Receptors for immunoglobulins on resting and activated human T cells

Activation-dependent expression of low affinity IgG receptors Fc gamma RII(CD32) and Fc gamma RIII(CD16) in subpopulations of human T lymphocytes

Receptors for IgG (Fc gamma R) are expressed by small subpopulations of peripheral blood T lymphocytes. Our studies demonstrate that T lymphocytes can be induced in vitro to express two different low-affinity Fc gamma R. Mitogen activation of peripheral blood T lymphocytes obtained from eight healthy individuals leads to considerable augmentation of the Fc gamma RIII+ (CD32) T cell subpopulation. The highest percentage of CD32 expressing T lymphocytes could be detected after three days of activation. The T cell subpopulation which transiently express the CD32 antigen, encompasses CD4+ and CD8+ cells. Molecular cloning of the CD32 antigen by reverse transcription and polymerase chain reaction demonstrates that activated human T lymphocytes express the Fc gamma RIIIb2 isoform. The percentage of the Fc gamma RIII+ (CD16) T cell subpopulation was significantly increased only in the lymphocyte populations obtained from three out of eight volunteers immediately after mitogen activation. However, during short-term cell culture the CD16 expressing CD8+ T cell subset increased in the T cell population from all individuals investigated. During this time, the IL-2 receptor alpha-chain (CD25) expression level decreased as a function of time. In contrast to the CD8+CD16+ T cells, the percentage of the non-MCH-restricted CD56+CD16+ T cells was not influenced by mitogen activation and time of cell cultivation. We could show that CD16 in T cells is able to mediate a stimulus leading to proliferation of the CD8+CD56-CD16+ T cells but not that of the CD56+CD16+ T cell subset. This discrepancy cannot be explained by the expression of different Fc gamma RIII isoforms, because both T cell subsets express Fc gamma RIIIA alpha, as we demonstrate in this report.

Chronic lymphoid leukemias: recent advances in biology and therapy

There exists a wide variety of lymphoid leukemias derived from B and T lymphocytes. These diseases have distinct immunologic and biologic features as well as varied responses to therapeutics. The most common lymphoid leukemia is chronic lymphocytic leukemia (CLL) which is a clonal proliferation of a subset of B cells expressing the CD5 antigen. Prolymphocytic leukemia is usually derived from B cells and shares some features with CLL but is clearly a distinct entity. Hairy-cell leukemia is a B cell malignancy that is uniquely responsive to a variety of biologic and chemotherapeutic agents. Waldenström's macroglobulinemia is a B cell malignancy that secretes immunoglobulin M (IgM) and may present with the hyperviscosity syndrome. Other B cell malignancies that less commonly present as leukemias include non-Hodgkin's lymphomas such as follicular lymphoma or mantle zone lymphoma. Multiple myeloma may rarely present or evolve into a plasma cell leukemia, typically in far advanced disease. T cell malignancies that may present as chronic lymphoid leukemias, and in the past have often been referred to as T cell chronic lymphocytic leukemia, are large granular lymphocytic leukemia, adult T cell leukemia/lymphoma, Sézary cell leukemia and rare cases of non-Hodgkin's lymphoma that are T cell derived and may present or evolve into a leukemic phase. There is also a rare T cell counterpart of prolymphocytic leukemia. Distinguishing these diseases is critical for optimal care of these patients.

The immunoglobulin M heavy chain constant region gene of the channel catfish, Ictalurus punctatus: an unusual mRNA splice pattern produces the membrane form of the molecule

The immunoglobulin (IgM) heavy chain constant region gene of the channel catfish, Ictalurus punctatus, has been cloned and characterized. The gene contains four constant region domain-encoding exons (CH1 to CH4) expressed in the secreted form of the immunoglobulin, and two exons encoding the transmembrane (TM) domain utilized in the lymphocyte membrane receptor form of the immunoglobulin. The sequence of a cDNA clone encoding the 3' region of the message for the membrane receptor form of the mu chain indicates that the TM1 exon is spliced directly to the CH3 exon, and not into a site within the CH4 exon, as occurs in the mammals, a shark and an amphibian. This unusual pattern of splicing, which produces a membrane heavy chain that is characteristically smaller than the secreted heavy chain, may be common to all teleost fish.

