Publications

The carboxyl terminus of the G protein alpha subunit is a key determinant of the fidelity of receptor activation. We have previously shown that the Gq alpha subunit (alpha q) can be made to respond to alpha i-coupled receptors by replacing its carboxyl terminus with the corresponding alpha i2, alpha o, alpha z residues. We now extend these findings in three ways: 1) carboxyl-terminal mutations of alpha q/alpha i chimeras show that the critical amino acids are in the -3 and -4 positions, 2) exchange of carboxyl termini between alpha q and alpha z allows activation by receptors appropriate to the carboxyl-terminal residues, and 3) we identify receptors that either do or do not activate the expected carboxyl-terminal chimeras (alpha q/alpha i, alpha q/alpha s, alpha s/alpha q). Replacement of the five carboxyl-terminal amino acids of alpha q with the alpha s sequence permitted an alpha s-coupled receptor (the V2 vasopressin receptor but not the beta 2-adrenergic receptor) to stimulate phospholipase C. Replacement of the five carboxyl-terminal amino acids of alpha z with residues of alpha q permitted certain alpha q-coupled receptors (bombesin and V1a vasopressin receptors but not the oxytocin receptor) to stimulate adenylyl cyclase. Thus, the relative importance of the G alpha carboxyl terminus in permitting coupling to a new receptor depends on the receptor with which it is paired. These studies refine our understanding and provide new tools with which to study the fidelity of receptor/G alpha activation.

A number of investigations have established the critical role of interleukin 4 (IL-4) in mediating the development of T helper (Th)2 effector cells in vitro and in vivo. Despite intensive study, the origin of the IL-4 required for Th2 priming and differentiation remains unclear. Natural killer (NK)1.1+ alpha/beta T cell receptor+ T(NT) cells, a unique lineage of cells capable of producing large amounts of IL-4 after activation in vivo, are important candidates for directing Th2 priming. These cells are selected by the nonpolymorphic major histocompatibility complex (MHC) class I molecule, CD1, and are deficient in beta 2-microglobulin (beta 2m)-null mice. We used beta 2m-deficient mice on both BALB/c and C57BL/6 backgrounds to examine their capacity to mount Th2 immune responses after challenge with a number of well-characterized antigens administered by a variety of routes. As assessed by immunization with protein antigen, infection with Leishmania major, embolization with eggs of Schistosoma mansoni, intestinal infection with Nippostrongylus brasiliensis, or induction of airway hyperreactivity to aerosolized antigen, beta 2m-deficient mice developed functional type 2 immune responses that were not substantially different than those in wild-type mice. Production of IL-4 and the generation of immunoglobulin E (IgE) and eosinophil responses were preserved as assessed by a variety of assays. Collectively, these results present a comprehensive analysis of type 2 immune responses in beta 2m-deficient mice, and indicate that beta 2m-dependent NT cells are not required for Th2 development in vivo.

The aim of this study was to determine the dose-response relationship between cigarette smoke exposure and pulmonary cell and cytokine concentrations in bronchoalveolar lavage (BAL). BAL cells and BAL supernatant concentrations of tumour necrosis factor-alpha (TNF alpha), interleukin (IL)-1 beta, IL-6, IL-8, and monocyte chemoattractant protein (MCP)-1 from 14 healthy smokers and 16 healthy nonsmokers were quantified. Statistically greater concentrations of neutrophils, macrophages, IL-1 beta, IL-6, IL-8 and MCP-1 were observed among smokers compared with nonsmokers (p < or = 0.0007 in all cases). Cigarette smoking, categorized ordinally as: less than one pack, one pack, or greater than one pack per day, was predictive of BAL macrophages (p < 0.0001), neutrophils (p = 0.015), IL-1 beta (p < 0.001) and IL-8 (p = 0.02). We conclude that concentrations of macrophages, neutrophils, IL-1 beta and IL-8 are elevated in the pulmonary microenvironment of smokers in a cigarette dose-dependent manner. Based on the present findings, we would caution against simple analyses that treat current smokers as a homogeneous group and which do not account for smoking intensity.