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Interleukin la (IL-la), IL-2, IL-4, IL-6, gamma interferon (IFN-y), tumor necrosis factor alpha (TNF-c), and granulocyte macrophage colony-stimulating factor (GM-CSF) were tested for their abilities to alter the growth of Brucella abortus in BALB/c J774A.1 murine macrophages. IL-la, IL-4, IL-6, tumor necrosis factor alpha, and granulocyte macrophage-colony-stimulating factor had no consistent or significant effect on the growth of the avirulent B. abortus strain 19. In contrast, the addition of either IFN-y or IL-2 at 100 U/ml to the macrophage cultures resulted in a significant reduction in the number of intracellular bacteria that was not attributable to decreased infection rates. With IL-2, the reduction was most often apparent only during the first 24 h after infection, while inhibition with IFN-y was apparent throughout the culture period of 48 h. The addition of either IL-2 or IFN-y to macrophage cultures also resulted in reduced intracellular CFU of the virulent B. abortus strain 2308 and the attenuated rough mutant B. abortus strain RB51. Inhibition of intracellular growth was not augmented by combinations of cytokines. Additional studies with IFN-'y and IL-2 indicated that they could mediate the inhibition of intracellular growth of B. abortus in resident and thioglycolate broth-induced BALB/c peritoneal macrophages and in splenic macrophages. IFN-y also inhibited bacterial growth when added after infection of the macrophages, although the magnitude of the antibrucellae effects was less than that when it was added before infection. Furthermore, the maximal inhibitory effect was sustained only when IFN-y remained in the cultures after infection of the macrophages.

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Channel gating of the cystic fibrosis transmembrane conductance regulator (CFTR) is activated in response to cAMP stimulation. In addition, CFTR activation may also involve rapid insertion of a subapical pool of CFTR into the plasma membrane (PM). However, this issue has been controversial, in part because of the difficulty in distinguishing cell surface vs. intracellular CFTR. Recently, a fully functional, epitope-tagged form of CFTR (M2-901/CFTR) that can be detected immunologically in nonpermeabilized cells was characterized (Howard M, Duvall MD, Devor DC, Dong J-Y, Henze K, and Frizzell RA. Am J Physiol Cell Physiol 269: C1565-C1576, 1995; and Schultz BD, Takahashi A, Liu C, Frizzell RA, and Howard M. Am J Physiol Cell Physiol 273: C2080-C2089, 1997). We have developed replication-defective recombinant adenoviruses that express M2-901/CFTR and used them to probe cell surface CFTR in forskolin (FSK)-stimulated polarized Madin-Darby canine kidney (MDCK) cells. Virally expressed M2-901/CFTR was functional and was readily detected on the apical surface of FSK-stimulated polarized MDCK cells. Interestingly, at low multiplicity of infection, we observed FSK-stimulated insertion of M2901/CFTR into the apical PM, whereas at higher M2-901/CFTR expression levels, no increase in surface expression was detected using indirect immunofluorescence. Immunoelectron microscopy of unstimulated and FSK-stimulated cells confirmed the M2-901/CFTR redistribution to the PM upon FSK stimulation and demonstrates that the apically inserted M2-901/CFTR originates from a population of subapical vesicles. Our observations may reconcile previous conflicting reports regarding the effect of cAMP stimulation on CFTR trafficking.