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Biomedical subjects

M A Marcos

Publications and source records attributed to M A Marcos.

At least 73 records · Page 4Linked to original sources
PubMed1991

Treatment with IL2/vaccinia recombinant virus leads to serologic, histologic and phenotypic normalization of autoimmune MRL/lpr-lpr mice.

We have analyzed the effect of IL2 administered in vivo on both the lymphoproliferation and autoimmune disease progression of MRL/lpr mice. Human IL2 was delivered by infecting MRL/lpr mice with vaccinia virus recombinants at different stages of lpr disease. The results reported here showed that treatment of lpr mice with IL2 mediated: (1) restored normal thymic differentiation illustrated by an expansion of the double positive population accompanied by increased numbers of mature thymocytes; (2) depletion of the peripheral CD3+ CD4- CD8- (DN) T-cell population; (3) normalization in the pattern of TcRV beta gene expression displayed by mature T cells; (4) decreased urine-protein levels and immune complex deposition in the kidney, with a resultant absence of glomerulonephritis; and (5) an increased longevity (from 195 to more than 400 days). We speculate that the dramatic reduction in the abnormally expanded CD3+ DN T-cell population following IL2 therapy might be directly related to the amelioration and/or prevention of autoimmune disease in these mice. Collectively, these results suggest that diseases showing a selective expansion of DN cells should be envisaged as possible targets for the treatment described here.

Animals↗
PubMed1990

All VH11 genes expressed in peritoneal lymphocytes encode anti-bromelain-treated mouse red blood cell autoantibodies but other VH gene families contribute to this specificity.

We have studied the relationship between B cell reactivity to bromelain-treated autologous mouse erythrocytes (BrMRBC) and expression of the VH11 gene family in splenic, peritoneal and pleuropericardial cell populations from normal C57BL/6 mice. B lymphocytes producing antibodies to BrMRBC were selectively enriched or depleted from normal populations by rosette formation with BrMRBC, followed by centrifugation over density gradients. This selection method, based on the presence of functional receptors (membrane IgM), is harmless for the cells and allowed subsequent cloning in agar (colony-forming unit-B). The utilization of the 10 VH gene families was then scored in mRNA colony blot assays. The analysis of greater than 650 anti-BrMRBC clones and greater than 350 VH11-expressing colonies indicates that about half of those antibody reactivities are encoded by VH11 genes. Furthermore, it appears that all VH11-expressing B cells in the peritoneal cavity produce anti-BrMRBC antibodies.

Animals↗
PubMed1990

Ontogenic characterization of thymic B lymphocytes. Analysis in different mouse strains.

We have characterized a population of murine B lymphocytes present in the thymus (TBL). They are a minor subset (0.2%-1% of total thymocytes), present from perinatal periods onwards and constituted by activated cells with a high proportion of Ig-secreting cells. They represent the first B lymphocytes detected that secrete IgG after birth. Functional analysis reveals that the frequency of lipopolysaccharide-responding cells in TBL is 5- to 10-fold lower than in the spleen. TBL from adult mice did not show any significant difference in their VH repertoire expression when compared to peripheral B lymphocytes. Furthermore, we have been able to isolate a subpopulation of B220+IgM-CD3- thymocytes whose putative B cell precursor potential needs to be directly analyzed. These and other findings support the intrathymic resident characteristics of TBL and suggest new ways of elucidating its physiological role in the complex selective processes occurring inside the thymus.

Aging↗
PubMed1990

Inside the thymus, Mls antigen is exclusively presented by B lymphocytes.

