Characterization of human T-cell subpopulations as defined by specific receptors for immunoglobulins

Expression of Fc mu receptors on human natural killer cells

Fc receptors for IgG (CD16) have been described as the only type of immunoglobulin receptor on large granular lymphocytes (LGL). However, the ability of natural killer (NK) cells to mediate antibody-dependent cellular cytotoxicity (ADCC) in the presence of monoclonal or polyclonal IgM and the inhibition of NK activity by highly purified IgM could not be explained on the basis of FcR for IgG. In order to directly assess the expression of Fc receptors for IgM (Fc mu R), NK cells were treated with human polyclonal IgM, and its binding was visualized by a direct anti-globulin rosette assay with identification of rosette-forming LGL on Giemsa-stained smears. The data indicated that a high proportion of LGL (up to 68%) were Fc mu R-positive cells. However, this percentage varied depending on the IgM preparation (polyclonal or monoclonal), the indicator reagent used for the rosette assays, and the cell preparations studied. Two-color flow cytometry of human nonadherent lymphocyte preparations confirmed the presence of CD56+IgM+ cells, which represented from 43 to 78% of CD56+ cells. Flow cytometry was also performed using highly enriched preparations of human NK cells (the mean percentage of CD3-CD56+ cells was 84%). Up to 88% of purified NK cells bound FITC-labeled monoclonal IgM at a saturating concentration. By indirect immunofluorescence, from 34 to 62% of NK cells purified from the peripheral blood of normal donors were able to bind polyclonal IgM. Similar results were obtained with LGL from a patient with NK lymphoproliferative disease. Thus the presence of Fc mu R on a majority of human NK cells was demonstrated by different techniques, using unseparated peripheral blood mononuclear leukocytes, purified normal NK cells, and also LGL from a patient with NK lymphoproliferative disease.

Isolation and characterization of Hofbauer cells from human placental villi

Hofbauer cells are a major cell type of the human placental villous core and they are particularly numerous at the beginning of pregnancy. In the present study we describe a method suitable to obtain HC suspensions in a highly purified form. These suspensions have been analyzed for surface markers using a battery of monoclonal antibodies. Of all the surface markers used, Hofbauer cells were only positive for 4F2, LeuM2 and LeuM3 monoclonals which mainly detect cells of the monocyte-macrophage lineage. Hofbauer cells were consistently negative for HLA-DR antigens, C3bR and T- or B-cell markers. Hofbauer cells appeared capable of phagocytosing latex beads, adhering to and spreading over plastic surface and secreting lysozyme. In contrast, they failed to originate an efficient respiratory burst in response to appropriate stimulation. Hofbauer cells were positive for ANAE with a perinuclear localization of the enzyme activity, but consistently negative for peroxidase. These observations suggest that they share a number of features with cells of the monocyte-macrophage lineage and yet have some distinctive properties.

Immunoglobulin-specific suppressor T cells

This article has considered evidence that supports the occurrence and functional importance of suppressor T cells that are directed to B cell targets. Cells with these features have been demonstrated in experimental animals and in humans. The designation "suppressor" comes from the serologic phenotype of these cells as well as from their functional property of noncytotoxic inhibition of B cell function. Distinct suppressor T cells with these properties have been identified that effect antigen-, idiotype-, isotype-, and allotype-specific suppression of B cell function. While such cells had been suspected from earlier studies of normal immune responses, the development of monoclonal B cell models using tumor cells has provided a means to readily detect these suppressor T cells and to investigate the mechanisms by which they mediate their effects. Tumor models have proved to be powerful tools in the effort to identify and analyze the elements that underlie the complexity of immune responses. Combined with the insights provided by molecular genetic approaches and flow cytometry, functional and responsive lymphoid tumor cells are being used with increasing frequency to address basic immunoregulatory issues. An important family of suppressor T cells with B cell targets are those that express surface Fc receptors, elaborate immunoglobulin-binding factors, and appear to participate in the regulation of immunoglobulin heavy chain class expression. In addition to their importance in the regulation of heavy chain class expression during normal immune responses, alterations in FcR+ T cells in a number of disease states may provide clues that will lead to a better understanding of disorders of immune regulation.

