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Biomedical subjects

T L Rothstein

Publications and source records attributed to T L Rothstein.

At least 91 records · Page 5Linked to original sources
PubMed1989

Isolation of self-recognizing IgG2a monoclonal rheumatoid factors.

Hybridoma cell lines were produced by fusing spleen cells from 11 mice that expressed the lpr mutation to nonsecreting SP2/0 myeloma cells. Five to 20% of the hybridoma cell lines so derived were found to secrete antibodies that recognized autologous IgG2a. Out of 168 anti-IgG2a clones tested, 4 clones produced anti-IgG2a rheumatoid factor (RF) that was itself IgG2a. Two clones recognized self IgG2a while the other two clones each recognized a nonself IgG2a allotypic determinant. These findings indicate that self-recognizing antibodies are a component, albeit a minor one, of the RF repertoire of lpr/lpr mice.

Animals↗
PubMed1988

Anti-Ig antibody inhibits the phorbol ester-induced stimulation of peritoneal B cells.

Peritoneal B cells are stimulated to enter S phase by phorbol esters acting alone, in the absence of a co-mitogen. Anti-Ig antibody inhibited the stimulation of peritoneal B cells induced by phorbol esters and this inhibition was apparent throughout the time course of PMA-induced stimulation. Assessment of inhibition after depletion of Ly-1+ B cells suggested that PMA-induced stimulation of both Ly-1+ and Ly-1- B cells was affected by anti-Ig. Inhibition produced by anti-Ig was substantially reduced after even a brief delay in the addition of antibody to PMA-stimulated B cells. Anti-Ig antibody may counteract early events triggered by PMA within minutes of peritoneal B cell stimulation.

Animals↗
PubMed1988

Peritoneal B cells respond to phorbol esters in the absence of co-mitogen.

B cells obtained by irrigation of the peritoneal cavity differ from splenic B cells in signaling requirements for the initiation of DNA synthesis. Splenic B cells are stimulated to enter S phase by phorbol esters in conjunction with a second signal provided by calcium ionophore; however, splenic B cells are not stimulated by phorbol ester alone. In contrast, peritoneal B cells from NZB and BALB/c mice were stimulated to incorporate tritiated thymidine by each of the phorbol esters, PMA and phorbol dibutyrate, acting alone. Stimulation of peritoneal B cells was apparent when cells were cultured at lower than usual cell densities, and responses were unaffected by coculture with splenic B cells. Responding cells adhered to plastic petri dishes coated with anti-mouse IgM antibody, but were not completely removed by treatment with anti-Ly-1.2 antibody plus C. These results indicate that phorbol esters constitute a complete signal that stimulates some peritoneal B cells to enter S phase.

Animals↗
PubMed1988

Cytochalasin stimulates phosphoinositide metabolism in murine B lymphocytes.

The ability of cytochalasin to alter phosphoinositide metabolism was evaluated in naive, murine splenic B lymphocytes. The generation of total inositol phosphates was stimulated by treatment with cytochalasin D, as was the generation of inositol trisphosphate. The cytochalasin-induced increase in inositol phosphates appeared to depend on interaction with actin, and it was inhibited by phorbol esters. Inositol phosphate production was not stimulated in splenic T lymphocytes. The results suggest that the previously observed increase in intracellular calcium produced by cytochalasin is part of a more generalized signaling event that includes phosphoinositide turnover, and, further, raise the possibility of a functional association between actin and phospholipase C.

Actins↗
PubMed1988

Fluctuations of CD4+ T-cell subsets in remitting-relapsing multiple sclerosis.

Patients with multiple sclerosis (MS) frequently have selective depletion of the CD45R+CD4+ T-cell subset during active phases of disease. To study the relationship between changes in this subset and the onset of objective clinical exacerbations of disease, a longitudinal study was undertaken. Two CD4+ T-cell subsets and two CD8+ T-cell subsets were monitored by two-color immunofluorescence using a fluorescence-activated cell sorter. These subsets of peripheral blood lymphocytes were monitored monthly for one year in a group of 9 patients with remitting-relapsing MS and in 11 healthy age-matched control subjects. Significant changes in the ratio of two CD4+ T-cell subsets (CD45R-/CD45R+) were detected in 7 of 9 patients with MS, but not in any of the control subjects. Of those 7 persons, 4 suffered major clinical relapses substantiated by alterations in the neurological examination. The other 3 suffered minor relapses with subjective clinical abnormalities. All 7 had increased CD4+ T-cell subset ratios (%CD4+CD45R-/%CD4+CD45R+) within the month that new symptoms were reported. Most such increases resulted from a simultaneous depletion in the number of CD45R+CD4+ T cells and an increase in the number of CD45R-CD4+ T cells. One patient suffered a major relapse with no change in the ratio of CD4+ subsets but had a depletion of all CD4+ T cells. There were no consistent changes in any of the other subsets measured. These results indicate that a subgroup of patients with MS have abnormal fluctuations of two CD4+ T-cell subsets, which may correlate with increased disease activity.