The ability to stimulate an Mls-1 mixed lymphocyte reaction (MLR) is predominantly expressed by low density B lymphocytes in the spleen and peritoneal cavity of normal adult mice, and is absent in splenic B cells 1 month after lethal irradiation and reconstitution from autologous bone marrow. Coreconstitution of these mice with normal syngeneic peritoneal cells restores the stimulatory potential of splenic B cells, but sorted CD5+ or CD5- IgM+ lymphocytes from peritoneum are equally good stimulators, suggesting that functional Mls-1 expression may require long life spans and selection. Bone-marrow-reconstituted DBA/2 mice that fail to express Mls-1 antigens in the periphery nevertheless maintain T-cell receptor V beta 6 and 8.1 deletions among the newly formed T cells. These findings led us to directly investigate the Mls stimulatory ability of purified antigen-presenting cell populations inside the thymus. We report here that thymic B lymphocytes seem to represent the only intrathymic cell population able to stimulate Mls-1 MLR.

Animals↗
PubMed1989

Interleukin-2-dependent autocrine proliferation in T-cell development.

Activated T lymphocytes proliferate in response to interleukin-2 (IL-2), which binds to a specific high-affinity receptor (IL-2R). This consists of at least two noncovalently linked polypeptides, p55/IL-2R alpha (Tac) and p75/IL-2R beta. Both molecules bind IL-2 independently, with low and intermediate affinity respectively, but only IL-2R beta is thought to mediate IL-2 signal transduction. Although IL-2R beta seems to be constitutively expressed on resting T lymphocytes, the growth of these T cells is specifically induced by antigenic triggering by the T-cell receptor (TCR), which then results in the transcription of both IL-2 and IL-2R alpha genes. By contrast, activation of the IL-2/IL-2R pathway in the thymus seems to precede the appearance of the TCR, as IL-2R alpha is expressed on T-cell precursors lacking TCR. The basis for IL-2R expression by immature thymocytes, however, remains largely unknown. We show here that IL-2R alpha-negative T-cell precursors constitutively express IL-2R beta and produce their own IL-2. The IL-2/IL-2R beta interaction on these cells induces the expression of IL-2R alpha, leading to high-affinity IL-2R display and cellular proliferation. We suggest that this IL-2-dependent autocrine pathway of growth stimulation plays a key role in the intrathymic development of mature T cells.

Antigens, CD↗
PubMed1989

Isolation and characterization of (gamma, delta) CD4+ T cell clones derived from human fetal liver cells.

Lymphocytes isolated from human fetal liver and expanded in vitro in IL-2-containing media reveal the existence of CD4+ gamma, delta T cells. These cells display differential features of double-negative and CD8+ gamma, delta T cells as well as of CD4+ alpha, beta T cells. Thus, they failed to lyse targets in lectin-mediated killing assays and to perform classical helper functions. These results add new information necessary for a better understanding of the physiological role of the gamma, delta T cells.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Expression of alkaline phosphatase in murine B lymphocytes. Correlation with B cell differentiation into Ig secretion.

Alkaline phosphatases (ALPase) (orthophosphoric-monoester phosphohydrolase, EC 3.1.3.1) are implicated in many biologic phenomena including ossification and differentiation of human neutrophils and choriocarcinoma cells. Another trait, demonstrated by microinjection into Xenopus oocytes, is their ability to block the first mitotic division. Previous work in our laboratory has established that ALPase is also present on murine B lymphocytes activated by either polyclonal mitogens or Th cells. We have now characterized the ALPase present on murine B cells as belonging to the liver-bone-kidney isoenzyme and found it to be implicated in B cell differentiation into antibody secretion. Thus, B cell proliferative responses, elicited either by high concentrations of rabbit anti-IgM antibodies or by LPS in the presence of PMA, are characterized by the lack of both antibody secretion and expression of ALPase activity. In contrast, B cells stimulated to differentiate into Ig-secreting cells by B cell differentiation factors, nearly in the absence of a proliferative response, express high levels of ALPase activity, as did those that were LPS-stimulated. These data showing the association of the ALPase expression with the process of B cell differentiation into antibody-secreting cells are discussed in the context of the possible role that phosphorylation-dephosphorylation mechanism may play in controlling the growth/differentiation rate in the B cell lineage.

Alkaline Phosphatase↗
PubMed1989

Activation of the interleukin 2 pathway precedes CD3-T cell receptor expression in thymic development. Differential growth requirements of early and mature intrathymic subpopulations.