Relationship between structure and T-lymphocyte maturation in human thymomas. Enzyme histochemical and immunohistological studies

Twenty-six human thymomas were studied in an attempt to correlate their morphological appearance with the type and degree of T-lymphocyte maturation, as determined by acid alpha-naphthyl-acetate esterase (ANAE) activity and immunological analysis. Four normal human thymuses were used for purposes of comparison. Two morphological patterns were identified in the thymomas. The distinction was based largely on similarities between the neoplastic epithelial cells and normal cortical and medullary epithelial cells, and on the relative proportions of epithelial cells and lymphocytes. By these criteria "medullary" and "cortical" patterns were identified. In several thymomas both patterns were present in the same tumor ("mixed-type pattern"), producing alternating dark cortical-like areas and lighter foci of medullary differentiation. A good correlation was found between the two patterns and the phenotype of the T-associated lymphoid component. ANAE activity, which was completely lacking in normal cortical thymocytes, was almost absent in the phenotypically immature T-cells of cortical-type thymomas. By contrast, in the medullary-type thymomas, T-cells showed immunological features in common with medullary thymocytes. This was characterized by strong ANAE activity in the majority of cells with a staining pattern corresponding to that of peripheral T-lymphocytes. In addition, most of the proliferating epithelial cells in medullary-type thymomas stained strongly with anti-cytokeratin and anti-epidermal-type keratin antisera. In the mixed-type thymomas the epithelial cell morphology and the immunohistochemical and enzymic features of the T-cells were found to be closely related to the respective cortical--or medullary-like areas. It was concluded that the various characteristics of normal thymic cortex and medulla studied are also present in thymomas. In particular, in medullar-type thymomas the presence of many of the features of normal thymic medulla, such as a squamous cell component, macrophages and interdigitating reticulum cells, may constitute a microenvironment which operates actively in T-cell education. This may account for the functional activities, characteristic of peripheral T-lymphocytes, which T-lymphocytes attain in these thymomas.

Immunoelectron microscopic identification of human NK cells by FITC-conjugated anti-Leu-11a and biotinylated anti-Leu-7 antibodies

Human natural killer (NK) cells have been reported to express various surface antigens. The majority and the most functionally potent NK cells are Leu-11a (NKP-15) positive cells. Only a small number of functional NK cells express Leu-7 (HNK-1) antigen. In the present study, we have established techniques for immunoelectron microscopic identification of NK cells by mouse monoclonal FITC-conjugated anti-Leu-11a and biotinylated anti-Leu-7 antibodies. Ficoll-Hypaque-isolated peripheral blood lymphocytes (PBL) were reacted with the specific antibodies before or after fixation in a 1% glutaraldehyde/1% paraformaldehyde fixative. Prefixation labeling of viable cells with the antibodies was carried out at 4 degrees C or 37 degrees C. Cells prelabeled with anti-Leu-11a antibody were reacted with secondary antibodies either before or after fixation. Anti-Leu-7 antibody was stained directly via an avidin-biotin-peroxidase (ABC) system, anti-Leu-11a antibody was stained indirectly by the ABC immunoperoxidase procedure via a biotinylated anti-mouse IgG secondary antibody or by a 10 nm or 40 nm colloidal gold-labeled anti-mouse IgG antibody. Results indicate that Leu-7 antigen could be localized by incubation with the specific antibody either before or after 20 min fixation; however, Leu-11a antigen was totally abrogated following the same fixation procedure. The Leu-11a antigen was well stained by the methods of prefixation labeling of cells with anti-Leu-11a antibody and incubation with a biotinylated secondary antibody and the ABC system after fixation. With respect to colloidal gold labeling, better results were obtained when cells were reacted with the gold-labeled antibodies immediately after incubation with anti-Leu-11a antibody but before fixation. Ultrastructurally both Leu-7 positive (+) and Leu-11a positive (+) cells shared common ultrastructural features associated with large granular lymphocytes. Using the above described techniques, we found approximately 2-5% Leu-7+ and 9-15% Leu-11a+ cells in the PBL of healthy donors. The overall results suggest that Leu-11a antigen is more sensitive to glutaraldehyde/paraformaldehyde fixation than Leu-7, since it can be localized only by prefixation labeling procedures; the ABC immunoperoxidase procedure is an ideal technique for labeling NK cells for light and electron microscopic enumeration; the immunogold method provides an adequate technique for labeling NK cells which are designated for ultracytochemical studies.

Maturation of chronic lymphocytic leukemia B cells: correlation between the capacity of responding to T-cell factors in vitro and the stage of maturation reached in vivo

Circulating malignant cells from 15 patients with B-cell chronic lymphocytic leukemia (B-CLL) were examined by the electron microscope (EM) and tested for their capacity to produce immunoglobulin (Ig) molecules using endogenous labeling techniques in vitro. In agreement with previous observations, B-CLL clones from various patients could be subdivided in three distinct groups: immature (type 1) clones, that comprised mainly small resting lymphocytes which synthesized, but degraded Ig of the secretory type intracellularly; mature (type 3) clones consisting mainly of cells with an extended Golgi apparatus and numerous strands of rough endoplasmic reticulum (RER) that secreted Ig molecules; and clones (type 2) at an intermediate maturational stage. When stimulated with T-cell supernatants that contained T-cell replacing factor(s) (TRF), type 3 and, to a lesser extent, type 2 clones differentiated further and secreted increased amounts of Ig. This maturation was not observed when type 1 clones were stimulated with the same supernatants. However, these cells were not incapable of further maturation since they could differentiate in response to phorbol ester (TPA). The present data reinforce the concept that different CLL clones undergo a process of maturation in vivo that may be arrested at different levels and demonstrate that the various clones respond differently to physiological stimuli depending upon the level of maturation already reached in vivo.

