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H M Dosch

Publications and source records attributed to H M Dosch.

At least 91 records · Page 5Linked to original sources
PubMed1986

Heterogeneity of EBV-transformable human B lymphocyte populations.

Although most human B cells express receptors for Epstein Barr virus (EBV), few (usually less than 1%) are readily transformed into B lymphoblastoid cell lines after exposure to EBV. Transformable cells previously have been found to be mostly resting B lymphocytes. We recently developed a limiting dilution culture system which permits the growth of EBV-transformed B lymphocytes with high efficiency. Because in this system up to over 30% of peripheral blood- or tonsil-derived B cells respond to EBV, we re-examined the properties of EBV-transformable cells. Frequencies of transformable lymphocytes were determined by Poisson analysis. EBV-susceptible B cells committed to IgM, IgG, or IgA secretion were found to occur in the range of 3 to 27, 0.1 to 6, and 0.1 to 5 per 100 B cells, respectively. Under our culture conditions, a major proportion of the IgM-committed cells derived from large lymphocytes which appeared to have entered the cell cycle. This population contains most of the EBV-responsive cells detected and, therefore, most of the additional cells responding in our culture system. In contrast, precursors of IgG- or IgA-producing lymphoblast lines were small cells with DNA contents typical for the G0/G1 phases of the cell cycle. Anti-immunoglobulin antibodies were used in panning experiments to separate B cell subpopulations which expressed different immunoglobulin isotypes on their surface. In limiting dilution cultures of these purified B lymphocytes subsets, it was found that virtually all precursors of IgM-producing cell lines expressed surface IgM (sIgM) before their infection and transformation by EBV. The "cloning efficiency" of positively selected, large sIgM+ cells approached 100%. In contrast, sIgG or sIgA were found only on cells committed to the production of IgG or IgA, respectively. The expression of sIgD was examined by using sequential panning procedures. Virtually all IgM-committed lymphocytes and a subset of cells committed to IgA secretion were found among the sIgD+ cells. The majority of cells committed to IgA production and all IgG-committed cells were found in the sIgD- B cell population. Our findings indicate that the EBV-susceptible B cell subset of normal lymphocytes is heterogeneous with respect to cell size, cell cycle, sIg determinants, and efficiency of transformation. On the basis of our findings and previous reports, we propose a model in which transformability is a B cell-inherent property. Factors unrelated to the virus but present in our culture system appear responsible for the enhanced vulnerability to viral transformation in some cells which entered into the cell cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1985

Lymphocyte function in human bone marrow. II. Characterization of an interleukin 2-sensitive T precursor-cell population.

In the present study of human bone marrow lymphocytes, we analyze a newly recognized population of T suppressor-cell precursors which are found in marrow only and which have the potential to inhibit immunoglobulin (Ig) production in vitro. Following exposure to interleukin 2 (IL2), suppressor precursors acquire E receptor, T3 determinants, suppressor function, and lectin responsiveness. To distinguish this population within the framework of T-cell ontogeny, it was compared to a previously described population of thymus-dependent helper T-cell precursors which express helper function following exposure to thymus-derived mediators. The two populations are completely distinct and can be separated on density gradients. Suppressor precursors expressed T8 and TAC (IL2-receptor) antigens prior to in vitro induction with IL2. The thymic hormone-dependent cells expressed T4 but not T8 or TAC determinants. In two patients with severe combined immunodeficiency disease (SCID), IL2-responsive precursor cells appeared only late after thymus epithelium transplantation, perhaps best explained by a model in which thymus-dependent differentiation pathways precede, induce, or seed pathways of extra-thymic T-cell differentiation. The large pool size of over 10(11) suppressor and helper precursor cells present in adult bone marrow suggests that these populations may play an important role in immune homeostasis.

Adult↗
PubMed1985

Differential regulation of activation, clonal expansion, and antibody secretion in human B cells.