Expression of receptors for IgA on mitogen-stimulated human T lymphocytes

This study demonstrates that activation of human peripheral blood mononuclear cells (PBMC) by the T cell mitogens phytohemagglutinin (PHA) and concanavalin A (Con A) induces the expression of receptors for IgA without addition of IgA to the culture medium. Cells bearing receptors for IgA were determined by indirect immunofluorescence using human secretory IgA and fluoresceinated goat anti-human IgA or goat anti-secretory component antibodies. Among freshly isolated PBMC, 4.7 +/- 1.7% of T cells, 12.7 +/- 12.5% of B cells and 14.4 +/- 7.6% of monocytes were found to be IgA receptor positive. In unstimulated PBMC cultures the percentage of IgA receptor-positive cells slightly increased at 48 h and was more elevated after 7 days. In Con A-stimulated cultures 24.3 +/- 18.5% of the cells expressed receptors for IgA after 48 h. Then, the number decreased and rose again thereafter. PHA stimulation induced an increase of smaller magnitude with similar kinetics. Induction of receptor for IgA on activated T cells was demonstrated by double-labelling experiments showing more CD8+ than CD4+ cells with receptors for IgA among Con A-activated PBMC. Furthermore, PHA or Con A stimulation of B cell-depleted PBMC suspensions resulted in a marked increase of cells bearing receptors for IgA. Expression of these receptors was down-regulated by recombinant interferon-gamma (250 units/ml) and by prostaglandin PGE2 (100 nM) both on unstimulated and mitogen-activated PBMC. The receptor for IgA was distinct from the asialoglycoprotein receptor and did not cross-react with the poly-Ig receptor of epithelial cells. It was concluded that, in the absence of inducing exogenous IgA, T cell mitogens trigger the expression of receptors for IgA. Therefore, T cell activation is associated with the down-regulation of receptors for IgM and the increased expression of receptors for IgG, IgA and IgE.

Surface markers of human lymphokine-activated killer cells and their precursors. Analysis at the population and clonal level

Lymphokine-activated killer (LAK) activity was first analyzed on PBL populations fractionated on the basis of the expression of T11 or T3 antigen. LAK cell precursors were found to be present in both T11+ and T11- populations, but only in the T3- cell fraction. The generation of LAK activity in highly purified T3- populations of PBL was not accompanied by expression of T3 antigen during a 5-day culture period. LAK activity was next analyzed at the level of limiting dilution clonal microcultures. T11+T3- and T11+T3+ cells, cloned under optimal culture conditions, gave a frequency of proliferating cells of approximately 1 cell in 1.25 for T11+T3+ and 1 cell in 10 for T11+T3- cells. Clones were screened for their ability to lyse fresh ovarian carcinoma cells and K562 target cells. The majority of LAK clones were derived from the T11+T3- cells; moreover, most of the clones derived from these cells displayed LAK activity. Clones displaying LAK activity lysed a panel of fresh or cultured tumor target cells, but failed to lyse PHA-activated lymphoblasts. Surface marker analysis indicated that all the clones had maintained the original T11/T3 phenotype. Whereas 2 T3+ selected LAK clones expressed the T8+T4- phenotype, only 1 out of 9 T3- clones was T8+T4-, all the others lacking both T4 and T8 antigens.

Canine cyclic hematopoiesis: alterations in T lymphocyte subpopulations in peripheral blood, lymph nodes, and thymus of gray collie dogs

Cyclic hematopoiesis (CH), also called cyclic neutropenia, is an inherited disorder known to occur in both humans and gray collie dogs. Previous reports have provided ample evidence to suggest that lymphocyte activity and regulatory mechanisms may be abnormal in CH. The present study examined the lymphocyte populations of several lymphoid compartments of gray collie dogs. The percentage of B lymphocytes in the lymph nodes of CH dogs was significantly increased whereas that of null lymphocytes was decreased. The percentage of T lymphocytes did not differ between CH and normal dogs, however, the proportions of T lymphocyte subpopulations were significantly different. The levels of T lymphocytes expressing IgGFc receptors (T gamma) in the thymus, lymph nodes, and peripheral blood were significantly increased; whereas the levels of T lymphocytes expressing IgMFc receptors (T mu) were significantly decreased. The percentage and absolute numbers of T gamma and T mu lymphocytes cycled in CH dogs. The percentage and absolute numbers of neutrophils were greatest when that of T gamma lymphocytes was reduced. The cycles of monocytes and T gamma lymphocytes occurred in close association and a linear relationship between the levels of these cells was observed both in terms of percentage (r = 0.62; P less than 0.01) and absolute number (r = 0.67; P less than 0.05). The percentage of T gamma and T mu lymphocytes were inversely correlated (r = -0.68; P less than 0.01).