Fc gamma-receptor-bearing, non-B lymphocytes in human peripheral blood: cytophilic immunoglobulin binds almost exclusively to large granular lymphocytes

Cytophilic IgG (CYT-Ig) has previously been reported to bind to both the "TG" (E+, Fc gamma R+) and "L" (E-, Fc gamma R+) subsets of non-B lymphocytes in human peripheral blood. Present investigations show that IgG-binding cells, as detected by a sensitive antiglobulin rosetting reaction, are contained almost entirely within the large granular lymphocyte (LGL) subpopulation, and that fewer than 5% of other non-B lymphocytes acquire IgG from serum. Cell membrane-bound IgG sterically blocks the reaction of LGL with sheep red blood cells and therefore influences the proportions of these cells characterized as TG (E+) or L (E-) lymphocytes. Although the majority of TG lymphocytes are LGL, a further subpopulation of E+, Fc gamma R+ cells are detectable under particular test conditions. Unlike LGL, these lymphocytes do not react with rabbit IgG-coated ox RBC (EAG) in saline, but will form EAG rosettes when the reaction is enhanced in the presence of Ficoll. These Fc gamma R+ cells are mostly of typical small-lymphocyte morphology and do not bind detectable amounts of CYT-Ig, nor do they express the monoclonal antibody-defined VEP 13 determinant associated with Fc gamma R on LGL.

Discrimination between innate and cytophilic immunoglobulin on human peripheral blood lymphocytes: analysis by the direct antiglobulin rosette-forming reaction

Bovine red blood cells linked to polyclonal or monoclonal anti-immunoglobulin antibodies are used in the direct antiglobulin rosetting reaction to detect surface-Ig on human lymphocytes. The sensitivity of this test is markedly increased by pretreating the red cells with trypsin. Enzyme-treated red cells, coupled to anti-human Fab or anti-light chain antibodies, react not only with innate Ig on B lymphocytes but also with smaller amounts of passively adsorbed, cytophilic Ig on up to 25% of freshly prepared peripheral blood (non-B) lymphocytes. In contrast, trypsinized red cells carrying anti-Ig isotype-specific antibodies react exclusively with B cell surface-Ig. Cytophilic Ig is abnormally firmly bound to lymphocytes separated on Ficoll-Hypaque at 20 degrees C or below, and is released very slowly during 3 h or more at 37 degrees C in vitro. Lymphocytes are free of detectable cytophilic Ig when isolated on Ficoll-Hypaque at 37 degrees C, and very little Ig is retained by non-B cells in suspensions purified on Percoll which, unlike Ficoll, does not increase Ig binding affinity. These lymphocyte separation procedures are recommended as a preliminary to B cell assays by sensitive antiglobulin techniques.

A simple procedure for freezing and storing lymphocyte panels in trays

Lymphocytes from different donors may be frozen in Terasaki trays by a simple procedure. This method provides the tissue typing laboratory with a readily available panel that can be routinely used to test for lymphocytotoxic antibodies sera from patients waiting for kidney transplant, transplanted patients and polytransfused individuals. The advantage of this procedure is that expensive programmed freezing apparatus is not required.

In situ characterization of cell infiltrates in human dental periapical granulomas. 2. Demonstration of receptors for the complement components C3b and C3d

The inflammatory cell infiltrates in human dental periapical granulomas were studied through the demonstration of receptors (R) for fragments C3b and C3d of the complement component C3, C3bR and C3dR were detected in cryostat sections by the closed chamber hemadsorption technique. Sheep erythrocytes sensitized with rabbit IgM antibody and coated with human C3B or C3d were used as indicator cells. Of the 62 granulomas studied, 23 showed strong or moderate C3bR activity, and weak C3dR activity was detected in 5 out of 25 specimens. The C3bR activity was abolished by treatment with 0.25 mM periodic acid, indicating that carbohydrate is a part of the C3bR. Using an antiserum to C3R as first layer in indirect immunofluorescence experiments, the C3R was localized to cell membranes. The low C3dR activity indicates that a minor part of the mononuclear cells in the human periapical granulomas were B lymphocytes.

