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B Rocha

Publications and source records attributed to B Rocha.

At least 73 records · Page 4Linked to original sources
PubMed1988

Limiting dilution analysis of interleukin-2-producing mature T cells. Interleukin 2 secretion is an exclusive property of L3T4+ lymphocytes.

Evaluation of lymphokine production by individual activated T cells is necessary to characterize their growth requirements. We have studied interleukin 2 (IL-2) secretion by mature T lymphocytes using a high resolution assay system with the following characteristics: (a) a threshold of IL-2 detection 25 times lower than classic IL-2 titration; (b) the ability to discriminate between IL-2 and IL-4 activities; (c) absence of 'in situ' IL-2 absorption; (d) IL-2 production revealed at the single cell level. By this method an average of 10% of spleen cells, and 75% of L3T4+ cells were detected as producers in a concanavalin A (Con A)-dependent T cell activation system. Our results also suggest the complete restriction of IL-2 secretion to cells with this phenotype. Therefore, factors other than IL-2 must play a major role in Lyt 2+ mitogen-driven, helper-independent T cell proliferation.

Animals↗
PubMed1986

Lymphocyte population kinetics in the mouse.

In a normal dynamic equilibrium, at least half of the peripheral T-cell pool is constituted by lymphocytes which have divided 24-48 h previously, and are therefore rapidly renewed. The renewal of peripheral T cells occurs partly by influx of cells from the thymus and, more importantly, by cell division at the periphery. The cyclic pattern of decay observed for T cells after HU treatment suggests the presence of progenitor-descendent relationships within the peripheral T-cell pool. Peripheral progenitors must contain both cycling and non-cycling cells to account for cell recovery after HU administration in ATx mice. T-cell production at the periphery involves both organized (spleen or lymph nodes) as well as non-organized lymphoid tissue (GALT). The latter may in fact provide the major contribution. Expansion of mature T lymphocytes contributes to clonal persistence at the periphery and to the choice of T-cell repertoires. The importance of post-thymic selection of T-cell repertoires is suggested by the considerable expansion potential revealed by peripheral T cells.

Animals↗
PubMed1986

Life span of B lymphocytes: the experimental basis for conflicting results.

Recent claims have challenged the view that most peripheral, mature B cells are long-lived, and propose rates of peripheral decay that are compatible with bone marrow production. This disagreement can only reflect differences in the protocols and methods used to measure peripheral lymphocyte life spans. We have now assessed toxic or other nonselective effects of hydroxyurea treatment on the survival and migration of peripheral, noncycling cells, as well as possible reasons for exaggerated decays of LPS-reactive B cells transferred to LPS nonresponder hosts, the two methods leading to conclusions of short life spans. We also studied general effects on cell survival introduced by either repeated [3H]thymidine injections or the stress associated with surgery, thoracic duct cannulation in particular--methods with which the notion of long life spans had been established. The results failed to show toxic or nonselective effects of hydroxyurea treatments and artificial decays of LPS-reactive cells in adoptive hosts. In contrast, the present experiments demonstrate that both the stress associated with surgery and repeated [3H] thymidine administration profoundly deplete a pool of short-lived B cells, consequently selecting for an apparent higher proportion of long-lived cells.

Animals↗
PubMed1986

Two major classes of mitogen-reactive B lymphocytes defined by life span.

The relative numbers of short- and long-lived mitogen-reactive B cells in the peripheral pool were evaluated by studying the decay of lipopolysaccharide (LPS)-reactive B lymphocytes in LPS nonresponder, histocompatible hosts for periods of up to 3 wk after cell transfer. The results obtained demonstrate the existence of two major classes of mitogen-reactive B cells defined by life span. The "short-lived" cell component comprises about 80 to 90% of the reactive cells and decays with a life expectancy of 18 to 24 hr. The long-lived cell component, with life expectancies of 10 to 20 days, comprises about 10 to 20% of the reactive cells and is preferentially enriched in circulating B cells. The present ratio for short- and long-lived B cells implies a highly dynamic state for the immune system which must be advantageous in the selection of available repertoires.

