Enhanced delayed-type hypersensitivity and diminished immediate-type hypersensitivity in mice lacking the inducible VPAC(2) receptor for vasoactive intestinal peptide.

Vasoactive intestinal peptide (VIP) and its G protein-coupled receptors, VPAC(1)R and VPAC(2)R, are prominent in the immune system and regulate many aspects of T cell-dependent immunity. In mouse T cells, VPAC(1)R is expressed constitutively, whereas VPAC(2)R is induced by immune stimuli. VPAC(2)R-null (VPAC(2)R(-/-)) mice on a C57BL/6 background are shown here to have normal basic immune characteristics, including serum Ig concentrations, blood levels of all leukocytes, and spleen number of total T cells (CD3(+)) and T cells bearing CD4, CD8, and CD28. Hapten-evoked cutaneous delayed-type hypersensitivity (DTH) was significantly enhanced in VPAC(2)R-null mice compared with age- and sex-matched wild-type mice. In contrast, generation of IgE anti-hapten antibodies and active cutaneous anaphylaxis were > or =70% lower in VPAC(2)R-null mice than in wild-type controls. Cytokine production by splenic CD4(+) T cells, stimulated with adherent anti-CD3 plus anti-CD28 antibodies, revealed higher levels of IL-2 (mean = 3-fold) and IFN-gamma (mean = 3-fold), and lower levels of IL-4 (mean = one-fifth) in VPAC(2)R-null mice than wild-type controls. Loss of VIP-VPAC(2)R maintenance of the normal ratio of Th2/Th1 cytokines thus leads to a state of enhanced DTH and depressed immediate-type hypersensitivity, which may alter both host defense and susceptibility to immune-mediated diseases.

Allergic diathesis in transgenic mice with constitutive T cell expression of inducible vasoactive intestinal peptide receptor.

Vasoactive intestinal peptide (VIP) and its G-protein-coupled receptors (VPAC1 and VPAC2 Rs) are prominent in the immune system. In T cells, VPAC1 R is expressed constitutively whereas VPAC2 R is induced only after stimulation of the T cell receptor (TCR) or exposure to some cytokines. VPAC1 R and VPAC2 R also transduce different effects of VIP on T cells. Constitutive expression of VPAC2 R selectively in CD4+ T cells (helper-inducer Th cells) of transgenic (TG) C57BL/6 mice directed by the lck tyrosine kinase promoter is now shown to evoke production of more Th2-type interleukins 4 and 5, and less Th1-type interferon gamma after TCR activation. VPAC2 R TG mice consequently have significant elevations of blood IgE, IgG1, and eosinophils. VPAC2 R TG mice also show increased IgE antibody responses, which mediate heightened cutaneous allergic reactions, and have depressed delayed-type hypersensitivity. VIP enhancement of the ratio of Th2 cell to Th1 cell cytokines thus evokes an allergic state in normally nonallergic mice, which suggests the possibility of neuropeptide contributions to immune phenotypic alterations in human hypersensitivity diseases.

Altered expression and functional profile of lysophosphatidic acid receptors in mitogen-activated human blood T lymphocytes.

Lysophosphatidic acid (LPA) from platelets and mononuclear phagocytes regulates T cell functions through endothelial differentiation gene-encoded G protein-coupled receptors (Edg Rs). Human blood unactivated CD4+ T cells express predominant ly Edg-4 LPA R over marginal levels of Edg-2 LPA R, as assessed by semiquantitative PCR and Western blots. After mitogen activation, the CD4+ T cells express Ed g-2 Rs at approximately one half the level of Edg-4 Rs. Secretion of IL-2 by unactivated Edg-4 R-predominant CD4+ T cells incubated with anti-CD3 plus anti-CD28 antibodies was suppressed significantly and by up to 60% by 10-10 M to 10-6 M LPA, whereas secretion of IL-2 by mitogen-activated Edg-2 R and Edg-4 R codominant CD4+ T cells was enhanced by up to twofold by the same concentrations of LPA. The possibility that the two Edg Rs transduce different LPA signals to CD4+ T cells was supported by findings that IL-2 secretion was inhibited by mouse anti-Edg-4 R monoclonal antibody, but enhanced by mouse anti-Edg-2 R monoclonal antibody. The separate effects of each LPA R were studied in Jurkat T cell transfectants expressing principally human Edg-2 Rs (Jurkat-T-2) or Edg-4 Rs (Jurkat-T-4) and stimulated with anti-CD3 plus phorbol myristate acetate. LPA and anti-Edg-4 R antibody suppressed IL-2 secretion by stimulated Jurkat-T-4 cells, whereas LPA and anti-Edg-2 R antibody enhanced IL-2 secretion by stimulated Jurkat-T-2 cells. Activation-induced alterations in the relative levels of Edg-2 and -4 Rs on CD4+ T cells thus reverse the effects of LPA on T cell receptor-stimulated generation of IL-2.

The interaction of meaning and sound in spoken word recognition.

Models of spoken word recognition vary in the ways in which they capture the relationship between speech input and meaning. Modular accounts prohibit a word's meaning from affecting the computation of its form-based representation, whereas interactive models allow activation at the semantic level to affect phonological processing. We tested these competing hypotheses by manipulating word familiarity and imageability, using lexical decision and repetition tasks. Responses to high-imageability words were significantly faster than those to low-imageability words. Repetition latencies were also analyzed as a function of cohort variables, revealing a significant imageability effect only for words that were members of large cohorts, suggesting that when the mapping from phonology to semantics is difficult, semantic information can help the discrimination process. Thus, these data support interactive models of spoken word recognition.