Limiting dilution analysis, hemolytic plaque assay, and ELISA procedures were used to study the recruitment, clonal expansion, and antibody secretion in human TNP-specific B cells activated in the presence of TNP-ovalbumin (TNP-OA), pokeweed mitogen (PWM), or regulatory T cells. TNP-OA-responsive, hapten-specific PFC precursor cells occupy approximately 0.5% of all sIgM+/sIgD+ B cells in cord blood, bone marrow, peripheral blood, and tonsil. The PWM-responsive, hapten-specific PFC precursor pool is 70 to 90% smaller and does not express sIgD. Antigen-reactive B cells go through a minimum of three divisions in culture (six to nine PFC per clone), and antibody secretory rates of about 10(4) molecules IgM/cell/hr are achieved. In contrast, PWM-induced clone sizes were at least 60 PFC per clone, with antibody secretory rates of approximately 6 to 7 X 10(4) molecules IgM/cell/hr. Addition of high-dose carrier-primed suppressor T cells to limit dilution cultures reduced PFC precursor cell recruitment by up to 99%. However, in the few clones escaping from suppression, both clonal expansion and antibody secretory rates were much higher than in suppressor cell-free cultures, generating 30 to 60% of the antibody secreted in controls but with consequently much more restricted clonal diversity. When limiting dilution cultures were compared with standard microcultures of 2 X 10(5) cells, both clonal expansion and antibody secretory rates were much lower than expected, with a culture efficiency calculated to be 10 to 20% of that in low-density cultures. Our data suggest that the B cell subsets activated by antigen and by mitogen differ in their abilities for clonal expansion and antibody secretion. The hapten-specific and -responsive B cell family is expressed early in ontogeny, and in adults it is distributed evenly throughout the body. These limiting dilution experiments revealed that the primary effect of regulatory T cells is a drastic reduction in clonal diversity, and much less a mere reduction in overall response magnitude.

Aging↗
PubMed1985

Lymphocyte function in human bone marrow. I. Characterization of two T cell populations regulating immunoglobulin secretion.

We analyzed the regulation of immunoglobulin (Ig) production in short-term cultures of human (rib) bone marrow cells. In contrast to blood or tonsil cell cultures, large quantities of IgG and IgA, but not IgM, were secreted by unstimulated marrow cells. The addition of pokeweed mitogen or phytohemagglutinin resulted in the suppression of this Ig secretion. Both mitogens induced the production of high levels of interleukin 2 (IL 2) in marrow cultures, and the addition of IL 2 alone mimicked the suppressive effect of mitogens. Incubation of marrow cells with Epstein Barr virus resulted in enhanced Ig secretion, primarily of the IgM isotype. The addition of mitogen or IL 2 suppressed Ig production in these cultures as well. The mitogen-induced suppression of Ig secretion in stimulated or unstimulated marrow cultures was inhibited by the monoclonal anti-TAC (IL 2 receptor) antibody. Cell separation experiments indicated that the induction of suppressor activity in marrow cultures involved two distinct populations of marrow-resident T lineage cells. The first population responds to activation by mitogens with the production of IL 2. This population has a surface phenotype appropriate for helper T cells. The second T cell population expresses T8 and TAC determinants. These cells acquire suppressor cell activity after exposure to IL 2. The expression of suppressor function does not require additional (e.g., mitogenic) activation signals. The IL 2-dependent marrow suppressor T cells represent a newly recognized T lymphocyte subset. The regulatory pathway delineated may be important for the regulation of antibody formation in bone marrow, the major site of Ig production in man.

Bone Marrow↗
PubMed1985

Reconstitution of nude mouse T cell function in vivo: IL 2-independent effect of human T cells.

The i.p. injection of 1 to 5 X 10(6) heavily irradiated human T lymphocytes resulted in the lasting reconstitution of T cell functions in young mice bearing the nu/nu mutation. IgM and IgG responses to immunization with sheep red cells or ovalbumin, splenic lectin responses, and the expression of easily detectable Thy-1 determinants on up to 20% of spleen cells could be documented for several months after the injection of human cells. Only a narrow cell dose range was effective. Injection of larger cell numbers not only failed to induce immune reconstitution but also resulted in the development of resistance to subsequent treatments. Only mature T cells, but not thymocytes, could induce nude mouse T cell development. Lymphoblasts from one patient with acute T cell leukemia consistently immune-reconstituted nude recipients. These cells were completely unable to produce IL 2 in vitro. In contrast, the IL 2-producing T cell line Jurkat was ineffective, indicating that the abilities to produce IL 2 and to induce nude mouse T cell development are independent. In an extension of earlier models of the nude mouse immune defect, two distinct T precursor cell pools are proposed as the major components of an extrathymic differentiation pathway. As an adequate trigger of differentiation, interaction with thymus-processed T cells guides the development of precursors in the first cell pool towards populating the second IL 2-responsive pool of T precursor cells.

Animals↗
PubMed1983

Diagnosis and classification of severe combined immunodeficiency disease.

The failure to demonstrate normal humoral and cell-mediated immunity (CMI) in patients diagnosed as SCID is seen to reflect the varied pathogenesis of this syndrome. Two major groups of patients have been described, those with or without an associated absence of the enzyme ADA. The heterogeneity of the syndrome is expressed in variable inheritance patterns (particularly defined X-linked or autosomal recessive modes of inheritance), differing clinical presentations, and significant variability in laboratory findings. Some of this heterogeneity of laboratory findings may in fact be contributed to by the high incidence of infection or engraftment of maternal cells in utero. Common to all, however, is the profound deficiency of functional attributes of humoral and cell-mediated immunity. Insight into the biology of this immunodeficiency has advanced steadily in the last decade. Although initially hypothesized to represent a primary lymphoid stem-cell defect, newer technologies to identify and enumerate lymphocyte subpopulations and precursor lymphocytes have revealed the complexity of the disorder. This complexity may now be attributable to a number of abnormalities in the quantitative and qualitative differentiation of these lymphoid stem cells. Functional differentiation of lymphocytes is the result of a progressive and orderly sequence of events. In SCID, lymphocytes of both lineages may be arrested at specific and identifiable stages of maturation, leading to a deficiency of cell-mediated and humoral immunity. In many patients with SCID, the combined immune deficiency may be linked solely to a failure in the stepwise progression of T-cell differentiation.

