Showing papers by "National Jewish Health published in 1983"

T cell-derived B cell growth and differentiation factors. Dichotomy between the responsiveness of B cells from adult and neonatal mice.

Abstract: In these studies we have determined the molecular weights of B cell growth factor (BCGF) (less than 20,000), and B cell differentiation factors (BCDF) that induce immunoglobulin M (IgM) secretion (BCDF mu) (30-60,000) and IgG secretion (BCDF gamma) (less than 20,000). Thus, the molecular weight of BCDF mu is distinct from that of BCGF and BCDF gamma; BCGF and BCDF gamma cannot be distinguished. In addition, BCGF, BCDF mu, and BCDF gamma are distinguishable by their presence or absence in different supernatants from a panel of mitogen-induced T cell clones. These results suggest that the three lymphokines are different. This conclusion is supported by their differential biological effect on B cells from adult and neonatal mice. Thus, treatment with anti-Ig induces B cells from adult mice to proliferate and this proliferation is sustained by BCGF. In contrast, even in the presence of BCGF, anti-Ig does not induce B cells from neonatal mice to proliferate. However, BCDF mu and BCDF gamma induce IgM and IgG secretion in B cells, respectively, from both adult and neonatal mice. Thus, mature B cells can both clonally expand and differentiate in response to anti-Ig, BCGF, and BCDF, whereas immature B cells can only differentiate. The poor response of neonatal B cells to anti-Ig and BCGF may partially explain the relative immunoincompetence of immature B cells.

Coordinate production by a T cell hybridoma of gamma interferon and three other lymphokine activities: multiple activities of a single lymphokine?

Abstract: The T cell hybridoma FS7-20, produced by the fusion of normal B10.BR T cells to the AKR thymoma BW5147, was found when stimulated with concanavalin A (Con A) to produce the lymphokines: interleukin 2 (IL 2), interferon-gamma (IFN gamma), macrophage-activating factor (MAF), Ia induction factor IaIF), and the B cell helper factor interleukin X (IL X). The clones and subclones of FS7-20 varied dramatically in their ability to produce these lymphokines, presumably because of karyotypic variations. The ability to produce IL 2 segregated independently from the ability to produce the four other lymphokine activities; however, production of the latter activities showed a strong correlation. This coordinate production of IFN gamma, MAF, IaIF, and IL X was also observed with a cloned normal cytotoxic T cell line, cr15. These results suggest either that IFN gamma, MAF, IaIF, and IL X are all manifestations of a single molecular species or that, although these activities are different structurally, their production is controlled by a common genetic mechanism. In support of the first possibility, the IFN gamma, MAF, IaIF, and IL X activity produced by FS7-20 were all found to be equally sensitive to inactivation at pH 2. These results illustrate the usefulness of using T cell hybridomas for the study of lymphokines.

Identification and sequence of the initiation slte for rat 45S ribosomal RNA synthesis

Abstract: The transcription initiation site for rat 45S precursor ribosomal RNA synthesis was determined by nuclease protection mapping with two single-strand endonucleases. S1 and mung bean, and one single-strand exonuclease, ExoVII. These experiments were performed with end-labeled ribosomal DNA from double-stranded pBR322 recombinants and from single-stranded M13 recombinants. Results from experiments using both kinds of DNA and all three enzymes showed that the 5' end of 45S RNA mapped to a unique site 125 bases upstream from the Hind III site in the ribosomal DNA gene. The DNA surrounding this site (designated +1) was sequenced from -281 to +641. The entire sequence of this region shows extensive homology to the comparable region of mouse. This includes three stretches of T residues in the non-coding strand between +300 and +630. Two sets of direct repeats adjacent to these T-rich regions are observed. Comparison of the mouse and human ribosomal DNA transcription initiation sites with the rat sequence reported in this paper demonstrates a conserved sequence at +2 to +16, CTGACACGCTGTCCT. This suggests that this region may be important for the initiation of transcription on mammalian ribosomal DNAs.