Interleukin 4 (IL 4)-induced IgE production by peripheral blood lymphocytes and tonsil cells from normal donors was enhanced in a dose-dependent fashion by IL 5. IL 5 tested alone was not effective. The synergistic effects of IL 5 were most pronounced at suboptimal IL 4 concentrations, whereas at saturating IL 4 concentrations (200-300 U/ml), IL 5 had no effect. Interferon-gamma (IFN-gamma) and F(ab')2 fragments of monoclonal antibody 25 directed against the CD23 antigen, that blocked IL 4-induced IgE synthesis, also inhibited the production of IgE in the presence of combinations of IL 4 and IL 5, indicating that IL 5 potentiates the activation pathway through which IL 4 induces IgE production. In contrast, IL 4 (50 U/ml) blocked IL 5-induced IgA synthesis. IL 5 was ineffective in inducing the release of soluble CD23 (sCD23), but in the presence of IL 4 an enhanced release of sCD23 was observed, provided IL 4 was present at suboptimal concentrations. IFN-gamma completely blocked sCD23 release induced by IL 4 and IL 5. These results demonstrate that there is a strong quantitative correlation between sCD23 release and induction of IgE synthesis. sCD23 fraction-correlation between sCD23 release and induction of IgE synthesis. sCD23 fractionated from the Epstein-Barr virus-transformed B cell line RPMI 8866 was ineffective in inducing IgE production. However, sCD23 acted synergistically with suboptimal concentrations of IL 4. sCD23 did not modulate the IgE response at saturating concentrations of IL 4. Collectively, these data indicate that sCD23 plays an important regulatory role in the modulation of IL 4-induced IgE synthesis mediated by IFN-gamma and IL 5.
The growth-promoting activities of interleukin-6 (IL-6) in combination with different factors were assessed in bone marrow (BM) cultures prepared from normal mice and from mice treated with 5-fluorouracil (5- FU). Effects on hematopoietic colony formation with respect to number, size, and cellular composition were evaluated. In agreement with previous reports, IL-6 acts synergistically with IL-3 to stimulate increased numbers of granulocyte/macrophage (GM) and multilineage colonies in day-2 and day-4 post-5-FU BM cultures. Furthermore, day 4 but not day 2 post-5-FU BM showed enhanced GM colony formation when stimulated with IL-6 plus interleukin-4 (IL-4) or granulocyte colony- stimulating factor (G-CSF). In contrast, IL-6 did not increase the number of colonies supported by M-CSF or GM-CSF. Nevertheless IL-6 interacted with all factors, including M-CSF and GM-CSF, to stimulate an increase in colony size. Many of these myeloid colonies attained a diameter of greater than or equal to 0.5 mm, suggesting they derive from high proliferative potential cells (HPP-CFC). The response of normal and day-8 post-5-FU BM containing high numbers of more mature progenitors was also assessed. We found IL-6 enhanced colony formation by lineage-restricted megakaryocytic and erythroid progenitors in the presence of IL-3 and IL-4 plus erythropoietin (Epo), respectively. The sum of these results shows that IL-6 interacts with a variety of factors to regulate the growth of progenitor cells at different stages of lineage commitment and maturation.
authors request that the following error be noted on p. 1272, in the second paragraph from the bottom of the right-hand column. The bacteriophage T4 gene identified by Belfort and colleagues (ref. 53) as containing an intron encodes thymidylate synthase, not thymidine kinase. CorrectionsProc. Nail. Acad. Sci. USA Vol. 83, pp. 1242-1245, March 1986 BiochemistryThe primary structure of rat parathymosin ABSTRACTParathymosin has been isolated from rat thymus and from rat liver. Its primary structure is reported 10 as follows:AcSer-Lys-Ser-Glu-Val -Glu-Ala-Ala-Ala-Glu -20 Leu-Ser-Ala-Lys-Asp-Leu-Lys-Glu-Lys-Lys -Asp-Lys- Glu-Glu-Lys-Ala-Gly-Arg-Lys-Glu-Arg-Lys-Lys-Glu- Val-Glu-Glu-Glu -Glu-Asn-Gly-Ala-Glu-Glu-Glu-Glu-Gluso 80Glu -Thr-Ala-Glu-(Gly3,Asx7,Glx14)-Glu-Gly-Pro -Val-Arg- 90Lys-Arg-Thr-Ala-Glu-Glu-Glu-Asp -Glu-Ala-Asp-Pro-Lys- 100Arg-Gln-Lys-Thr-Glu Asn-Gly-Ala-Ser-AlaOH. The blockmg group at the NH2 terminus was identified by mass spectrometry as acetyl. Regions homologous to amino acid sequences in prothymosin a were found to be located between residues 14-20, 23-25, 33-39, 41-43, and 83-87 of parathymosin.Parathymosin was first isolated from rat thymus (1) as a by-product of the procedure used for the isolation of prothymosin a. It was named parathymosin because of its structural similarity to prothymosin a, the putative precursor of thymosin a1 (2, 3 In the present paper, we report a simplified procedure for the isolation of both peptides from rat thymus and the nearly complete amino acid sequence ofparathymosin. A procedure for the isolation of parathymosin from rat liver, a richer source for this peptide, is also described. MATERIALS AND METHODSMaterials. Rat tissues were collected immediately after sacrifice of the animals by decapitation, frozen in liquid N2, and stored at -70'C. Other materials were from sources identified earlier (1, 3, 4).Methods. Chromatography on Sephacryl S-200 was carried out as described (1). For the HPLC, a Waters Associates system with an Altex Ultrasphere ODS C18 column was used.Protein and peptide analyses were carried out fluorometrically following alkaline hydrolysis and reaction with fluorescamine (7). Automated sequence analysis was as described (3). The quantitative radioimmunoassay for prothymosin a was as described by Haritos and Horecker (4 9.0 with K2CO3. After 4 hr at 50°C, the solution was acidified with 26 ul of concentrated HCOOH, diluted with 10 ml of buffer A (1 M HCOOH/0.2 M pyridine, pH 2.8) and pumped through a Sep-Pak C18 cartridge. After the cartridge was washed with 10 ml of buffer A, the peptides were eluted with 3 ml of 40% acetonitrile in buffer A, and the eluate was lyophilized.Digestion with Staphylococcus aureus V8 protease was in 25 ,ul of 0.1 M NH4HCO3 containing 50 ,ug of peptide, 2 mM EDTA, and 1.67 ,ug of protease. After 13 hr at 37°C, the solution was lyophilized.For the isolation of peptides in the proteinase digests and after treatment with H2NOH, the lyophilized solutions were dissolved in buffer A and separated by HPLC using the OD...
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