Acute Disease↗
PubMed1982

Volume regulation by human lymphocytes: characterization of the ionic basis for regulatory volume decrease.

The mechanism of volume regulation in hypotonic media was analysed in human peripheral blood mononuclear (PBM) cells. Electronic cell sizing showed that hypotonic swelling is followed by a regulatory volume decrease (RVD) phase. This was confirmed by both electron microscopy and by cellular water determinations. The rate of regulatory shrinking was proportional to the degree of hypotonicity in the 0.5-0.9 X isotonic range. Cell viability was only marginally affected in this range. The content of cellular K+ decreased during RVD, while Na+ content remained unchanged. Similarly, the efflux of 86Rb (used as a K+ analog) increased upon dilution, whereas 22Na efflux was not altered. 86Rb uptake was enhanced by hypotonic stress and both ouabain-sensitive and -insensitive components were affected. A ouabain-sensitive stimulation was also seen in Na+- free media. Ouabain partially inhibited RVD only if added to the cells hours before hypotonic challenge. A normal shrinking response was observed in K+-free media, and also in Na+-free media when Li+, choline+, or Tris+ were the substitutes. In high K+ or RB+ hypotonic media shrinking was absent and a second swelling phase was observed. Cs+ displayed an intermediate behavior, with shrinking observed at lower dilutions and secondary swelling at higher ones. The direction and magnitude of the response also changed when the external K+ concentration was varied and, with 50 mM K+, no regulatory volume change occurred following hypotonic stress. These findings suggest that RVD occurs largely by a passive loss of cellular K+, resulting from a selective increase in permeability to this ion. In addition, the (Na-K) pump appears to be activated upon cell swelling by a mechanism other than Na+ entry into the cell, but this activation is not essential for RVD.

Cations, Monovalent↗
PubMed1982

Carbamycholine modulation of E-rosette formation: identification of nicotinic acetylcholine receptors on a subpopulation of human T lymphocytes.

We previously suggested that a population of T-suppressor cells carries acetylcholine receptors which may be involved in the regulation of the immune response. To identify cholinergic receptors on human T lymphocytes, we investigated the effects of carbachol, a cholinergic agonist, on E-rosette formation. Preincubation of normal human peripheral blood cells with carbachol resulted in a 30-40% reduction in numbers of E rosette-forming cells. Carbachol-induced inhibition of E-rosette formation was dose-dependent, temperature dependent, and reversible. The drug effects appeared to be mediated through a nicotinic acetylcholine receptor since d-tubocurarine (but not atropine) abrogated its activity. The expression of nicotinic receptors on a subset of human T cells may play an important role in the pathogenesis of certain diseases such as myasthenia gravis.

Animals↗
PubMed1982

Carbamylcholine modulation of E-rosette formation. Effect of plasmapheresis in myasthenia gravis.

Myasthenia gravis may result from a reduction of available acetylcholine receptors at the neuromuscular junction, likely secondary to the presence of anti-acetylcholine receptor antibodies. Since T lymphocytes appear to carry a similar nicotinic acetylcholine receptor, we investigated the capacity of T cells from patients with myasthenia gravis to bind sheep erythrocytes. In addition we determined the effect of carbachol, a cholinergic agonist, on E-rosette formation, and the role of myasthenic serum in modulating these responses. Two groups of patients were identified; one with normal numbers of E-rosettes forming cells (E-RFC) and the other with significantly reduced numbers. The majority of patients with myasthenia had a reduced number of carbachol-sensitive T cells. Incubation of their serum (or the IgG fraction) with normal T cells led to a reduction in numbers of E-RFC, particularly of the carbachol-sensitive subset. These effects were blocked by d-tubocurarine and not by atropine. Following plasmapheresis, normal numbers of E-RFC were detected in the patients and the serum inhibitory activity was no longer detected. The data suggest that in parallel to the achievement of some degree of clinical improvement, plasmapheresis may restore some aspects of lymphocyte function.

Adolescent↗
PubMed1981

Failure of T and B cell cooperation during graft-versus-host disease.

