Biomedical subjects

L Hibbert

Publications and source records attributed to L Hibbert.

4 recordsLinked to original sources

PubMed1999

Human type I interferons differ greatly in their effects on the proliferation of primary B cells.

We examined the effects of eight subtypes of human interferon-alpha (IFN-alpha) and human IFN-beta on primary human B cells. In costimulation with antibodies to IgM (but not to CD40), some of these induced the cells to proliferate (but not to differentiate). Individual IFN differed greatly in their relative proliferative effects. IFN-alpha8 at 0.1-0.5 ng/ml induced proliferation, whereas most other subtypes were active only at concentrations >5 ng/ml, and IFN-alpha1 was inactive. These marked differences were not due to a selective overall increase in B cell response only to some IFN subtypes, as all those tested similarly induced the IFN-inducible genes 6-16 and HLA class I. Our results show that human B cells must respond to type I IFN via two distinct pathways. One is specific for IFN-alpha8 but can be activated by other IFN at relatively high concentrations. The other responds to them all and causes activation of IFN-inducible genes.

B-Lymphocytes↗

PubMed1997

X-SCID B cell responses to interleukin-4 and interleukin-13 are mediated by a receptor complex that includes the interleukin-4 receptor alpha chain (p140) but not the gamma c chain.

This study investigates the effect of interleukin (IL)-4 mutant proteins and a monoclonal antibody to the IL-4 receptor alpha chain on IL-4 and IL-13 response by B cells from X-linked severe combined immunodeficiency (X-SCID) patients in which the common gamma chain (gamma c chain) gene mutations have been fully characterized and no gamma c chain expression was detected. In this gamma c chain gene knockout model, it was confirmed that the gamma c chain is essential for B cell responses to IL-2 but not for IL-4 or IL-13. Dose-response curves for X-SCID and normal B cell responses to IL-4 were indistinguishable, showing that the loss of the gamma c chain did not diminish the sensitivity of B cells to IL-4. The mutant protein IL-4(Y124D) and an antibody to the IL-4R alpha chain both inhibited responses of X-SCID B cells to IL-4 and IL-13, showing that X-SCID B cell responses to these cytokines are mediated by a receptor complex that includes the IL-4R alpha chain but not the gamma c chain. Another mutant protein, IL-4(R88D), which has greatly reduced affinity for IL-4R alpha, was found to inhibit responses by normal B cells to IL-4 but not to IL-13. IL-4(R88D), did not, however, inhibit X-SCID B cell responses to IL-4. This result is consistent with IL-4(R88D) inhibition of responses mediated by receptor complexes that include the gamma c chain. We propose that X-SCID B cells responses to IL-4 are mediated by an IL-13 receptor complex comprised of the IL-4R alpha chain associated with the recently cloned IL-13R binding protein. This model has major implications for understanding normal B cell responses to IL-4.

Animals↗

PubMed1996

IL-4 and IL-13 receptors: are they one and the same?

Interleukin 4 (IL-4) and IL-13 share several biological properties, suggesting that they also share a common receptor or receptor component. Indeed, as discussed here by Robin Callard and colleagues, the IL-13 receptor appears to be a functional receptor for IL-4.

Animals↗

PubMed1994

Engineering the maltose binding protein for reagentless fluorescence sensing.

This paper describes a mutant of the maltose binding protein (MBP) in which the serine residue at position 337 is replaced by a cysteine residue using site-directed mutagenesis. The mutant MBP has an approximately 2-fold lower affinity for maltose, and the cysteine residue can be modified with 4-[N-(2-(iodoacetoxy)ethyl)-N-methylamino]-7-nitrobenz-2-oxa-1,3-diazole (IANBD) and 6-acryloyl-2-(dimethylamino)-naphthalene (acrylodan). This combined genetic and chemical modification places the fluorophores close to the maltose binding site such that when the ligand is added the fluorescence intensity of the labels increases by 60-180% over that of the ligand-free form. This change is consistent with the fluorophores being buried when the conformation of the protein changes with maltose binding. Titration of the labeled mutant proteins yields dissociation constants for maltose of 62 +/- 0.2 and 0.8 +/- 0.01 microM respectively for the IANBD and acrylodan modifications. The application of this strategy of combined genetic and chemical modification to the development of reagentless fluorescence sensing is discussed.

2-Naphthylamine↗