The same human alloreactive T cell clone can help both B lymphocytes and specific cytotoxic precursors

Human alloreactive proliferating T cell clones have been compared for their capacity to provide help for B cell activation and the generation of a specific cytotoxic response. The results demonstrate that, when triggered by the relevant alloantigen, the same T cell clone can induce a strong polyclonal B cell activation and serve as the only source of helper cells for the generation of a specific cytotoxic response by any source of CTL precursors against any stimulator cell present in culture.

Lymphocyte subsets and immune complexes in long-standing diabetic patients: relation with the presence of microangiopathy

Subsets of peripheral T lymphocytes by monoclonal antibodies and circulating immune complexes by two different methods were evaluated in 36 long-standing diabetic patients, 19 Type 1 (insulin dependent) and 17 Type 2 (non-insulin dependent). In all patients the presence of microangiopathy was assessed by retinal fluoroangiography, albuminuria and creatinine clearance. In patients with Type 1 diabetes a significant decrease of total T and of T cells with helper phenotype (T4), together with an increase of T cells with suppressor/cytotoxic phenotype (T8), were observed. No significant modifications in the percentage of T lymphocyte subsets were detected in patients with Type 2 diabetes. Immune complexes were found to be significantly increased in Type 1 compared with Type 2 diabetic patients. Patients with very high levels of T8+ cells did not have detectable immune complexes and had no evidence of microangiopathy. By contrast, patients with normal levels of these cells were found to have raised immune complexes and showed retinopathy of varying degree. The results of this study indicate that: (1) a relationship exists between cells with T8 phenotype, some immune complexes and the presence of microangiopathy; (2) the decrease of T4+ cells in Type 1 diabetics with long duration of disease may be responsible for the known susceptibility to infections in these patients.

Enhancement of erythrophagocytosis by cyclophosphamide

The effect of cyclophosphamide (Cy) on erythrophagocytosis carried out by peritoneal exudate cells (PEC) was evaluated. The results indicate that the treatment of BALB/c mice with a single high dose of Cy (200 mg/kg) increases the capability of PEC to ingest sensitized sheep red blood cells. Cy not only increases the percentage of PEC with engulfed erythrocytes, but also augments the activity of individual phagocytes. This effect is exerted upon both mononuclear and polymorphonuclear cells and is probably due to the activation of receptors for the Fc fragment of IgG on PEC membranes, as unsensitized sheep erythrocytes are not phagocytized. Considering that Cy is one of the most used alkylating agents in treatment of immunological disorders and cancer chemotherapy, this enhancing effect on phagocytosis may be important in the regulation of host defense mechanisms.

B-lymphoproliferative disorders: a proposed unified pathogenetic pathway

The clinical features of lymphoproliferative diseases associated with paraproteinemia are briefly reviewed and correlated with current immunologic concepts in an effort to clarify the pathophysiology of B-lymphocyte disorders. B-lymphocyte maturation proceeds in a predictable manner from the Pre-B cell to the formation of idiotype specific plasma cells and memory B-lymphocytes. The immunoglobulin isotype produced by the mature plasma cell is determined by a site specific process of gene switching which proceeds from mu to alpha production. Lymphoproliferative diseases are the result of disordered B cell maturation and their clinical features can be explained by identifying the locus of the maturational defect.

Spontaneous and alloantigen-induced cytotoxicity by human T-lymphocyte subpopulations

Freshly isolated human T lymphocytes were separated into two subpopulations on the basis of their ability to form E rosettes after treatment with the phosphodiesterase inhibitor, theophylline. T cells that retained the ability to form E rosettes (T-res cells) and those that failed to form E rosettes (T-sens cells) were assayed for natural killer (NK) cell activity against 51Cr-labeled K562 tumor cells and for the ability to proliferate and kill allogeneic cells in mixed-lymphocyte culture (MLC). T-sens cells were highly enriched for NK activity. In contrast, T-res cells exhibited much less activity than either T-sens or unseparated T cells (T-sens greater than unseparated T cells approximately equal to unseparated PBL approximately equal to non-T cells greater than T-res cells). T-sens cells were poorly responsive to allogeneic cells in proliferation assays and demonstrated greater levels of cytotoxicity against allogeneic cells than T-res cells. T cells stimulated with allogeneic lymphocytes for 7 days were cytotoxic for K562 targets while comparably stimulated non-T cells and T cells cultured with medium were not cytotoxic. Cold target inhibition experiments suggested that within the T-sens subset there are overlapping populations which mediate cytotoxicity against K562 and allogeneic cells. These studies demonstrate that freshly isolated human T cells are composed of heterogeneous populations which differ in their ability to mediate NK and to generate cytotoxic T lymphocytes in culture.