Antibody dependent cellular cytotoxicity mediated by HLA-class II specific monoclonal antibodies

The ability of mouse monoclonal antibodies (MoAbs) directed against HLA-class II molecules to mediate in Antibody Dependent Cellular Cytotoxicity (ADCC) was investigated. The results indicate that both MoAbs to monomorphic and polymorphic HLA-DR and DQ determinants are able to mediate ADCC in an antigen specific manner. However, not all antibodies mediate ADCC to a similar extent. Furthermore, antibodies were identified that appeared to mediate ADCC in an HLA-DR haplotype dependent fashion. These results indicate that the inhibition of HLA-class II specific proliferative responses by anti-class II MoAbs may be influenced by ADCC directed against class II positive stimulator cells.

Lymphocyte subsets at different stages of subacute sclerosing panencephalitis: a study with monoclonal antibodies

Lymphocyte subsets in cerebrospinal fluid (CSF) and peripheral blood were studied using monoclonal antibodies, in patients with subacute sclerosing panencephalitis, eight of whom were at stage 2 and seven at stage 4. Eighteen subjects affected with non immunological diseases constituted the controls. Regardless of the stage, patients with subacute sclerosing panencephalitis had lower percentages of OKT3+ (pan-T) cells in both CSF and peripheral blood, with an increase of OKIa+ cells (B cells, macrophages and active T cells) in peripheral blood. A difference was found in the proportion of OKT4+ (helper-inducer) and OKT8+ (suppressor/cytotoxic) cells in relation to the stage, the most striking finding being a significant decrease of OKT8+ with an increase of T4/T8 ratio in peripheral blood at an early stage.

Allocation of the suppressive activity of normal peripheral blood lymphocytes induced by diffusion chamber culture and Con A stimulation to the G2 phase of the cell cycle

Peripheral blood mononuclear cells stimulated either by diffusion chamber culture or by a high Con A concentration exhibit suppressive activity under conditions where no increase in cell number takes place. Instead an accumulation of large cells is observed which, according to their DNA contents, are classified as cells in the G2 phase of the cell cycle. By elutriation separation the suppressive activity is shown to be confined to this cell cycle phase.

Large granular lymphocyte (LGL) lymphoproliferative diseases: naturally cytotoxic tumors in man and experimental animals

It has recently become clear that in the spleen and blood of both rodents and man that a unique subpopulation of lymphocyte is the mediator of virtually all of the inherent natural killer (NK) and antibody-dependent cell-mediated cytotoxic (ADCC) activity. Because of their large size, eccentric kidney-shaped nucleus and prominent cytoplasmic granules, these cytotoxic cells, termed large granular lymphocytes (LGL), can be readily identified in Geimsa stained cytocentrafuge preparations. Unfortunately, the relatively low numbers of these cells in normal lymphoid tissues has made the detailed analysis of LGL quite difficult. Recently however, a number of investigators have reported both rodent and human leukemias or leukocytosis in which there was an abnormally high number of circulating lymphocytes with either the appearance and/or function of LGL. The present manuscript reviews this literature with an emphasis on the biological and clinical characteristics of this lymphoproliferative disease. Emphasis is also placed on the usefulness of these cells for the detailed analysis of LGL morphology and function.

HLA-DR phenotypes and blood levels of T cell subsets

Blood mononuclear cell and T cell subsets values were analyzed in 53 Sicilian individuals according to HLA-DR phenotypes. The results demonstrate that DR1-positive subjects show a significant increase of blood T cell subsets whereas DR3-positive subjects show a non-significant decrease of these values. These results suggest that gene(s) associated with HLA-DR could be one of the factors which affect blood levels of T cell subsets.

Fc receptor--more answers, more questions

Fc receptors, belonging to the most important surface structures of a number of cells participating in the immune processes, have been intensely studied during the past decade. The present review summarizes the contemporary knowledge of the specificity and heterogeneity of Fc receptors and of factors influencing their expression, and includes some views on their function. In addition, it mentions their relationship to other cell surface structures, expression of Fc receptors during ontogeny of the organism and in certain diseases. Finally, data concerning the isolation and biochemical characterization of the Fc receptor molecule are presented.

