients were divided into three groups: mild, osteomalacic, and fibrotic. The increase in serum iPTH was much greater in the fibrotic group than in the mild or osteomalacic groups. In the uremic patients as a group, there were significant correlations between serum iPTH and both percent marrow fibrosis and percent resorbing surface. In the mild and fibrotic groups together, serum iPTH was also correlated with percent forming surface. This and other findings suggested that most of the bone changes in the mild and fibrotic groups could be explained by excess PTH. The difference in bone changes and in serum iPTH between the mild and fibrotic groups could be related to our eariler findings that duration of renal disease was much greater in the fibrotic than in the mild group. The lowest increment in serum iPTH was found in the osteomalacic group. In this group, percent resorbing surface was not increased and there was only a slight increase in marrow fibrosis. Thus in all three groups, serum iPTH appeared to reflect parathyroid status. The cause of the elevated serum iPTH and for the intergroup differences was not apparent inasmuch as serum calcium was normal in all three groups. Serum 25-OHD was significantly elevated in the osteomalacic and fibrotic groups. Because none of our patients had received preparations containing vitamin D, the elevated serum 25-OHD in the osteomalacic and fibrotic groups is consistent with altered vitamin D metabolism in these two groups. There was a direct relationship between percent osteroid area and serum 25-OHD. However, whether or not altered vitamin D metabolism contributed to the mineralization defect in uremic bone disease could not be established.

Characterization of the antibody-dependent cytotoxic cell. A non-phagocytic monocyte?

Death of antibody-coated chicken erythrocytes (CRBC) mediated by nonphagocytic cells was studied. The distribution of effector cells in mouse spleen lymphoid populations after fractionation by velocity sedimentation on Ficoll gradients, isopycnic centrifugation on BSA gradients, and affinity chromatography on Sephadex-linked anti-Fab columns was followed. Cytotoxicity corresponded closely with the distribution of the non-phagocytic monocytes. The cytotoxic effector cell showed similar characteristics to monocytes with respect to size, surface adherence properties and binding affinity for immunoglobulin subclasses.