Adult↗
PubMed1988

Oligoclonality of rheumatoid factors arising spontaneously in lpr/lpr mice.

Rheumatoid factors (RF) from individual mice of the MRL/lpr and C3H/lpr strains were examined with regard to target specificity and heavy chain class expression. It was found that MRL/lpr-derived RF preferentially recognize IgG2a target antibodies while C3H/lpr-derived RF exhibit a broader range of cross-reactivity. IgM RF represent only a minor proportion of the RF response in both strains. The IgG2a-specific RF produced by the lpr strains were found to consist of relatively equal proportions of IgG1, IgG2b, IgG3, and IgA antibodies. However, most of the RF produced by a single individual expressed the same heavy chain class and antigen-binding specificity. These results indicate that within an individual lpr mouse, circulating RF are derived from extensive expansion of a limited number of antigen-activated precursors.

Animals↗
PubMed1988

Two-step stimulation of B lymphocytes to enter DNA synthesis: synergy between anti-immunoglobulin antibody and cytochalasin on expression of c-myc and a G1-specific gene.

Previously we demonstrated that stimulation of resting murine splenic B lymphocytes with goat anti-mouse immunoglobulin antibody (GaMIg) plus cytochalasin D (CD) led to DNA synthesis; GaMIg and CD added simultaneously, or GaMIg added before CD, induced this response (T. L. Rothstein, J. Immunol. 136:813-816, 1986). Cells similarly treated with GaMIg or CD alone did not enter S phase. Here we have measured the effects of this two-signal stimulation on the c-myc, 2F1, and gamma-actin genes. The expression of these growth-related genes is known to change either during the G0-to-G1 transition or in the G1 phase of the cell cycle. For the 2F1 and c-myc genes, neither the GaMIg nor CD stimulus alone led to a prolonged increase in mRNA levels, whereas GaMIg plus CD allowed for continuous elevated expression of these genes. Furthermore, GaMIg pretreatment rendered expression of the c-myc and 2F1 genes susceptible to subsequent action by CD. In contrast, CD alone was sufficient to produce changes in gamma-actin gene expression. Thus there are synergistic effects of competence- and progressionlike factors on the expression of the c-myc and 2F1 genes, and these effects correlate with the progression of B lymphocytes to DNA synthesis.

Actins↗
PubMed1987

Cytochalasin induces an increase in cytosolic free calcium in murine B lymphocytes.

Cytochalasin promotes the progression of anti-immunoglobulin-treated B lymphocytes to S phase. However, the intracellular events induced by cytochalasin which may mediate signaling for progression have not been elucidated. In this study, the effect of cytochalasin on the level of intracellular free calcium in murine splenic B lymphocytes was assessed by using the fluorescent calcium indicator Indo-1. Cytochalasins A, B, D, and E induced a rapid and sustained elevation of intracellular free calcium. The calcium response to cytochalasin derived largely from the influx of extracellular calcium, although a small, transient elevation in intracellular calcium persisted when the suspension medium was made calcium-free with EGTA, implicating an intracellular source for a portion of the calcium response. Single cell fluorescence studies revealed that cytochalasin elicited a calcium response in most splenic B cells in suspension, indicating that this phenomenon is not restricted to a subpopulation of responding B cells. Phorbol esters inhibited the B cell calcium response to cytochalasin, and an established response to cytochalasin was rapidly and completely reversed by subsequently administered phorbol ester. T cells that lack the cytochalasin pathway showed a markedly diminished calcium response that was only apparent at higher cytochalasin concentration. However, B cells from xid-defective [CBA/N X DBA/2]F1 males, which fail to respond to anti-immunoglobulin plus cytochalasin, showed a calcium response to cytochalasin similar to that of phenotypically normal F1 females. These data, along with the finding that the rise in intracellular calcium occurred in naive B cells as well as B cells previously treated with anti-immunoglobulin, suggest that there is no clear association between the calcium response induced by cytochalasin and the ability of cytochalasin to stimulate progression to S phase. However, this effect of cytochalasin may suggest a connection between actin filaments and calcium influx in B cells.

Animals↗
PubMed1986

Stimulation of murine B cells by the combination of calcium ionophore plus phorbol ester.

The ability of calcium ionophore and phorbol ester to stimulate entry into S phase was assessed during short-term cultures of murine B cells extensively depleted of T cells. Neither ionomycin alone nor PMA alone stimulated DNA synthesis. However, the combination of ionomycin plus PMA acted in synergy to induce initiation of DNA synthesis in murine B cells. A role for protein kinase C was implied by the inability of 4 alpha-phorbol didecanoate to reproduce the effects of PMA. The combination of ionomycin plus PMA also stimulated DNA synthesis in xid-defective B cells.