Numerical and functional alterations of lymphocytes in human schistosomiasis

Peripheral blood mononuclear cells from 29 Sudanese children heavily infected with Schistosoma haematobium and S. mansoni were examined for lymphocyte subpopulations, for mitogen responsiveness in the absence and presence of interleukin-2 (IL-2), and for natural killer (NK) cell activity. The nutritional status was assessed by anthropometric and biochemical measurements. In comparison with a group of healthy Caucasian individuals the children with schistosomiasis showed a profound alteration of their cellular immune variables, reflecting a severe acquired immunodeficiency syndrome. The T-cell compartment, in particular the OKT4+ helper/inducer subset, was numerically reduced at the expense of an increased B-cell compartment. The patients' OKT4/OKT8 ratios were significantly diminished (median, 1.2; 95% confidence limits, 0.8-1.7) corresponding to a decreased responsiveness to the T-cell mitogen concanavalin A. Since addition of exogeneous IL-2 significantly enhanced the patients' lymphocyte proliferation in response to Con A, a defective IL-2 production was assumed to be at the origin of the impaired mitogenic response in chronic schistosomiasis. With regard to NK cell activity, most patients' lymphocytes failed to mediate significant cytotoxicity against the K562 target cell line, although normal percentages of cells with the NK phenotype (HNK-1+) were present. The results are discussed in view of immunological alterations seen in other parasitic infections with a heavy parasitic load.

Enzyme analysis of autologous rosette-forming cells

Autologous rosette-forming cells (ARFC) have been considered to be post-thymic precursor cells. Since thymocytes and peripheral T lymphocytes differ considerably in lactate dehydrogenase isoenzyme pattern and in activity of the enzymes of the purine metabolism, we investigated the enzyme profile in the ARFC. The L-lactate: NAD+ oxi-reductase analysis showed an isoenzyme pattern that closely resembled the pattern found in peripheral T lymphocytes and was totally different from the thymocytes. The levels of adenosine deaminase and purine nucleoside phosphorylase were identical to those found in the peripheral T lymphocytes and different from thymocytes. In our hands, the ARFC-enriched suspension contained predominantly OKT4+ and T mu+ lymphocytes. We propose that ARFC are a heterogeneous population encompassing all known subsets and cannot be considered a separate homogeneous entity.

Production of alpha-lymphotoxin by human T-cell subsets

Human T cells were isolated from peripheral blood lymphocytes (PBL) and sensitized to allogeneic PBL in a one-way mixed-lymphocyte culture. These sensitized T cells were fractionated on the basis of their possession of Fc receptors for IgG (TG+) or IgM (TM+), or the absence of both IgG and IgM receptors (TG-M-). When restimulated with alloantigen of the same derivation, TG+, TM+, and TG-M- cells yielded almost equal amounts of cytotoxin. Anti-alpha-lymphotoxin serum neutralized most of this cytotoxic activity indicating that alpha-lymphotoxin (alpha-LT) constituted most of this activity. Although TG-M- cells function as effectors in allogeneic cytotoxicity, TG+ cells lyse IgG-coated targets in an antibody-dependent cell-mediated cytotoxic (ADCC) reaction, which has been shown to be mediated in part by alpha-LT. Whether TM+ cells can be cytotoxic is not clear. In addition, freshly isolated human T-cell subsets were stimulated with phytohemagglutinin-P (PHA-P). After PHA stimulation, TG+, TM+, and TG-M- cells produced similar amounts of soluble cytotoxin, which was largely neutralized by anti-alpha-LT. The TG+ cells incorporated less thymidine than the TM+ or TG-M- cells. Likewise, OKT4+ and OKT8+ subsets, isolated with the aid of monoclonal OKT8 or OKT4 antibody and complement, yielded lymphotoxin after stimulation with PHA. It is shown that all T-cell subsets, as defined here, can produce lymphotoxin. Furthermore, depending on the assay system, cytotoxicity can be clearly demonstrated in all of these subsets, except in TM+ cells, where positive and negative results have been reported.