Animals↗
PubMed1985

The effects of stress in normal and adrenalectomized mice.

Many of the present concepts in lymphocyte physiology were established using experimental protocols involving surgery in cortico-sensitive rodents. In the present report we demonstrate that commonly used operative procedures in mice result in a depletion of 50-90% of cells from primary or secondary lymphoid organs 24 to 48 postsurgery. Adrenalectomy, by itself, induces considerable depletion, and does not abolish the effects of stress in lymphocyte populations. These findings indicate that questions concerning the dynamics of production renewal rate and life-span of lymphocytes cannot be investigated by approaches involving surgery in the mouse.

Adrenalectomy↗
PubMed1984

Lymphocyte migration into collagen gels: role of lymph.

In the present investigation we found that the presence of lymph within a 3-D collagen gel potentiates the invasion of mature recirculating lymphocytes into the gel. Preferential accumulation of lymphocytes in lymph-containing gels follows the same rules that apply for both in vitro lymphocyte adhesion to high endothelial venules of frozen sections of the lymph nodes and in vivo lymph node entry of lymphocytes. Furthermore, the results obtained suggest that lymph is chemotactic for lymphocytes. This chemoattractant activity of lymph could be assigned mainly to a protein fraction precipitating in the range of 40-60% concentration of ammonium sulphate. The biological significance of these findings for the selective process of lymphocyte emigration from blood to lymph, across the parenchyma of the nodes, is discussed.

Animals↗
PubMed1984

Effects of hydroxyurea on concanavalin-A-induced T-cell proliferation. Depletion of T-cell growth factor-reactive and -producing T lymphocytes.

The effects of eliminating cycling precursors by in vivo administration of high doses of hydroxyurea (HU) in populations of mouse spleen T lymphocytes were studied by membrane immunofluorescence identifying mature Thy 1+, Lyt 2- and Lyt 2+ cell populations and mitogen-induced T-cell growth factor (TCGF) production or reactivity to TCGF. HU treatment results in a sharp decrease in the total number of T cells in mouse spleen, indicating that about 50% of peripheral splenic T lymphocytes have a short survival time in vivo. This depletion is more marked for Lyt 2+ cells than for Lyt 2- cells. The decay of TCGF-reactive spleen cells after drug administration is similar to that of the overall spleen T-cell population. Conversely, production of TCGF induced by concanavalin A is predominantly affected by HU treatment, indicating a shorter life span of the cell(s) involved in TCGF production.

Animals↗
PubMed1983

T cell subsets in patients with rheumatoid arthritis: reduction of cells with Leu 2A phenotype in patients with serum IgG immunocomplexes.

The distribution of T cell subsets in the peripheral blood lymphocytes of 50 patients with rheumatoid arthritis (RA) and 28 controls was evaluated using the monoclonal anti-human T cell antibodies, alpha-Leu 1, alpha-Leu 2a and alpha-Leu 3a. A reduced number of cells with Leu 2a phenotype was observed in the group of patients with active RA. When patients were classified according to both disease activity and the presence of IgG or IgM immunocomplexes, a good correlation was observed between reduced Leu 2a+ numbers and the presence of IgG immunocomplexes. Patients without serum IC had normal numbers of Leu 2a T cells, independently of the activity of the disease. The significance of these results to the understanding of the aetiopathogenesis of RA is discussed.

Adult↗
PubMed1983

Population dynamics of T lymphocytes. Renewal rate and expansion in the peripheral lymphoid organs.

