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Biomedical subjects

J E Layton

Publications and source records attributed to J E Layton.

At least 55 records · Page 3Linked to original sources
PubMed1989

Treatment of chemotherapy-induced neutropenia by subcutaneously administered granulocyte colony-stimulating factor with optimization of dose and duration of therapy.

In patients who have not received extensive prior chemotherapy or radiotherapy, it has been previously demonstrated that granulocyte colony-stimulating factor (G-CSF) abrogated the leukopenia following administration of melphalan (25 mg/m2). This study examined the necessity of a prechemotherapy period of G-CSF administration and the effect of varying the timing and duration of postchemotherapy G-CSF. Initially, patients received 0.3, 1.0, 3.0, and 10 micrograms/kg/d subcutaneously on days 1 to 5 and days 10 to 18. Melphalan was given on day 9. In the next portion of the study melphalan was administered on day 1 and G-CSF, 10 micrograms/kg/d, was administered by subcutaneous infusion on five schedules: (1) days 2 to 13; (2) days 8 to 13; (3) days 2 to 18; (4) days 8 to 18; (5) days -9 to -2 and 2 to 13. G-CSF produced a rapid and sustained elevation in neutrophil levels within 24 hours even when started 8 days after melphalan. This treatment was sufficient to abrogate the neutropenia in patients who had received no prior chemotherapy. It was not necessary to continue G-CSF for more than 7 days. G-CSF did not consistently alter the course of the thrombocytopenia that followed this dose of melphalan. G-CSF was well tolerated, although mild bone pain occurred and was reduced with acetaminophen. One of 22 patients developed cellulitis at an infusion site. We conclude that after melphalan chemotherapy, G-CSF may need to be given for only a short period to prevent chemotherapy-induced neutropenia, and that G-CSF induces a rapid rise in neutrophil levels even when started 8 days after melphalan administration.

Adult↗
PubMed1989

Evidence for a novel in vivo control mechanism of granulopoiesis: mature cell-related control of a regulatory growth factor.

As part of phase I/II clinical trials of granulocyte colony-stimulating factor (G-CSF), the pharmacokinetics was studied. To determine the optimal way of abrogating the neutropenia caused by melphalan, patients received G-CSF and melphalan on several schedules. The half-life (t 1/2) of elimination of G-CSF was in the range 1.3 to 4.2 hours and was prolonged at higher doses, suggesting that one clearance mechanism becomes saturated at doses greater than 10 micrograms/kg, When a continuous subcutaneous (SC) infusion was administered for five days, a rapid reduction in serum G-CSF levels occurred during the last two days of the infusion, indicating that an additional clearance mechanism was induced. When a continuous infusion of G-CSF was administered after melphalan, serum G-CSF levels remained constant for a longer period of time but did decrease during the second phase of a biphasic neutrophil response. In another clinical trial, G-CSF was administered after high-dose chemotherapy and autologous bone marrow transplantation (ABMT). In these patients, the G-CSF levels did not decrease while the patients were neutropenic. These results show that increased neutrophil levels are associated with increased clearance of G-CSF. This may be one of the negative feedback mechanisms involved in maintaining neutrophil homeostasis in normal and disease states.

Cell Differentiation↗
PubMed1988

Effects of bombesin antagonists on the growth of small cell lung cancer cells in vitro.

Small cell lung cancer (SCLC) produces several neuroendocrine peptides, including gastrin-releasing peptide (GRP), the mammalian equivalent of bombesin. There is some evidence to support the suggestion that GRP is an autocrine regulator of SCLC growth. Therefore, we have tested the effect of bombesin and two antagonists of bombesin on SCLC cell growth in a serum-free liquid tissue culture system. The antagonists used were analogues of substance P: spantide and (D-Arg1, D-Pro2, D-Trp7,9, Leu11) substance P. The cell lines used in this study all produced GRP-related peptides and one line had demonstrable GRP receptors. Exogenous bombesin did not cause any stimulation of growth in the liquid culture assay. The bombesin antagonists inhibited SCLC cell growth, but apparently not via the bombesin receptor. The bombesin used was biologically active because it stimulated the proliferation of Swiss 3T3 fibroblasts. The antagonists caused inhibition of this bombesin-induced proliferation, which was reversed by addition of excess bombesin. In addition, the antagonists and substance P alone stimulated proliferation of 3T3 cells, indicating that they may interact with another growth factor receptor on 3T3 cells. We conclude that growth of SCLC cells is not dependent on bombesin under all in vitro culture conditions because bombesin failed to stimulate growth in liquid cultures and the growth inhibition caused by bombesin antagonists was probably not mediated by the bombesin receptor.