Expression of a receptor for sheep erythrocytes by B lymphocytes from a chronic lymphocytic leukemia patient

A patient with a B-cell chronic lymphocytic leukemia, whose lymphocytes also formed rosettes with sheep red cells, is described. The B-cell nature of the malignant lymphocytes was determined by surface marker analysis, and cytochemical and ultrastructural studies. The lymphocyte membrane immunoglobulin (IgG1K) did not have anti-sheep red cell activity and was not responsible for the binding of sheep erythrocytes to the leukemic cells as shown by (i) the failure to inhibit rosette formation with anti-immunoglobulin reagents and (ii) the different sensitivity to proteolysis of the membrane immunoglobulin and the sheep erythrocyte receptor. The malignant lymphocytes expressed a receptor for sheep erythrocytes similar to that of normal T cells since they stained with monoclonal antibodies directed against the sheep red cell receptors. Furthermore these antibodies blocked rosette formation. Endogenous labeling experiments demonstrated that the patient's cells produced IgG both of the membrane and of the secretory type. The latter molecular form was also actively secreted. Ultrastructural studies demonstrated that the malignant clone comprised cells at different maturational stages and with different secretory properties. These findings were confirmed by the analysis of intracytoplasmic acid hydrolases, which are normally expressed at late maturational stages. These data are consistent with the hypothesis that a process of maturation was occurring within the malignant clone.

Circulating T cell subsets in euthyroid Graves' disease

T cell subpopulations recognized by surfaces markers of different functional meaning have been evaluated in 12 female patients with euthyroid Graves' disease and in 2 patients with ophthalmopathy and Hashimoto's thyroiditis. We have used the following markers: i) receptors for Fc fragments of IgG; ii) antigens recognized by the monoclonal antibodies MLR4, 5/9, BT 2/9 (anti-DR). In the 12 patients with euthyroid Graves' disease a marked decrease of TG cells (which proved to exert suppressor function in several in vitro systems) was observed, as previously reported in hyperthyroid Graves' disease. The 2 Hashimoto's patients with eye changes had normal or high TG. 5/9+ T cells (which contain cells with helper activity in vitro), as well as MLR4+ and BT 2/9+ cells (activated T cells) were normal in the majority of patients, but elevated in the 2 Hashimoto's thyroiditis. The observed abnormality of TG cells in euthyroid Graves' disease might be consistent with the hypothesized autoimmune pathogenesis of endocrine ophthalmopathy.

Functional studies on lymphocytes from two siblings with congenital hypogammaglobulinaemia

Two brothers with hypogammaglobulinaemia classified as common variable immunodeficiency (CVID) were investigated for distribution of peripheral blood lymphocyte (PBL) subpopulations, DNA synthesis and plaque-forming cell (PFC) capability of pokeweed mitogen (PWM) activated autologous and allogenic cocultures. Both patients had a decreased absolute number of T cells and normal or elevated levels of surface immunoglobulin (SmIg) bearing cells. Isolated B cells cocultured with autologous or allogeneic 4000 r irradiated T cells responded subnormally to PWM monitored by the 3H-thymidine incorporation in microcultures whereas B cells cocultured with allogeneic untreated normal T cells proliferated normally. PBL from parallel macrocultures of unfractionated or T/B separated patients' cells were not able to produce plaques using a reversed haemolytic protein A assay. Addition of glucocorticoid to unfractionated PBL did not reverse the unresponsiveness. In allogeneic cocultures patients' untreated or 2000 r irradiated T cells induced a normal PFC response. Normal untreated T cells induced a reduced number of IgM- and IgG-PFC from patients' B cells but this response was almost eliminated using irradiated normal T cells. These results demonstrate a primary B cell defect in the patients and indicate an impaired cooperation between patients' B and T cells. Activation of patients' B cells to Ig secretion requires the presence of proliferating T cells.

Survival and PHA-stimulation of gamma-irradiated human peripheral blood T lymphocyte subpopulations

Human peripheral blood T lymphocyte subpopulations were identified and isolated on the basis of their ability to bind IgG (T-G), IgM (T-M), or neither immunoglobulin class (T-null). Lymphocytes were exposed to 0, 0.5, 1.0, 2.5 or 5.0 Gy of 60Co gamma-rays either as a T-cell suspension or as separated T cell subsets. Survival curves, determined 5 days after irradiation, revealed that each subset has radiosensitive and radioresistant portions, and that the T-G cell is the most sensitive subset. Mitotic indices of 48-h cultures showed that the response of unirradiated T lymphocytes to PHA varied greatly among the subsets, the highest indices being obtained for the T-M and the lowest for the T-G cells. With the possible exception of the T-G cells, the subsets are relatively resistant to mitotic effects of gamma-rays. T-G cells suppress the PHA-induced mitotic response of the other T lymphocyte subsets, and this suppressor effect is radiosensitive, being abolished by 1.0 Gy. It is concluded that lymphocytes exposed to greater than or equal to 1 Gy of gamma-rays will have very few dividing B lymphocytes or T-G cells. This together with radiation-induced loss of T-G suppressor action means that the predominant lymphocyte types in mitosis after greater than or equal to 1 Gy are the radioresistant T-M and T-null cells.