LDH isoenzyme distribution in human T gamma lymphocytes

The lactate dehydrogenase (LDH) isoenzyme distribution was measured in T gamma+ lymphocytes from normal individuals. T gamma+ lymphocytes were obtained from purified T lymphocytes by ox-IgG rosette sedimentation. The B:A subunit ratio was clearly lower in the T gamma+ lymphocytes. Phenotyping of the T gamma+ lymphocytes showed a vast majority of OKT11+, OKM1+, OKT3- lymphocytes. In one experiment, T gamma+ lymphocytes were enriched by OKT3 depletion of T lymphocytes. The low B:A ratio was also found in these cells indicating that the LDH pattern is not the consequence of an in vitro activation by immune complexes. As the T gamma+ lymphocytes were considerably enriched in cells having the characteristics of NK cells according to their phenotyping, morphology and NK cell activity, we may assume that NK cells have a low B:A ratio.

Surface markers on lymphocytes from human cerebrospinal fluid. Identification by monoclonal antibodies

Lymphocyte subpopulations in cerebrospinal fluid (CSF) and peripheral blood (PB) were studied using monoclonal antibodies and the common membrane markers. The results in three groups of patients were compared: 36 subjects with 'non-immunological disorders' (NID), 14 subjects with multiple sclerosis (MS) and 6 with subacute sclerosing panencephalitis (SSPE). It was found that, in patients with NID, (1) 90% of cells were T lymphocytes, reactive with OKT3; (2) the helper/suppressor (T4/T8) ratios were the same in the CSF and the PB; (3) the OKIa1 percentage was lower in the CSF than in the PB; and (4) only a few cells were 'immature', reacting with OKT10. Using the membrane markers (E rosettes, Fc IgG receptors and surface immunoglobulins), on the other hand, it was noted that the majority of cells in the CSF were identified as suppressor T lymphocytes and surface immunoglobulin-positive B cells were less common than the Ia1 marker suggested. There were no significant differences between the CSF results in patients with NID and MS but the OKT3 lymphocytes were reduced in CSF samples from patients with SSPE.

Studies of peripheral blood lymphocytes in Crohn's disease. Circulating activated T cells

Peripheral blood mononuclear cells have been investigated in 43 patients with Crohn's disease (CD) by means of a panel of 4 monoclonal antibodies (UCHT1, UCHT4, 4F2, 5E9). A decrease of total T cells (UCHT1+) (p less than 0.01) and a slight increase of cytotoxic/suppressor T cells (UCHT4+) were observed. Evidence of T-cell activation, as shown by the highly significant increase of 4F2+ and 5E9+ cells, was also found. The latter finding lends support to the concept that cell-mediated immune phenomena are an important feature in CD.

Immunological imbalance in uncomplicated chronic alcoholism

The lymphocyte response to unspecific mitogenic lectins and the frequency of the lymphocytary populations and two subpopulations (DR- and Fc gamma-positive T-cells) as well as the serum immunoglobulin levels were tested. Blood samples were drawn from 15 volunteers with chronic alcoholism, an no clinical detectable correlated diseases and from 8 healthy subjects as controls. An activation of the immune system was found, characterized by an increase of T lymphocytes, DR-positive T-cells, IgA and IgG. Aspects of this activation are discussed.

Ultrastructural characteristics of human T cell clones with various cytolytic activities

Fifteen T cell clones with different (specific, antibody-dependent or natural killer-like) cytolytic activity were derived from mixed lymphocyte culture activated T cells and analyzed for their morphological characteristics and, in some instances, for their surface markers. All of the five cytolytic clones analyzed by electron microscopy possessed numerous electron-dense granules and in some instances multivesicular bodies, with or without an electron-dense matrix, that are the putative precursors of the granules. In addition, light microscopy examination of semithin sections of other ten cytolytic clones showed that the large majority of the cells in each clone had numerous toluidine blue-stained cytoplasmic granules. It is of note that nine clones without detectable cytolytic activity analyzed by electron microscopy did not possess granules and presented the features of large agranular blasts. Ten cytolytic clones were analyzed for different surface markers including rosette formation with sheep erythrocytes (E rosettes), receptors for the Fc portion of IgG or IgM ((Fc gamma R and Fc mu R) and a group of antigens recognized by monoclonal antibodies including Ia, 4F2, OKT8 or OKT4. All the clones were E-rosette+, Ia+ and 4F2+. Expression of Fc gamma R was restricted to the clones active in antibody-dependent cell-mediated cytotoxicity. Expression of OKT8 and OKT4 antigens was variable; in particular, five clones were OKT8+/OKT4-, whereas the other five expressed the OKT8-/OKT4+ phenotype. It is noteworthy that the ultrastructural features of cytolytic T cell clones are similar to those of large granular lymphocytes, known to be the only lymphoid cells in normal peripheral blood which possess cytolytic activity. Thus, it is possible that the presence of electron-dense granules may represent a morphological marker for all human cytolytic lymphocytes.

