An Fc receptor-bearing, third population of human mononuclear cells with cytotoxic and regulatory function

Porcine islet cells of Langerhans are destroyed by human complement and not by antibody-dependent cell-mediated mechanisms

In the near future, xenotransplantation of porcine islets of Langerhans might be an alternative in the treatment of patients with diabetes mellitus. However, xenotransplantation of islets of Langerhans in large animals has been shown to result in an exceedingly short graft survival, which suggests that a humoral immune response might play a major role in islet demise. This study was performed to assess binding human preformed antibodies to isolated porcine islet cells (PIC) and to determine the lysis of PIC using human sera in complement-mediated cytotoxicity (CMC) and antibody-dependent cell-mediated cytotoxicity (ADCC) assays. Ten Dutch Landrace pigs were used for the isolation of PIC. Sera from 30 healthy blood donors (1/10 diluted) were used in a 51Cr release assay to assess CMC. Heat-inactivated normal human sera and fresh sera from patients with agammaglobulinemia were used as controls. Binding of human IgM IgG, and IgA antibodies to PIC was tested in an ELISA using isotype-specific secondary monoclonal antibodies ADCC was tested in a 51Cr release assay using normal human sera and sera from newly diagnosed type I diabetics with peripheral blood mononuclear cells as effector cells and PIC as targets. It was found that PIC were recognized by human IgM and IgG preformed antibodies and that fresh human sera had strong CMC activity inducing a percentage-specific PIC lysis of 61 +/- 10% (mean +/- SD) within 60 min. Agammaglobulinemic sera killed 42 +/- 12% of PIC. No significant cytotoxic activity was found in ADCC assays using normal sera or sera from diabetic patients. These results show that all tested human sera lyse PIC via CMC, even in the absence of human antibodies, as concluded from the use of agammaglobulinemic sera. In pig-to-human transplantation, islets may be hyperacutely rejected by antibody-dependent and antibody-independent activation of complement and not by antibody-dependent cell-mediated mechanisms.

Protective effect of a T-cell-dependent immunosuppressive, B-cell-mitogenic protein (F3'EP-Si, or P90) produced by Streptococcus intermedius

The role of a previously described bacterial protein (F3'EP-Si), now designated P90, in the survival of Streptococcus intermedius in the host was investigated, and the immunosuppressive and B-cell-mitogenic effects of this protein were further characterized. C57BL6 mice treated with P90 were about 50 times more susceptible to infection with this bacterium than untreated mice. One of seven splenocytes of C57BL/6 mice were activated by P90. Marked splenomegaly was observed in mice treated with P90, with increased numbers of splenic mononuclear cells and polyclonal immunoglobulin-secreting plaque-forming cells. Peak responses were seen on day 3 for immunoglobulin M (IgM) and on day 5 for IgG, with an isotypic pattern consisting predominantly of IgG2a and IgG2b. When mice were treated with P90 before being primed with sheep erythrocytes, polyclonal immunoglobulin synthesis was accompanied by an ephemeral stimulation of the specific immune response against sheep erythrocytes that was quickly replaced by a dramatic immunosuppression. In contrast, when mice were treated with P90 after being primed, the polyclonal activation was comparatively much less evident and there was no suppression of the specific immune response. Immunosuppression was considerably reduced in mice thymectomized as adults or depleted of CD8+ cells. Adoptive transfer experiments showed that B cells obtained from P90-treated mice were less able to respond to an antigenic challenge, even in the presence of normal T cells, and that T cells obtained from P90-treated mice could actively suppress the specific immune response of normal B cells.

Cells and mediators involved in immunoglobulin synthesis by human circulating mononuclear cells. IV. B cells synthesize but do not secrete immunoglobulins because of a defect in the non-T non-B (null) cells

Null cells (non-T and non-B lymphocytes) have previously been demonstrated to be obligatory participants for immunoglobulin synthesis and secretion by normal B cells in culture. Normal null cells have been demonstrated to secrete a factor, human immunoglobulin synthesis/secretion-facilitating factor (HISFF), which can replace the null cells in the culture. In this investigation, the B cells of an 8-month-old male infant and a 46-year-old male adult who presented with a humoral (antibody) immunodeficiency syndrome synthesized immunoglobulin but did not secrete immunoglobulin after culture with pokeweed mitogen and autologous T cells, monocytes, and null cells. In contrast, the patients' B cells synthesized and secreted immunoglobulin after the addition of allogeneic normal null cells or HISFF to the cultures. The same results were obtained with the cells of the infant and the adult patient tested at monthly intervals for 4 months. The results demonstrate that the patients' T cells, B cells, and monocytes functioned normally and that only the patients' null cells were defective. These findings provide an explanation for the absence of immunoglobulin in the circulation of "non(immunoglobulin)secretors," although they possess normal numbers of circulating immunoglobulin-synthesizing B cells. The defect is in the null cell and not in the B cell and consists of the inability of the null cell to secrete HISFF that facilitates the synthesis and secretion of immunoglobulin by the B cell.