T cell activation induced via the CD3-T cell receptor (TcR) complex, or by triggering of polyclonal antigen-independent pathways, involves both interleukin 2 (IL 2) production and IL 2 receptor (IL 2R) expression and results in T cell proliferation. To assess the potential role of the IL 2 pathway in T cell development, growth and activation requirements of intrathymic T cell precursors were analyzed and correlated with the expression of IL 2R. In contrast to CD3-TcR+ (either CD4+ or CD8+) mature thymic cells, CD3-TcR- CD1-4-8- early prothymocytes constitutively expressed IL 2R and displayed IL 2-mediated proliferation, which was inhibited by anti-IL 2R monoclonal antibodies (mAb). Moreover, prothymocytes developed spontaneous proliferation in the absence of exogenous IL 2, which was also abrogated by blocking of IL 2R with specific mAb. The possibility that both IL 2 production and IL 2R expression are autonomously activated early in T cell development, before acquisition of the CD3-TcR complex, led us to study the implication of alternative pathways of activation at this ontogenic stage. Triggering of the CD2 pathway with mAb against two different epitopes of the molecule (D66 and 9.6/T11(1) induced proliferation of CD3-TcR- prothymocytes in the absence of exogenous IL 2, while proliferation of CD3-TcR+ mature thymocytes required Il 2 supplementation. These data suggest that polyclonal activation of the Il 2 pathway may be selectively operative at early stages of T cell development, being involved in the growth and differentiation of intrathymic T cell precursors.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Further evidence for coelomic-associated B lymphocytes.

Previous observations indicate that "CD5 B lymphocytes" are preferentially clustered in gut-related mesenchymal areas, such as peritoneum, thymus and tonsils. We have now found that pleuropericardial spaces contain an homogeneous population of large-sized, noncycling, nonsecretory B cells, expressing very high levels of surface IgM, little or no IgD, Mac-1 and low levels of B220. This phenotype and the over-representation of some antibody clonotypes suggest that the pleuropericardial cavity contains a pure "CD5 B cell" population. In all mouse strains analyzed, however, many of these cells are CD5-. These findings, together with the common origin of peritoneum and pleural layers in the primitive coelomic cavity, suggest that such B cells differentiate locally from intraembryonic precursors; we propose to designate them as "coelomic", to distinguish them from "stromal", bone marrow-derived B cells.

Animals↗
PubMed1988

Involvement of the interleukin 2 pathway in the rearrangement and expression of both alpha/beta and gamma/delta T cell receptor genes in human T cell precursors.

In this report, we have undertaken the phenotypic, functional and molecular characterization of a minor (less than 5%) subpopulation of adult thymocytes regarded as the earliest intrathymic T-cell precursors. Pro-T cells were immunoselected and shown to express different hematopoietic cell markers (CD45, CD38, CD7, CD5) and some activation-related molecules (4F2, Tr, HLA class II), but lack conventional T cell antigens (CD2-1-3-4-8-). TCR-gamma RNA messages are already expressed at this early ontogenic stage, while alpha and beta chain TCR genes remain in germline configuration. In vitro analyses of the growth requirements of pro-T cells demonstrated the involvement of the IL-2 pathway in promoting their proliferation and differentiation into CD3+ CD4+ or CD8+ mature thymocytes. Moreover, during the IL-2-mediated maturation process rearrangements and expression of both alpha and beta chain TCR genes occurred, and resulted in the acquisition of alpha/beta as well as gamma/delta (either disulphide-linked or non-disulphide-linked) heterodimeric TCR among the pro-T cell progeny.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1988

Immunological consequences of HIV infection: advantage of being low responder casts doubts on vaccine development.

Immunosuppression in AIDS might be due to the immune response rather than to the pathogenicity of the virus. The basis of the immunosuppression could be molecular mimicries involving viral gp-110, CD4 molecules, antibodies, and CD4-acceptor sites. Whether an individual develops auto-immunosuppressive responses or mounts a harmless defence against (or coexists with) the virus follows the general rules of lymphocyte repertoire selection. MHC and V region genes and other polymorphic loci, together with the previous state of the immune system, particularly at early developmental periods, are factors that influence the response. Vaccination against gp 110-HIV might thus protect against infection but at the same time cause auto-immunosuppression and disease.