Possible explanations for the immune deficiency usually associated with graft-versus-host disease include defective lymphocyte differentiation and active suppressor cell mechanisms. The present observations in a patient with chronic graft-versus-host disease delineate yet another possible mechanism: a failure of successful interaction between competent patient lymphocytes. Thus, helper and suppressor T cells as well as precursor B cells for the generation of specific in vitro plaque-forming cell (PFC) responses were present among patient lymphocytes and could interact normally with cells from four unrelated normal donors and produce PFC responses. In contrast, patient cells failed to interact successfully with each other and generate PFCs. This suggests a highly (self-) specific block in cell interaction that could explain the inability of the patient to mount a PFC response in vitro as well as a number of antibody responses in vivo during this phase of his disease.

Adolescent↗
PubMed1981

Human T cell colony formation in microculture: analysis of growth requirements and functional activities.

A microculture method in methylcellulose has been developed for the study of human T cell colony formation. The technique is simple, reliable, does not require preincubation with lectin and requires small numbers of cells. Colony formation was dependent on the presence of phytohemagglutin-conditioned medium, a T colony precursor cell (TCPC), and a "helper" or accessory T cell. Plating efficiency was increased 10-fold in the presence of irradiated feeder cells. Progenitors of the T colony cells were identified in peripheral blood, tonsil, and spleen but not in thymus or thoracic duct. They were isolated in the E-rosetting, theophylline-resistant, Fc-IgG-negative cell populations. In peripheral blood the frequency of TCPC and accessory cells, the T colony forming unit, was estimated to be 8 X 10(-3). Colony cells proliferated in response to lectins and allogeneic cells. Forty to 80% of the cells were Ia-positive and stimulated both autologous and allogeneic mixed lymphocyte responses. They were incapable of mediating antibody-dependent cytotoxicity. In contrast, they were effective in assays of spontaneous cytotoxicity but only against certain target cells. This method for the analysis of T colony formation should prove valuable in the functional analysis of T cell subsets in immunodeficiency states or the transplant recipient.

Animals↗
PubMed1981

Role of adenosine deaminase in the early stages of precursor T cell maturation.

The role of adenosine deaminase in the initial stages of precursor T cell differentiation was examined in patients with adenosine deaminase deficiency. Incubation of precursor T cells from adenosine deaminase-deficient patients directly in contact with thymic epithelial monolayers induced receptors for sheep erythrocytes (E rosettes). Pretreatment of these monolayers with erythro-9-(2-hydroxy-3-nonyl) adenine, an inhibitor of adenosine deaminase, prevented differentiation only of adenosine deaminase-deficient T cell precursors, and this could be restored by providing adenosine deaminase following the incubation with thymic epithelial cells. These studies indicate a role for adenosine deaminase in the earliest stages of T cell differentiation.

Adenine↗
PubMed1980

Inhibition of suppressor T-cell development following deoxyguanosine administration.

The expression of immunodeficiency in patients with specific purine enzyme defects indicates a crucial role of the purine salvage pathway in the acquisition and expression of normal immune function. One current hypothesis links the failure of normal lymphocyte development in these diseases to the accumulation of deoxynucleotide triphosphates. In our studies of human in vitro IgM responses, we observed that antigen-induced T-suppressor cell activity was abrogated in the presence of micromolar concentrations of deoxyguanosine (dGuo). In contrast, more than 1,000-fold higher resistance to dGuo was found for both noin-proliferative T-helper cell activity and the differentiation and proliferation of the precursor B lymphocytes for direct haemolytic plaque forming cells (PFC). To determine whether these observations could have in vivo relevance, we monitored the generation of murine T-suppressor cells, capable of abrogating a primary IgM response. It was found that dGuo (but not guanosine) selectively inhibited the in vivo development of T-suppressor cells.

Animals↗
PubMed1980

Characterization of lithium effects on two aspects of T-cell function.

Cell surface receptors receive, transduce and relay a variety of environmental signals. These phenomena, which have been extensively characterized in non-lymphoid cells, also appear to play a crucial role in dictating the degree of lymphocyte responsiveness. The nature of these regulatory events is only beginning to be unraveled but the adenylate cyclase-cyclic AMP axis appears to be one of the important controlling systems. Lithium appears to be as important a modulator of lymphocyte responsiveness as previously shown for a variety of other cells and the mechanism of action, in general, is consistent with its role as a putative blocker of adenylate cyclase activation. Indeed, lithium may exert its role as a regulator of lymphocyte responsiveness by acting on specific lymphocyte subpopulations. Direct proof for this is still wanting and consideration of its capacity for action as an imperfect substitute for normal extra- or intracellular cations or on the physiochemical state of the plasma membrane is necessary. Nevertheless, these studies indicate the validity of using lithium for assessing the role of the lymphocyte adenylate cyclase-cyclic AMP system in the generation and expression of regulatory signals leading to modulation of the immune system.

Animals↗