Circulating T-cell subsets in Graves' disease: differences between patients with active disease and in remission after 131I-therapy

In the present investigation some surface markers in peripheral blood T lymphocytes of patients with active Graves' disease and subjects in remission after 131I-therapy have been studied. We confirmed low TG levels in untreated patients and normal values in treated subjects. Increased percentages of DR+, MLR4+ (activated T cells), and 5/9+ (inducer-helper) T cells were detected in patients with active disease, thus indicating the presence of activated T cells and suggesting increased levels of helper T cells. High percentages of MLR4+ and 5/9+, but normal levels of DR+ were found in 131I-treated subjects. The different distribution of DR and MLR4 positivities on 5/9+ and 5+9-T cells confirm the different meaning of these two markers of the activation state. The imbalance of T-cell subsets found in 131I-treated subjects and the normal values observed in patients with hyperthyroidism due to toxic adenoma indicate that hyperthyroidism per se is not sufficient to explain the T-cell alterations. The possible meaning of these findings is discussed with respect to previous hypotheses on the pathogenesis of Graves' disease.

A rapid micromethod for evaluating T cell subsets in blood using monoclonal antisera

A simple accurate method is described for enumerating T cell subsets in whole blood. The method, which depends on indirect immunofluorescence using biotin-coupled monoclonal antisera and fluorescein-coupled avidin, and propidium iodide for nuclear counterstaining, was compared with the conventional method based on initial separation of lymphocytes by density flotation and exposure to monoclonal antisera. Accurate identification of mononuclear cells in whole blood by nuclear staining with propidium iodide was established. The whole blood method gave numbers for T cell subpopulations generally comparable with those obtained by the conventional method, but slightly higher numbers of Leu2a+ cells were found by the whole blood method, and shown to be higher because of selective loss of Leu2a+ plastic-adherent cells in the conventional method. The whole blood method is quicker, uses only 0.5 ml blood and is economical in use of monoclonal reagents.

Relationship between expression of Fc gamma receptors or Ia antigens and cytolytic activities of alloactivated human T cells

The relationship between expression of Ia antigens or Fc gamma receptors (Fc gamma R) and different cytolytic activities of mixed leukocyte culture (MLC)-activated T-cell populations was studied. Lymphocytes mediating specific lysis of target cells bearing the stimulating alloantigens (CTL) could clearly be distinguished from cells mediating antibody-dependent cellular cytotoxicity (ADCC) in that CTL were Fc gamma R- while cells mediating ADCC were Fc gamma R+. In contrast, MLC-generated natural killer (NK) cells were distributed in both the Fc gamma R- and Fc gamma R+ cell fractions. The presence or absence of Ia antigens did not correlate with any of the cytolytic activities studied. In addition, Fc gamma R- and not Fc gamma R+ cells responded in the secondary MLC. Thus, although Fc gamma R+ cells are generated in large numbers in MLC, they do not appear to play a direct role in specific cytotoxicity nor do they proliferate in response to secondary stimulation. However, their ability, following MLC generation, to mediate NK activity and ADCC, both of which may contribute to in vitro and in vivo lysis of allogeneic cells, might explain their appearance following allogenic stimulation.

Lymphocyte subpopulations in blood and cerebrospinal fluid from patients with subacute sclerosing panencephalitis

Lymphocyte subpopulations in peripheral blood (PB) and cerebrospinal fluid (CSF) from 26 children affected with subacute sclerosing panencephalitis (SSPE) and from 13 controls with various neurological diseases without any immunological implication were examined for surface markers. SSPE patients were found to have significantly lower %s of E-rosette forming cells (RFC) (T lymphocytes) and of EA-RFC (TG lymphocytes, suppressor T cells) in both CSF and PB. No difference was found in EAC-RFC (B lymphocytes) either in CSF or PB. The low EA-RFC values can be explained by genetic factors, immune complexes or virus infection, and they could account for the hypersynthesis of oligoclonal immunoglobulins in the central nervous system. Longitudinal studies performed in 6 SSPE patients during isoprinosine therapy revealed a time-dependent decrement of the %s of E- and EA-RFC in CSF. It cannot be affirmed whether this is related to the disease or to the therapy.