Ultrastructure of normal human blood T lymphocyte subsets isolated by cell sorting using monoclonal antibodies. A stereological analysis

In continuation of a previous study, the quantitative fine structural characteristics of the average normal human pan-T lymphocyte and its subsets in the peripheral blood has been established using stereological methods. T cell subpopulations were isolated and identified by means of monoclonal T3, T4 and T8 antibodies and a fluorescence-activated cell sorting machine. Comparative studies on ultrastructural morphology were made between the E-rosetting lymphocyte and the T3-positive cell, both markers of the pan-T cell, and between the functionally different T4- and T8-reactive subsets, defining the helper/inducer and suppressor/cytotoxic T cell subpopulation respectively. No significant differences were recorded between the E-rosetting and the T3+ lymphocyte except for minor deviations regarding the surface of the plasma membrane. In comparison with the T4+ lymphocyte, the T8+ cell showed a larger cell volume and cell surface area and decreased nucleo/cytoplasmic volume and surface ratios. The increase in cell size was the result of greater volumes of residual cytoplasm as well as of intracytoplasmic organelles, such as mitochondria, RER, Golgi apparatus and granules, whereas nuclear parameter estimates were concordant. The structural deviations between the T4+ and the T8+ subsets are discussed in the context of their different functional capacity as helper and suppressor/cytotoxic cells.

Density distribution profiles of T cells: TM, TG and TA cells and response patterns in autologous versus allogeneic MLRs

Discontinuous Percoll gradients have been used to obtain selected human peripheral blood T lymphocytes without having to resort to interactions with immune complexes in the fractionation of Tm, Tg and Ta cells. Here, we could show that Ta cells represent a heterogeneous population with no distinct density profile, in contrast to light (Tg) and heavy (Tm) cells. Enriched, heavy Tm cells could be shown to be excellent responders in allogeneic MLR while failing to react in autologous MLR. In contrast, T cells of light density preferentially respond in autologous compared with allogeneic MLR.

The role of autologous helper and suppressor T cells in the regulation of human granulopoiesis

Helper and suppressor T cells play a physiological role in immunoregulation and possibly in other biological systems. Previous studies have suggested that unfractionated T cells influence human blood cell formation in vitro. Subpopulations of such cells (TM and TG cells) were prepared by immune ox erythrocyte rosetting techniques. Co-cultures were established in semi-solid agar with autologous null lymphocytes as a source of granulocyte-macrophage progenitor cells (CFU-GM). TM(helper) cells produced an increase and TG (suppressor) cells a decrease in the expression of CFU-GM as reflected in the number of GM colonies generated by comparison with cultures of null lymphocytes alone. These data point to a contribution from T lymphocyte subpopulations to the physiological regulation of human granulopoiesis.

Human T cell lines with antigen specificity and helper activity

Human T blasts, obtained by stimulation of peripheral blood mononuclear cells (PBM) with tetanus toxoid, diphtheria toxoid or Candida albicans, were expanded in long-term culture using alternate periods of antigen restimulation and growth in media containing interleukin 2. The cells gave a proliferative response only to the antigen originally used for stimulation. Such as response was strictly dependent upon the presence of autologous but not of allogeneic mitomycin C-treated mononuclear cells. When added to autologous PBM depleted of E-rosetting cells together with the specific antigen, the T blasts induced a polyclonal proliferation and differentiation of B cells. Allogeneic B cells were activated by antigen-stimulated T blasts only in the presence of irradiated mononuclear cells autologous to the responding T blasts. The above responses seemed not to be regulated solely by the release of soluble factors; apparently cell to cell interactions had to take place to obtain an efficient B cell activation.

Analysis of Fc gamma receptors on human peripheral blood leukocytes by flow microfluorometry. I. Receptor distributions on monocytes, T gamma cells and cells labeled with the 3Al anti-T cell monoclonal antibody

A dual parameter flow microfluorometric technique for accurately measuring Fc gamma receptor (FcR) expression on defined subsets of cells within a heterogeneous cell sample was developed. The FcR distribution of human peripheral blood mononuclear cells consists of three distinct peaks. By analyzing cells fluorescently labeled with the 3Al, an anti-T cell hybridoma antibody (using a green-emitting fluorophore) and for FcR (with a red-emitting fluorophore), and by using cell isolation procedures, it was shown that the cells lying within the peak with intermediate FcR density are mainly monocytes, while cells lying within the peaks with highest and lowest (i.e. negative) FcR densities are predominantly T cells. The FcR+ T cells (T gamma cells) express higher levels of the 3Al antigen than other T cells, thus demonstrating the utility of the 3Al hybridoma antibody as a marker for T gamma cells.