Animals↗
PubMed1986

Stimulation of B cells by sequential addition of anti-immunoglobulin antibody and cytochalasin.

B cells are stimulated to initiate DNA synthesis by modest doses of anti-immunoglobulin antibody in combination with cytochalasin. The ability of these agents to stimulate B cells in a sequential fashion was evaluated. Anti-immunoglobulin prepared cells to respond to subsequently added cytochalasin, but cytochalasin did not prepare cells to respond to anti-immunoglobulin. Only brief exposure to anti-immunoglobulin was needed to activate B cells for cytochalasin responsiveness; once activated, B cells remained responsive to cytochalasin for hours. The ability of cytochalasin to supply a second signal to activated B cells suggests that the cytoskeleton may be involved in generating or transducing growth-promoting signals for B lymphocytes.

Animals↗
PubMed1986

Inhibition by phorbol esters of antiimmunoglobulin-induced calcium signalling and B-cell activation.

The inhibitory effect of phorbol dibutyrate (PDB) on B-cell stimulation was evaluated using a model in which activation is induced by modest doses of antiimmunoglobulin antibody (anti-Ig) and progression to DNA synthesis is induced by cytochalasin. PDB preferentially inhibited anti-Ig-induced activation and did so during brief (2 hr) preincubation with anti-Ig. Activation was inhibited whether PDB was added before or shortly after anti-Ig. Since activation for cytochalasin responsiveness appears to be mediated by Ca2+, the effect of PDB on the anti-Ig-induced rise in intracellular Ca2+ was evaluated. PDB (and other phorbol esters that activate protein kinase C) inhibited the rise in Ca2+ normally associated with anti-Ig treatment; moreover, PDB reversed an established anti-Ig-induced Ca2+ response. These data suggest that phorbol esters inhibit B-cell activation by interfering with the elevated levels of intracellular Ca2+ produced by cross-linking of surface immunoglobulin by anti-Ig. This could represent a "feedback inhibition" type of response, but it remains to be seen if this occurs under physiological conditions of protein kinase C activation.

Animals↗
PubMed1986

Effects of anti-IgM on mitogen-induced proliferation of human B-lymphocyte malignancies.

Therapeutic trials of anti-immunoglobulin antibody have produced a wide range of responses in attempts to control the growth of human B lymphoid neoplasms. This variability might reflect differences in intrinsic functional characteristics of malignant B lymphocytes that determine susceptibility to anti-immunoglobulin-mediated regulation of growth. To characterize B-lymphocyte malignancies, tissue samples from 24 patients were studied during short-term culture in vitro. Malignant B lymphocytes were stimulated to proliferate by the T-independent mitogens lipopolysaccharide, cytochalasin B, and Staphylococcus aureus that bears protein A. The effects of monoclonal mouse anti-human IgM on mitogen-induced malignant lymphocyte proliferation were then assessed. Mitogen-induced responses of malignant lymphocytes from three patients were abrogated by 2 micrograms/ml monoclonal anti-human IgM. Proliferation was also abrogated by polyclonal goat anti-IgM antiserum but proliferative responses were not affected by control monoclonal antibody. Further study showed that anti-immunoglobulin-mediated inhibition of proliferation was not dependent on Fc-determined interactions, nor was it dependent on the presence of T lymphocytes. These results indicate that a subset of human B-lymphocyte malignancies are susceptible to inhibition of proliferation mediated by anti-IgM.

Antibodies, Anti-Idiotypic↗
PubMed1985

Selective loss of a subset of T helper cells in active multiple sclerosis.

Patients with active multiple sclerosis (MS) have a selective loss of a subset of T helper cells (Th), detectable by two-color fluorescence-activated cell sorter analysis of peripheral blood lymphocytes. By using pairs of monoclonal antibodies to the T-cell subset markers CD4 (Th) and CD8 [T suppressor/cytotoxic cell (Ts)] and the common leukocyte markers Lp220 and Lp95-150, five phenotypically distinct T-cell subsets have been identified in peripheral blood: two CD4+ Th cell subsets and three CD8+ Ts cell subsets. The frequencies and absolute numbers of these five populations were measured in patients with active and inactive MS and were compared with those in healthy age-matched controls and in patients with other neurologic diseases. A high frequency of patients with active MS (80%) had a selective reduction of one Th subset (CD4+ Lp220+) compared with normal controls (P less than 0.001) or patients with inactive MS (P less than 0.001). Three patients examined sequentially had a further loss of the Lp220+ Th subset as disease activity progressed. The proportion of two Ts subsets was also abnormal in patients with active MS, but this defect was not restricted to that group. Total Th and Ts cell frequencies and Th/Ts ratios were not significantly different between patient and normal control groups. Thus, two-color analysis of T-cell subsets may be a more sensitive indicator than conventional single-marker assays of abnormal immune status in MS patients.

Adolescent↗