Monoclonal antibody analysis of mononuclear cells in myopathies. IV: Cell-mediated cytotoxicity and muscle fiber necrosis

Cell-mediated muscle fiber injury occurs in inclusion body myositis (IBM), polymyositis (PM), and even in Duchenne dystrophy (DD). Most of the autoaggressive cells are T cells and macrophages, but some are killer/natural killer (K/NK) cells. We here compare the frequencies per 1,000 muscle fibers of endomysial K/NK cells of varying cytotoxicity with those of T cells and macrophages in 8 cases each of IBM, PM, and DD. Two-micrometer serial cryostat sections were analyzed. The Leu-4 marker, present on all T cells and some K/NK cells, and the Leu-7 and Leu-11 markers, present on K/NK cells, were localized by paired immunofluorescence. Macrophages were demonstrated by the acid phosphatase reaction. In IBM, PM and DD, the respective average cell counts per 1,000 muscle fibers were: Leu-4+7- cells (T cells not expressing a K/NK marker)--710, 530, and 59; Leu-4+7+ cells (K/NK cells of low K/NK cytotoxicity)--294, 163, and 13; Leu-4-7+ cells (K/NK cells of intermediate cytotoxicity)--32, 10, and 2; and macrophages--292, 251, and 38. Leu-11+ K/NK cells that have the highest killing activity were virtually absent in all cases. The data suggest a limited role for antigen and major histocompatibility complex unrestricted K/NK cells, as compared with antigen-specific and major histocompatibility complex-restricted T cells, in IBM and PM. Further, the findings cast doubt on the significance of either T cells or K/NK cells in mature muscle in DD.(ABSTRACT TRUNCATED AT 250 WORDS)

A T chronic lymphocytic leukemia with large granular lymphocytes. Phenotype and functions of leukemic cells under in vitro treatment by differentiation inducers

We reported the morphologic, phenotypic and functional characteristics of leukemic cells with natural killer (NK) properties in a case of T chronic lymphocytic leukemia with large granular lymphocytes. These cells were cytologically and cytochemically characterized as phosphatase acid positive large granular lymphocytes (LGL), and presented parallel tubular arrays at the ultra structural level. They displayed a CD2, CD3, CD8, CD11, Leu 7, and Leu 11 positive phenotype while they lacked B cell markers including surface immunoglobulins. In addition, they expressed human leukocyte antigens (HLA) Class I, but no Class II antigens. These phenotypic studies were also performed after cells were cultured in vitro with 12-0-tetradecanoyl phorbol 13-acetate, gamma interferon, 5-azacytidine, sodium butyrate, phytohemagglutinin, and interleukin 2 (IL2). The cell surface markers underwent several significant changes. Among them we noted a higher percentage of labeled cells with anti-CD6 and CD7 monoclonal antibodies (moAbs), and a positivity with an anti-CD19 (B4) moAb. The leukemic LGL spontaneously developed a NK activity on K 562 tumor cells, which was not affected under the various T and B cells growth factors because they became more sensitive to IL2; but they were also stimulated by a 50-kilodalton (KD) B cell growth factor (BCGF) factor devoid of any T cell proliferation activity. Together these results gave a better characterization of azurophilic granules containing T chronic lymphocytic leukemia, and enabled the documentation of the differentiation of LGL with NK activity.

The effects of adherent cells on measurement of the hyper-responsiveness of rheumatoid B lymphocytes to Epstein-Barr virus

Rheumatoid peripheral blood mononuclear cells show an increased responsiveness to superinfection with Epstein-Barr virus (EBV). We have investigated the role of adherent cells in this hyperresponsiveness using two different methods of adherent cell depletion. Depletion of adherent cells from both rheumatoid and normal mononuclear cells, using either dextran bead columns or plastic petri dishes, produced inconsistent changes in the response of autologous non-adherent cells to EBV. The addition of supernatants of cultured rheumatoid adherent cells also produced an inconsistent change in response although normal adherent cell supernatants increased the responsiveness of autologous non-adherent cells to EBV. The inconsistencies observed are discussed with respect to adherent cell subpopulations present in rheumatoid and normal peripheral blood mononuclear cell preparations when using recognized methods of adherent cell depletion.

