ABSTRACT
Chemokines are essential mediators of normal leukocyte trafficking as well as of leukocyte recruitment during inflammation. We describe here a novel non-ELR CXC chemokine identified through sequence analysis of cDNAs derived from cytokine-activated primary human astrocytes. This novel chemokine, referred to as I-TAC (interferon-inducible T cell alpha chemoattractant), is regulated by interferon (IFN) and has potent chemoattractant activity for interleukin (IL)-2-activated T cells, but not for freshly isolated unstimulated T cells, neutrophils, or monocytes. I-TAC interacts selectively with CXCR3, which is the receptor for two other IFN-inducible chemokines, the IFN-gamma-inducible 10-kD protein (IP-10) and IFN-gamma- induced human monokine (HuMig), but with a significantly higher affinity. In addition, higher potency and efficacy of I-TAC over IP-10 and HuMig is demonstrated by transient mobilization of intracellular calcium as well as chemotactic migration in both activated T cells and transfected cell lines expressing CXCR3. Stimulation of astrocytes with IFN-gamma and IL-1 together results in an approximately 400,000-fold increase in I-TAC mRNA expression, whereas stimulating monocytes with either of the cytokines alone or in combination results in only a 100-fold increase in the level of I-TAC transcript. Moderate expression is also observed in pancreas, lung, thymus, and spleen. The high level of expression in IFN- and IL-1-stimulated astrocytes suggests that I-TAC could be a major chemoattractant for effector T cells involved in the pathophysiology of neuroinflammatory disorders, although I-TAC may also play a role in the migration of activated T cells during IFN-dominated immune responses.
Subject(s)
Chemokines, CXC/metabolism , Lymphocyte Activation , Receptors, Chemokine/metabolism , T-Lymphocytes/immunology , Amino Acid Sequence , Astrocytes , Base Sequence , Calcium/metabolism , Chemokine CXCL11 , Chemokines, CXC/genetics , Chemotaxis, Leukocyte , Chromosomes, Human, Pair 4 , Cloning, Molecular , DNA, Complementary/genetics , Desensitization, Immunologic , Humans , Interferon-gamma/pharmacology , Molecular Sequence Data , Protein Binding , RNA, Messenger/biosynthesis , Receptors, CXCR3 , Sequence Analysis, DNA , Sequence Homology, Amino Acid , T-Lymphocytes/drug effectsABSTRACT
A simple method is described for labeling carbapenems with [14C]dimethyl sulfate. Reverse-phase high-performance liquid chromatography of the reaction was used to purify the product. Carbapenems with 2-substituents containing pyrid-3-yl and -4-yl moieties could be labeled by this method, but those containing a pyrid-2-yl group could not. Nonreversible binding of these labeled carbapenems to human serum albumin was investigated. Pyridinium-3-yl compounds displayed low binding rates (0.028 to 0.044%/h), whereas three of four pyridinium-4-yl compounds bound much faster (0.38 to 0.62%/h). It is postulated that these differences are related to the ability of the compound to stabilize a deprotonated form transiently.