Receptors for the third complement component on a proportion of large granular lymphocytes from human peripheral blood

Large granular lymphocytes (LGL) are nonadherent cells with cytoplasmic azurophilic granules, avid receptors for the Fc portion of IgG, and a paranuclear localization of alpha-naphthyl acid esterase or acid phosphatase. LGL constitute the bulk of TG cells (cells with receptors for sheep erythrocytes and for IgG molecules) and null cells (non-T, non-B cells). In the present study we demonstrate that 20-33% of the circulating human LGL express receptors for the third complement component (C3R). When TG cell or null cell fractions from normal individuals or non-T cells from a patient with infantile agammaglobulinaemia (which contained almost exclusively LGL) were rosetted with erythrocytes coated with antibody and complement, a variable number of C3R-bearing cells were detected. Such cells were isolated and analysed further; the great majority of them displayed the cytochemical and ultrastructural features of LGL.

T-cell subpopulations defined with monoclonal antibodies in patients with primary immunodeficiency

Peripheral blood mononuclear cells from 16 patients with common variable immunodeficiency and 4 with selective IgA deficiency were studied for the quantitative analysis of T-cells and T-cell subsets with distinct immunoregulatory properties, using a battery of monoclonal antibodies and the fluorescence-activated cell-sorter. The proportions of OKT4+ cells were decreased and OKT8+ cells were increased in patient groups when compared to normal controls analyzed simultaneously. 14/20 (70%) patients demonstrated a lower OKT4+/OKT8+ cell ratio compared to controls. Imbalance of immunoregulatory T-cells may explain one of the mechanisms of hypogammaglobulinemia in a subgroup of patients with primary immunodeficiency.

A subset of human cells isolated and characterized by monoclonal antibodies

Monoclonal antibodies were induced against leukemic T cells from a patient with chronic lymphocytic leukemia exhibiting natural killer (NK) activity. Two antibodies, termed T811 and M522, reacted by indirect immunofluorescence with distinct sub-populations of normal human mononuclear blood cells. The antibody T811 defines a surface antigen which is restricted to a subset of the T cell lineage. The antigen recognized by the second antibody, M522, is expressed on monocytes and polymorphonuclear leukocytes and, in addition, on 9-17% of nonadherent peripheral blood leukocytes (NAL). It is shown that the total NK activity of NAL is confined to the subset of cells expressing the M522-defined antigen. Moreover, the portion of NK cytotoxicity associated with T lymphocytes is mediated by a subpopulation which is characterized by the simultaneous expression of the T811- and the M522-defined antigens. This population comprises about 4% of NAL and could be isolated to a purity of greater than 85%.

Human thymoma: immunologic characteristics of the lymphocytic component

Several immunologic parameters were investigated in the lymphocytic component of ten thymomas, characterized by a variable degree of lymphocytic infiltration. The majority of thymoma lymphocytes are T-cell in nature, as are lymphocytes from the normal thymus. Lymphocytes from six thymomas with moderate or predominant lymphocytic infiltrates were capable of forming stable E-rosettes, (mean percentage +/- SD: 78.0 +/- 5.2); binding peanut agglutinin (67.3 +/- 8.6); and exhibiting receptors for the Fc-portion of IgM (21.8 +/- 6.0) at percentages that were close to those found in the normal thymus. On the other hand, lower numbers of stable E-rosetting cells (26.8 +/- 8.7), PNA-positive cells (27.5 +/- 12.4), and remarkably higher percentages of cells with receptors for IgM (54.0 +/- 4.2) were demonstrated by the lymphocytic population of four thymomas with scant lymphocyte components. In addition, lymphocytes from tumors with scant lymphocyte components show a higher proliferative response to phytomitogen (PHA), therefore exhibiting immunologic features comparable to those of the more mature pool of normal medullary thymocytes. The observed immunologic similarities between the populations of lymphocytes from thymomas and from the normal thymus gland suggest an exclusively epithelial origin of the thymoma.

Influence of in vivo hydrocortisone on some human blood leucocyte sub-populations. II. Effects on T cell-monocyte cooperation

The effect of in vivo hydrocortisone (OHC) on various in vitro T cell responses was studied in five volunteers. Four hours after the administration of 300 mg OHC intravenously, the T cell response to soluble antigen (PPD) was only slightly depressed - as was the response to alloantigen - whereas the T cell response to autologous non-T cells was nearly abolished. In vivo OHC caused a profound depression of the number of circulating monocytes, but those still remaining in circulation had retained their antigen presenting capacity. In vitro OHC-treatment for four hours prior to PPD stimulation did not affect the antigen presenting capacity of monocytes or the proliferative responsiveness of T Cells.