Functional analysis of a clonal expansion of Leu 11 positive NK active lymphoid cells

A female patient with an unusual lymphoproliferative disease associated with marked neutropenia has been observed for 36 months. The expanded cell population consists of large lymphocytes, many of which contain large azurophilic granules with acid phosphatase activity. These cells were T3, T8, T11 and Leu 11 positive but lacked the M1, T10, IL-2 receptor and HLA.DR antigens. The majority of these cells (60-70%) were also Leu 7 (HNK-1) positive. Strong natural killer (NK) activity was found in both the Leu 7 positive and negative cell populations. This cytotoxic activity was inhibited by monoclonal antibodies known to inhibit NK activity but was unaffected by antibodies which block T cell and T/NK cell cytotoxicity. Further functional analysis indicated that these cells suppressed normal T cell responses to mitogens, MLC responses and PWM induced B cell immunoglobulin synthesis. No effect on bone marrow progenitor cell growth was demonstrated. Antibody dependent cellular cytotoxic (ADCC) activity was barely detectable despite the presence of the Leu 11 antigen. Southern blot DNA analysis demonstrated clonal rearrangement of the T cell receptor beta gene thereby confirming that this variant of T gamma lymphoproliferative disease was a neoplastic condition.

Killing of human dermal capillary endothelial cells by antibody-dependent cellular cytotoxicity

Damage to the microvasculature occurs commonly in autoimmune diseases affecting the skin. There has been little investigation of immune mechanisms other than immune complex deposition as a major cause of microvascular damage. We have investigated the potential of antibody-dependent cellular cytotoxicity (ADCC) to cause vascular destruction in an in vitro model consisting of human dermal microvascular endothelial cells to which were added antibody and leukocytes. Severe damage was induced by antibody and lymphocytes. Monocytes or neutrophils were not able to mediate cytotoxicity although activated neutrophils caused endothelial detachment. The cytotoxic cells were OKT3-, Leu 11+ and were identified as K cells. ADCC was not inhibited by human serum or aggregated IgG. These results imply that ADCC may have a role in causing the vascular destruction observed in some human autoimmune skin diseases.

Direct antibody rosette-forming reactions using monoclonal markers of lymphocyte subpopulations. Methodology and applications illustrated by investigations with rat pan-T antibodies of the CAMPATH series

A sensitive direct antibody rosette assay has been developed for the detection of antigens on the lymphocyte cell membrane. Indicator cells for rosette tests were prepared by chromic chloride coupling of rat or mouse monoclonal IgG or IgM anti-lymphocyte antibodies to untreated or trypsinized bovine red blood cells. The monoclonal antibodies used were reactive with a range of cell surface markers which identify various lymphocyte subpopulations, including T cell antigens, HLA class II (Ia-like antigens), Leu-7 (HNK-1) and VEP 13, a determinant of Fc gamma receptors on large granular lymphocytes. Results obtained by direct rosette formation correlated well with those of parallel tests using indirect immunofluorescent antibodies staining. Several applications of the direct antibody rosetting procedure are described in further investigations with a series of pan-T monoclonal (CAMPATH) antibodies. These include the morphological examination of antibody-binding cells in cytocentrifuge smears, the separation of lymphocyte subsets by density gradient centrifugation, and the use of a rosette inhibition assay to identify monoclonal antibodies binding to the same (or closely associated) epitopes of the lymphocyte cell membrane.

Immunobiology of the expanded T cells in T-cell leukemia and T-gamma lymphocytosis

A review is presented of functional studies performed with the expanded T cells in Sézary syndrome, T-cell chronic lymphocytic leukemia (T-CLL), T-prolymphocytic leukemia (T-PLL), adult T-cell leukemia lymphoma (ATLL), T-cell acute lymphoblastic leukemia (T-ALL) and T gamma lymphocytosis. The immunological and clinical relevance of immunological studies of functional properties of T-cell expansions is discussed.