Acquired Immunodeficiency Syndrome↗
PubMed1988

B cell participation in the recursive selection of T cell repertoires.

Normal BALB/c mice produce 2,4,6-trinitrophenyl (TNP)-I-Ad specific T helper (Th) cells expressing a receptor heterodimer which share with anti-TNP antibodies an idiotope defined by the F6(51) anti-idiotypic antibody. Expression of this Th idiotype is controlled by major histocompatibility complex and immunoglobulin heavy chain-linked genes and results from antibody-dependent selection of T cell repertoires (Martinez-A. et al., Eur. J. Immunol. 1986. 16: 417). We now present evidence for the recursive nature of T----B cell repertoire selection and suggest that perinatal B cells, present in adult peritoneal cavity, operate in the early phases of this process. Thus, the Th idiotype is absent in BALB/c mice which are either suppressed from birth with anti-mu antibodies, or reconstituted with autologous bone marrow after lethal irradiation as adults. Supplementation of bone marrow reconstitution with syngeneic Thy-1-, Ly-1+ peritoneal B cells, however, selects Th cell repertoires that are undistinguishable from normal mice as to expression of the F6(51) clonotype. This effect is lost after depletion of Ly-1+ cells in the reconstituting Thy-1- peritoneal cell population. Interestingly, large in vivo "naturally" activated Ly-1- splenic B cells can also reconstitute Th idiotype expression if they are isolated from normal, but not from athymic, nude donors. However, transfer of normal large splenic T cells to adult nude mice "educates" the splenic "large B cell" compartment in these animals such that they acquire the ability to recursively select, upon transfer to bone marrow reconstituted recipients, the Th clonotype.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Back-stimulation of B lymphocytes binding to helper T cell surface antigens.

Helper T cells directed to B cell surface determinants activate their "targets" into polyclonal antibody production in vitro and in vivo, but B cells which bind to epitopes on the helper cell surface are preferentially induced. Furthermore, "anti-helper" B cell activation also occurs by "back-stimulation", that is even when the responding B lymphocytes are not specific targets for the inducing helper cells, as long as these are simultaneously activated by appropriate interactions with presenting cells. In our experimental systems, this is the only condition where "bystander" activation can be recorded. These findings suggest mechanisms of auto-antibody production associated with unrelated helper cell activity in vivo.

Animals↗
PubMed1988

Presence of an autoantibody against a Golgi cisternal membrane protein in the serum and cerebrospinal fluid from a patient with idiopathic late onset cerebellar ataxia.

Tissue and cultured cells of different species and embryological origins incubated with serum (diluted up to 10,000-fold) or cerebrospinal fluid (CSF) (6-fold dilution) from a 48-year-old female patient with idiopathic late-onset cerebellar ataxia, exhibited a bright specific perinuclear staining when studied by indirect immunofluorescence microscopy. The pattern of the staining was that characteristic of the Golgi apparatus, consisting of a crescent-shaped juxtanuclear reticulum located in the vicinity of the microtubule organizing center. Changes in location and organization of the organelle stained by the patient's serum during mitosis or after incubation of the cells with Colcemid, taxol or monensin, resulted in a disruption of the reticulum that followed the expected patterns for Golgi apparatus. The staining was specifically absorbed with Golgi cisternae-enriched membrane fractions. Finally, dot-immunoblotting studies of membrane and soluble fractions of Golgi cisternae and vesicles showed that the anti-Golgi antibody (AGA) reacted with the cytoplasmic domain of an integral membrane protein contained in the Golgi cisternae. The presence of this unusual autoantibody in an idiopathic late-onset cerebellar ataxia-bearing patient can afford some insights into the pathogenesis of these neurological diseases.

Autoantibodies↗