Animals↗
PubMed1986

Immunologic response to aerosols of affinity-purified antigen in hypersensitivity pneumonitis.

On epidemiologic grounds, respirable particles from chilled-water air-conditioning systems in textile production plants have been implicated as a cause of hypersensitivity pneumonitis. We have purified the antigen from scum growing in this chilled water by antibody-affinity chromatography by use of IgG isolated from a pool of serum obtained from three workers with disease. Two patients with the disease, three coworkers without the disease, and two unexposed control subjects inhaled a dose of the purified antigen approximately equivalent to that amount calculated to be inhaled during an 8-hour work shift. Both workers with disease experienced fever, malaise, cough, and dyspnea 6 to 8 hours after the aerosol challenge. In these two patients the exposure evoked a transient decrease in circulating lymphocytes, predominantly T cells. Before challenge the patients' peripheral blood mononuclear cells demonstrated a blastogenic response to the antigen. The responding cells had disappeared from the circulation 24 hours after the challenge. Seventy-two hours after the challenge, mononuclear cells that were producing large amounts of specific IgG antibody appeared in the circulation. We conclude that the same antigen(s) that react with IgG antibody produced an acute episode of the disease, that specific antigen-recognition cells disappear from the peripheral blood after exposure to the antigen (presumably because they are attracted to the lung), and that antibody-forming cells appear in the peripheral blood approximately 2 days after a challenge. These antigen-specific reactions of circulating mononuclear cells may be specific for the disease, but studies on a larger number of cases are needed to be certain.

Aerosols↗
PubMed1985

Serological, biochemical, and functional identity of B cell-stimulatory factor 1 and B cell differentiation factor for IgG1.

By three criteria, we have demonstrated that B cell stimulatory factor (BSF-1) and B cell differentiation factor (BCDF-gamma) are the same lymphokine. Highly purified preparations of high performance liquid chromatography-purified or affinity-purified BSF-1 had BCDF-gamma activity but not BCDF-mu activity. A monoclonal anti-BSF-1 antibody coupled to Sepharose depleted both BSF-1 and BCDF-gamma activity but not BCDF-mu activity from two different T cell supernatants. Soluble monoclonal anti-BSF-1 blocked the BSF-1 and BCDF-gamma but not the BCDF-mu responses. These results suggest that BSF-1 acts on both resting and activated B cells to induce different effects.

Animals↗
PubMed1985

Small and large B cells respond differently to T cell-derived B cell growth and differentiation factors.

A major problem in B cell biology is the determination of the roles played by helper T (TH) cells vs cytokines in the activation, replication, and differentiation of B lymphocytes. There is general agreement that activated B cells in cycle can replicate and terminally differentiate when provided with appropriate T cell-derived lymphokines. There is considerable controversy, however, as to whether cytokines can induce resting G0 B cells to secrete IgM. Some reports claim that TH cells are required before cytokines can act. In contrast, other reports claim that some T cell-derived supernatants (SN) have the capacity to activate resting B cells to become immunoglobulin-secreting cells. In the present study, we have examined one such SN (S26.5) as well as the EL-4 and PK 7.1 SN for their capacity to activate resting G0 B cells and a population of less dense B cells containing activated cells. These two populations, separated by Percoll density centrifugation, were characterized for size, stage in the cell cycle, and cell surface phenotype. It was shown that the most dense population contained predominantly G0 B cells, whereas the less dense population contained a subset of cells in cycle. Our studies show that neither T cell SN nor, indeed, any combination of cytokines and anti-immunoglobulins caused a major increase in the number of cells secreting IgM in the population enriched in G0 cells. In contrast, the T cell SN caused marked increases in the generation of IgM secreting cells in the population that contained a large proportion of activated cells. Limiting dilution analysis confirmed that the number of responding cells in the dense cell population was substantially lower than the number of responding cells in the less dense population. The small number of precursors in the dense B cell population may be attributed to contamination of that population with cells that have undergone activation steps in vivo. The present results, therefore, add further evidence to an existing large body of evidence that TH cells are essential for the terminal differentiation of G0 resting B cells in response to thymus-dependent antigens.

Animals↗
PubMed1985

Activation of the gamma 1 gene by lipopolysaccharide and T cell-derived lymphokines containing a B cell differentiation factor for IgG1 (BCDF gamma).

By using both pulse labeling of nascent RNA chains and lactoperoxidase-catalyzed cell surface radioiodination, we examined both the de novo synthesis of mRNA for gamma-chains and the expression of membrane IgG (mIgG) on cells which had been stimulated with LPS plus a T cell supernatant (SN) containing a B cell differentiation factor for IgG1 (BCDF gamma). Our results show that neither nascent mRNA for gamma 1 chains nor mIgG1 can be detected in B lymphocytes until they have been stimulated by both LPS and BCDF gamma-containing T cell SN, and suggest that cell surface expression and secretion of IgG1 are coordinately controlled.