T-lymphocyte subpopulations in type I diabetes mellitus. A longitudinal study

Monoclonal antibodies were used to characterize peripheral T-lymphocyte subpopulations in 23 patients with type I diabetes mellitus. Initial measurements were made at diagnosis and in 10 of the patients further studies were carried out at 1, 3 and 6 months. T-cell subsets were also measured in 16 patients with type II diabetes, in 16 patients with various autoimmune diseases and in 17 healthy control subjects. At diagnosis, the type I diabetic patients showed a significant decrease in the percentage of cytotoxic/suppressor cells. Both total T-cells and helper/inducer cells were normal. However, when the helper/inducer population was analyzed in the context of islet cell antibodies (ICAs), it was found that those patients possessing ICAs had significantly higher proportions of helper/inducer cells than those lacking them. A significant inverse correlation was seen between the proportions of total T-cells and NK/K cells. At 1 month, the proportions of cytotoxic/suppressor cells returned to normal, whilst the helper/inducer cells showed a transient depression. By 6 months, the only change seen was a significant increase in the percentage total t-cells. No relationship was found between T-cell subset perturbation and metabolic control, as assessed by measurement of hemoglobin A1 (HbA1). The type II diabetic patients showed a significant increase in the percentage of total T cells. The autoimmune patients also showed a significant increase in the proportions of total T-cells; this appeared to reflect an increase in the helper/inducer subset. In the autoimmune patients these findings occurred in conjunction with significant decreases in the absolute numbers of each T-cell subset. It is surmised that, in some cases of type I diabetes, alterations in immune homeostasis may permit autoimmune processes, which lead to cell damage at the onset of diabetes.

Suppressor cell function after intravenous gammaglobulin treatment in adult chronic idiopathic thrombocytopenic purpura

Intravenous gammaglobulin (IVIgG) was given to seven adults with chronic idiopathic thrombocytopenic purpura (ITP). In parallel with platelet count, we studied Con A induced suppressor cell function for the autologous in vitro B cell response, T cell subsets and PAIgG levels, immediately before and 3-4 d after completion of treatment. Before treatment all patients had normal T cell subsets, decreased T suppressor cell function and increased levels of PAIgG. After IVIgG infusions, two patients were unresponsive and neither suppressor cell function nor PAIgG levels varied. In contrast, in the five responding patients we found an improvement in suppressor cell function and a decrease in PAIgG levels, while T cell subsets remained unmodified. Such results were reproducible in three patients after a second series of gammaglobulin infusions. Our results support the hypothesis that IVIgG infusion, apart from its effects on the reticuloendothelial system, may modulate the immune response by enhancing suppressor T cell function.

Natural cytotoxicity of human lymphocytes against equine target cells in vitro

Human lymphocytes displayed a frequent natural cytotoxicity (NK) in vitro against normal equine dermal fibroblasts (ED) and against equine tumour cells of a virus-containing cell line (Mc-1). Similarly, human normal sera contained antibodies that induced antibody-dependent cellular cytotoxicity (ADCC) by normal human lymphocytes against the same target cells. Both NK and ADCC varied for different donors. For individual donors, however, cytotoxicity against the two target cells was significantly correlated both in NK and ADCC. For ED there was also a significant correlation between ADCC and NK activity. Both NK and ADCC showed some selectivity as assessed by cold target cell inhibition. Inhibition studies with Fab fragments of anti-human IgG established the involvement of immunoglobulins in the NK reaction. In this context, a marked and mainly immunoglobulin-dependent increase in both NK and ADCC activity against Mc-1 was observed in a laboratory worker frequently exposed to the target cells. The results indicate that variations of natural cytotoxicity in individual donors may sometimes be an indication of an ongoing spontaneous sensitization.

The absence of any effect of methimazole on in vitro cell-mediated cytotoxicity

Two recent studies have reported that antithyroid drugs inhibit killer (K) and natural killer (NK) cell function in vitro, which could be relevant to the changes in these cell populations during treatment of Graves' disease. In contrast to these reports we have found no in vitro effect of pharmacologically relevant concentrations of methimazole (MMI) (100 mumol/l) on (i) NK cell function using K562 cells or MOLT-4 cells as targets, (ii) K cell function using antibody-dependent cytotoxicity assays with L929 cells or thyroid-antigen-coated chick red cells, or (iii) monocyte-dependent cytotoxin-mediated killing of L929 cells. Enhanced cytotoxicity was found with 1 mmol/l MMI in some of these assays but this was not consistent since it occurred only in certain individual cultures. Since we have shown previously that 100 mumol/l MMI inhibits oxygen radical generation, the present results add to the evidence that these radicals are not directly involved in cell-mediated cytotoxicity and do not support the concept that antithyroid drugs have a significant effect on antibody-dependent cell-mediated cytotoxicity in Graves' disease.