This study investigated the renewal patterns of T lymphocytes in mice. T cell subpopulations in the thymus, bone marrow, spleen, and lymph nodes of normal, shamthymectomized, thymectomized, and splenectomized + thymectomized BALB/c or C57BL/6 mice were identified with monoclonal antibodies to Thy-1, Lyt-1, and Lyt-2 antigens at different times after the administration of hydroxyurea in a regimen shown to deplete cycling cells. As assessed in control experiments, hydroxyurea was not toxic to noncycling lymphocytes and it had no immediate effect on the numbers of mature peripheral T lymphocytes. The injection of hydroxyurea, however, was followed by a decline of T cell numbers to approximately 50% of initial values 24 to 76 hr later, demonstrating that 50% of peripheral T lymphocytes have a short lifespan and indicating the rapid renewal of T cells at the periphery. Furthermore, differential renewal rates were observed in T cell subpopulations defined both by differentiative Lyt phenotype and spleen or lymph node localization. These findings reveal that although the majority of peripheral T cells are not in cycle, they belong to a rapidly renewing population derived after a short transition time from their dividing precursors. The relative contribution of the thymus and of post-thymic expansion to the renewal of the peripheral T cell pool was also evaluated. The results demonstrate high renewal rates in the peripheral T cell compartment, indicate that post-thymic T cells are competent to undergo considerable expansion, and suggest homeostatic mechanisms that regulate the total numbers of peripheral T cells even in thymectomized individuals.

Animals↗
PubMed1982

Spleen lymphocyte populations in patients with Hodgkin's disease--properties of cells with different densities.

Spleen lymphocytes from five patients with Hodgkin's disease (HD) type mixed cellularity and five normal controls were studied. An increased percentage of 'null cells' was observed in three out of the five patients studied. The two other patients had increased percentage of T lymphocytes. Lymphocytes from spleen with HD had a decreased ability to respond to suboptimal concentrations of T cell mitogens. When these cells were fractionated in a discontinuous density gradient a subpopulation of cells, unable to respond to Con A, was recovered from the dense cell fractions. The implications of the present findings to the understanding of the physiopathological changes in HD are discussed.

Adolescent↗
PubMed1980

Characterization of rat spleen cell populations. II. Activation by antigens and allogeneic cells.

Spleen cells from BN rats were separated in a discontinuous density gradient. Cells from different fractions were shown to be functionally diverse. Light cells were highly responsive in MLR, generated little killer activity and enhanced syngeneic recipient's IgM and IgG production in response to SRBC. Dense cells were unable to respond in MLR and suppress Ab response. Maximum killer activity was recovered from medium density fractions which were probably mixtures of helper and suppressor cells.

Animals↗
PubMed1979

Characterization of rat spleen-cell populations. I. Cell interactions in the regulation of in vitro response to concanavalin A.

Spleen cells from BN rats were separated in a discontinuous density gradient. Cells from different fractions were shown to be functionally diverse, light cells enhancing DNA synthesis and cell division of the dense cell fractions, while dense cells suppressed DNA synthesis and cell division of light cells. Both these effects were also present in the absence of cell stimulation, were proportional to the number of modulating cells added to the cultures, and totally independent of the magnitude of response of controls. In Con A-stimulated cultures, mitogen dose also influenced the intensity of help and suppression. Both these effects are blocked by cell treatment with cycloheximide and can be mediated by cell supernatants. A T cell seems to be responsible for both helper and suppressor effects.

Animals↗
PubMedDate not supplied

Lymphocytes migration into membrane filters: divergent effects of syngeneic mouse serum and lymph.

In the present paper, the effects of mouse serum and lymph in lymphocyte adhesion versus locomotion was distinguished using the same substrate (cellulose acetate filters) permissive (8 microns) and non-permissive (0.45 microns) to cells. The results presented suggest that serum and lymph have similar effects on lymphocyte adhesion, but behave differently in locomotion assays. The relevance of these findings to the understanding of the role of lymph proteins in the control of lymphocyte recirculation is discussed.

Animals↗
PubMedDate not supplied

The effects of lymph on lymphocyte migration in vivo.

The in vivo administration of syngeneic lymph significantly modified lymphocyte migration in the mouse. When administered intravenously, lymph inhibited cell localization into lymph nodes, an effect that could be mimicked by lymphocyte pre-incubation with lymph in vitro. The unilateral intrafootpad injection of FR2 of lymph did enhance cell migration, both to the draining popliteal node and to the site of injection when compared to the contralateral foot or draining node. Furthermore, the subcutaneous transplant of polyurethane sponges soaked in lymph or serum into both flanks of a mouse led to increased migration and accumulation of cells in the sponges coated with lymph when compared to sponges treated with mouse serum alone.

Animals↗