Cell-mediated immunity and immune complexes in the pathogenesis of type 1 (insulin-dependent) diabetes

Evidence for a role of the immune system in the pathogenesis of insulin-dependent (Type 1) diabetes is now plentiful. In the light of the lymphocytic infiltration in the islets of Langerhans, different autoaggressive mechanisms have been suggested in the initiation of B-cell damage. Lymphocytes characterized by cytotoxic properties (K cells) and having receptors for the Fc of IgG are increased in newly diagnosed Type 1 diabetics. Circulating immune complexes are also raised in these patients at the time of clinical diagnosis and there is evidence that K cells bind immune complexes which can modulate the activity of these cells. Here we propose a possible interrelationship between K or Fc gamma receptor+ T lymphocytes and immune complexes which could have a 'key' role in the mechanism of activation of cell-mediated immunity towards B-cells.

Surface markers of human T lymphocytes

Surface markers have been extensively used for the identification and fractionation of different sets of human lymphocytes. Although they have proven useful for the identification of different cell subpopulations and for delineating various stages of T cell maturation or activation, there are a number of limitations in their application that should be carefully considered. In most instances, markers which are reported as defining functional subpopulations are not directly involved in the functional capability to be defined. In addition, a precise correlation between surface markers and cell function is difficult if only a small percentage of the cells in a given subset is involved in the functional activity measured. It is also clear that cell activation and differentiation, or mechanisms of cell fractionation, may affect the expression of some surface markers. Moreover, the assumption that functional activities ascribed to cell subsets or to surface markers in vitro are also operating in vivo may be incorrect. Human T cell surface markers can be grouped in various (as well as overlapping) categories, namely those recognizing the total T cell population, those present on T cell subsets and those expressed only on T cells at a given stage of maturation or as a consequence of cell activation. A more precise correlation between the presence of surface markers and the expression of functional activities can be performed by more complex experimental approaches such as the combined use of various markers and the analysis of surface phenotype of T cell clones with defined functional properties. While the study of T cell clones has clearly pointed out the inadequacy of most markers commonly used for identifying functional subsets of T cells, it provides a valuable tool for identifying new markers that may indeed be selective for a given T cell function.

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.

Inhibition of killer cell cytotoxicity induced by carbimazole in vitro

The in vitro effect mediated by carbimazole (CBZ), a classical anti-thyroid agent on the antibody dependent cellular cytotoxicity (ADCC), low affinity E-rosetting cells (E-RFC) and high affinity E-RFC was investigated using lymphocytes from 11 normal subjects. CBZ at the doses of 250 and 500 mumol/l significantly reduced ADCC in all subjects studied. Low affinity E-RFC--mainly cells possessing receptors for the Fc portion of IgG and expressing cytotoxic properties in the ADCC system--were also significantly reduced following incubation with the same CBZ doses. These results suggest that CBZ, in addition to the known inhibitory effect on thyroid hormone synthesis, may be useful by depressing lymphocyte cytotoxicity in the treatment of autoimmune thyroid disease.

Suppressor T cells in B-cell chronic lymphocytic leukaemia: relationship to clinical stage

In 32 patients with B-cell chronic lymphatic leukaemia (CLL), OKT8+ suppressor T cells were increased in relative (mean 54 +/- 14%; normal mean 34 +/- 6%) and absolute (1.8 +/- 1.6 X 10(9)/1; normal range 0.3-0.6 X 10(9)/1) numbers. OKT4+ helper cells were reduced in relative (mean 53 +/- 15%; normal mean 65 +/- 7%) but not absolute (1.7 +/- 1.4 X 10(9)/1; normal range 0.6-1.4 X 10(9)/1) numbers. Essentially identical results were obtained in treated and untreated patients. There was no significant association between T-cell subset numbers and clinical stage, whether assessed by the Rai classification or the more recent Binet system, although the OKT4+/8+ ratio was slightly lower in advanced disease. The study suggests that the immunoparesis so characteristic of CLL may be attributable to increased suppressor T-cell activity.