Human T lymphocytes subpopulation as defined by alloantigens and FC receptors a comparative analysis

Human peripheral T cells were fractionated in accordance to their surface receptors for G or M immunoglobulins and analyzed for their reactivity with alloantisera obtained by planned immunization involving HLA-A and HLA-B compatible individuals. These alloantisera were previously shown to recognized polymorphic structure exclusively expressed on T cells. Although the majority of the alloantisera analyzed reacted with different proportions of both T(M) and T(G) populations, some antisera specifically recognized surface structure restricted to either T(M) or T(G) lymphocytes. The various alloantisera consistently reacted with a fraction only of T(G) and T(M) cells, this indicating that these T cell subsets can be further fractionated in accordance to the expression of the alloantigenic determinants recognized by these antisera.

Regulation of IgG antibody-dependent cellular cytotoxicity in vitro by IgM antibodies

IgM antibodies have previously been reported to either inhibit or induce antibody-dependent lymphocyte cytotoxicity (ADCC). Here we show that human lymphocytes lyse bovine erythrocytes (Eb) in the presence of either IgM of IgG anti-Eb from rabbits. Seven out of 20 IgM preparations (Sephadex G-200) were ADCC-active. IgG-dependent ADCC was inhibited by human IgG but not by IgM. In contrast, IgM ADCC was inhibited by both IgG and IgM. The effector cells in IgM ADCC were a subpopulation of lymphocytes with distinct Fc receptors for both IgG and IgM. Most of them also had sheep erythrocyte receptors. Extensive purification of the ADCC-active IgM antibody preparations indicated that very small amounts of contaminating IgG anti-Eb were responsible for ADCC induction. When purified and ADCC-inactive IgM antibodies were mixed with suboptimal concentrations of IgG antibodies, a strong enhancement of ADCC was found. To achieve enhancement, the two antibody isotypes had to be present on the surface of the same target cells, and the IgM effect was not due to the release of soluble ADCC-enhancing factors. Thus, in this system, IgM antibodies are not capable of inducing ADCC on their own. However, they enhance ADCC by improving the contactual interaction between target cells and a special subset of effector cells.

A major subpopulation of Fc receptor-bearing lymphocytes revealed by rosette formation in dextran media: studies with pig, sheep and rat lymphocytes

Blood lymphocytes from young pigs which formed 9.1 +/-0.7% Fc rosettes (mean +/- S.E., range 4.1-16.0), with rabbit and pig immunoglobulin-coated indicator cells used in optimum conditions in phosphate-buffered saline (PBS), formed 32.6 +/- 1.8% (16.9-44.3) in the presence of 4% dextran (DFc). The proportion of DFc+/Fc+ lymphocytes varied from 2.2 to 5.9 (3.8 +/- 0.3). Compared with the PBS test, in dextran rosettes are formed with more lymphocytes and with red cells coated with less immunoglobulin. Ficoll at 14% gave similar enhancement. Dextran enhancement of Fc rosettes was also observed with sheep PBL, but not with rat thoracic duct lymphocytes. The FC portion of IgG is responsible for both Fc and DFc rosettes. Thus most Fc and DFc rosettes, formed with serum antibody-coated bovine RBC, are revealed by IgG coated but not F(ab')2-coated BRBC, and show dose-dependent inhibition in the presence of free pig IgG (complete at 5-10 mg/nl) but not IgM (up to 2 mg/ml). Separation of lymphocytes on nylon wool suggests that DFc rosettes are formed by B cells and some T cells. Over half of the weak Fc rosette-forming lymphocytes (DFc-Fc) elute in the non-adherent fraction, which contains few B cells, and therefore are a subpopulation of T cells.

Fc receptors on human T lymphocytes: loss of Fc mu and expression of Fc gamma receptors by T cells stimulated in mixed lymphocyte reaction

The consequences of allogeneic stimulation on the expression of Fc mu or Fc gamma receptors were analysed in T-cell populations responding in mixed lymphocyte reaction (MLR). Unfractionated T-cell populations were cultured with a pool or irradiated allogeneic T-depleted cells. The responder E-rosetting cells progressively lost Fc mu and acquired Fc gamma receptors. The change of the original Fc receptor phenotype is not the consequence of a preferential proliferative response of TG versus TM cells but is likely due to a de novo expression of Fc gamma receptors by T cells lacking detectable Fc receptors (T-null) and also to the loss of Fc mu and expression of Fc gamma receptors by TM cells. These data suggest that, after MLR, responder T cells can modify their Fc receptor phenotype.