Animals↗
PubMed1984

Clonal analysis of B cells induced to secrete IgG by T cell-derived lymphokine(s).

To gain insight into how T cell-derived lymphokines induce the secretion of IgG in activated B cells, we performed a limiting dilution analysis, using murine splenic B cells incubated with lipopolysaccharide (LPS) and a T cell-derived B cell differentiating factor for IgG (BCDF gamma)-containing supernatant (SN). The results of this analysis indicate that such a SN induces a marked increase in the precursor frequency of IgG1-secreting cells and a modest increase in clone size. The precursors lack surface IgG and are committed to the differentiation pathway for IgG1 secretion after LPS activation, but before the addition of BCDF gamma-containing SN. The majority of IgG1-secreting clones arise independently from precursors of cells that secrete IgG3. Taken together, these results indicate that BCDF gamma directs differentiation of activated B cells to IgG1 secretion.

Animals↗
PubMed1980

Anti-carbohydrate activity of T cell-reactive chicken anti-mouse immunoglobulin antibodies.

The specificity of chicken anti-mouse immunoglobulin F(ab')2 antibodies, which bind readily to T cells and have been claimed to detect immunoglobulin on T cells, was analyzed by indirect immunofluorescence. It ws found that only a minor proportion of the total antibody bound to T cells whereas the major fraction bound only to B cells. The T cell-reactive antibody cross-reacted with bovine IgG and therefore could be purified on this basis by affinity chromatography. T cell staining was inhibitable with nonimmunoglobulin glycoproteins as well as immunoglobulin, in contrast to staining with the B cell-specific antibody fraction, which was only inhibited by immunoglobulin. This suggested that the T cell staining was caused by anti-carbohydrate antibody. Inhibition of T cell staining was abolished by periodate oxidation of the inhibitors but not by proteolytic digestion. In addition, the antigenic determinant on the cell surface was not destroyed by autoclaving. Finally, antibody was absorbed on a mucin-Sepharose column and anti-T cell activity was found in the bound but not the unbound fraction. These results strongly suggest that the only anti-T cell activity in the chicken antibody is anti-carbohydrate antibody.

Absorption↗
PubMed1979

In vitro model for natural tolerance to self-antigens. Inhibition of the development of surface-immunoglobulin-negative lymphocytes into T-dependent responsive B cells by antigen.

Neonatal and adult splenic cell suspensions were labeled with fluorescein isothiocynate-anti-Ig and fractionated into surface-immunoglobulin- (s-Ig) positive and s-Ig-negative subpopulations by the fluorescence-activated cell sorter. The subpopulations were then tested by splenic focus assay for both frequency and tolerance susceptibility of clonable 2,4,-dinitrophenol (DNP) precursors. It was shown that both adult, and neonatal, s-Ig-negative subsets contained clonable DNP-specific B-cell precursors. However, because these precursors result in fewer clones secreting IgG, they appeared to be less mature than the s-Ig-positive precursors. In the absence of helper T cells, it was found that exposure of s-Ig-negative lymphocytes to tolerogen during the process in which they were acquiring surface receptors resulted in nearly total abrogation of potential DNP clones. This finding provides compelling evidence for clonal abortion.

Animals↗
PubMed1979

Maturation of B lymphocytes. II. Sequential appearance of increasing IgM and IgD in the adult bone marrow.

The relationship between surface IgM (sIgM) and surface IgD (sIgD) was examined on small lymphocytes in the adult murine bone marrow or prepubertal spleen. Cells were sorted on the basis of different sIgM levels by a fluorescence-activated cell sorter (FACS) and relabeled for sIgD or total sIg by a sandwich technique using 125I-labeled protein A and radioautography. For detecting sIgD, an anti-delta allotype reagent was used in congenic mice. Cells lacking sIgM in the bone marrow or spleen were also found to be sIgD-; thus, sIgD appeared only in the presence of sIgM. Weak sIgM-bearing cells in the bone marrow also had no sIgD indicating that sIgD appeared only after the acquisition of a significant level of sIgM. Subsequently, the incidence of sIgD+ cells increased in fractions showing increasing sIgM levels indicating the acquisition of new sIgD by "sIgM only" cells with increasing maturation levels in the bone marrow. In marrow lymphoid cells expressing both Ig isotypes, sIgM and sIgD levels increased in parallel, possibly with increasing maturation level. In the spleen, the incidence of sIgD+ cells among various cell fractions showing different sIgM levels was found constant. However, spleen cells bearing both receptors, showed a small increase in the sIgD level with increasing sIgM level.

Aging↗