Cutting edge: differential constitutive expression of functional receptors for lysophosphatidic acid by human blood lymphocytes.

Lysophosphatidic acid (LPA) and sphingosine 1-phosphate (S1P) from platelets and macrophages mediate T cell functions. Endothelial differentiation gene-encoded G protein-coupled receptors (Edg Rs) are specific for S1P (Edg-1, -3, -5, and -8 Rs) and LPA (Edg-2, -4, and -7 Rs). Human T cell tumors express many Edg Rs for both LPA and S1P. In contrast, human blood CD4+ T cells express predominantly Edg-4, and CD8+ T cells show only traces of Edg-2 and -5, by quantification of mRNA and Edg R Ags. LPA at 10-10-10-6 M suppressed significantly the secretion of IL-2 from anti-CD3 plus anti-CD28 Ab-challenged CD4+ T cells, but not CD8+ T cells. Monoclonal anti-Edg-4 R Ab, like LPA, suppressed stimulated IL-2 secretion from CD4+ T cells, but not CD8+ T cells. Constitutive expression of Edg-4 by CD4+, but not CD8+, human T cells accounts for differential functional responsiveness of the T cell subsets to LPA.

Four human ras homologs differ in their abilities to activate Raf-1, induce transformation, and stimulate cell motility.

Human cells contain four homologous Ras proteins, but it is unknown whether each of these Ras proteins participates in distinct signal transduction cascades or has different biological functions. To directly address these issues, we assessed the relative ability of constitutively active (G12V) versions of each of the four Ras homologs to activate the effector protein Raf-1 in vivo. In addition, we compared their relative abilities to induce transformed foci, enable anchorage-independent growth, and stimulate cell migration. We found a distinct hierarchy between the four Ras homologs in each of the parameters studied. The hierarchies were as follows: for Raf-1 activation, Ki-Ras 4B > Ki-Ras 4A >>> N-Ras > Ha-Ras; for focus formation, Ha-Ras >/= Ki-Ras 4A >>> N-Ras = Ki-Ras 4B; for anchorage-independent growth, Ki-Ras 4A >/= N-Ras >>> Ki-Ras 4B = Ha-Ras = no growth; and for cell migration, Ki-Ras 4B >>> Ha-Ras > N-Ras = Ki-Ras 4A = no migration. Our results indicate that the four Ras homologs significantly differ in their abilities to activate Raf-1 and induce distinctly different biological responses. These studies, in conjunction with our previous report that demonstrated that the Ras homologs can be differentially activated by upstream guanine nucleotide exchange factors (Jones, M. K., and Jackson, J. H. (1998) J. Biol. Chem. 273, 1782-1787), indicate that each of the four Ras proteins may qualitatively or quantitatively participate in distinct signaling cascades and have significantly different biological roles in vivo. Importantly, these studies also suggest for the first time that the distinct and likely cooperative biological functions of the Ki-ras-encoded Ki-Ras 4A and Ki-Ras 4B proteins may help explain why constitutively activating mutations of Ki-ras, but not N-ras or Ha-ras, are frequently detected in human carcinomas.

Neutrophil Fc gamma and complement receptors involved in binding soluble IgG immune complexes and in specific granule release induced by soluble IgG immune complexes.

We examined the effect of soluble IgG immune complex (IC) characteristics on the binding of IC to human neutrophils and IC-induced specific granule release of neutrophils via Fc gamma receptors (CD16 and CD32) and complement receptors (CR1 and CR3). A set of soluble IgG IC varying in size, IgG subclass, antigen epitope density and complement (C) incorporation were formed between 5-iodo-4-hydroxy-3-nitrophenacetyl (NIP) coupled to bovine serum albumin (BSA) and chimeric mouse-human anti-NIP monoclonal antibodies (mAb) of all four IgG subclasses. High and low epitope density IC of all four IgG subclasses induced specific granule release with C, but in the absence of C only IgG1 and IgG3 IC were functionally active. The Fc gamma and C receptors responsible for IgG IC-induced specific granule release and IC binding were determined using mAb specific for the ligand binding sites of CD16, CD32 and CR3, and recombinant soluble CR1. Each defined IC displayed a unique pattern of receptor preference, dependent upon subclass and antigenic epitope density. IC binding and IC-induced specific granule release was not mediated by the same receptor, or combination of receptors. High and low epitope density IgG3 IC binding and induction of specific granule release was mediated predominantly via CD16. Other IC subclasses bound differently, i.e. IgG1 IC used CD16 and CR3; IgG2 and IgG4 predominantly used complement receptors; but all three induced specific granule release via CD32. In vivo these results may translate into differential activation of neutrophils by soluble IC dependent upon their characteristics, leading to subtle nuances in the etiology, pathology and control of the immune response in IC-related diseases.

Do individuals with Williams syndrome have bizarre semantics? Evidence for lexical organization using an on-line task.

Williams syndrome, a neurodevelopmental disorder, has attracted a great deal of debate concerning the purported intactness of language in the face of other serious cognitive deficits. As more in-depth studies of specific aspects of WS language have emerged, the notion of a preserved language module has been seriously challenged. Although WS vocabulary scores are often impressive, several investigators have claimed the WS semantics are aberrant. All studies hitherto have been based on off-line experiments which necessarily involve metalinguistic processes. This clearly affects the performance of individuals with cognitive deficits. We report here an on-line study probing the semantic structure of the WS lexicon, using a task-semantic priming-which minimises metalinguistic demands. We show that WS subjects display the same taxonomic/category and thematic/functional priming effects as normal controls. The results are discussed in terms of the differences between receptive and expressive language, as well as the fact that although semantic memory and the automatic access to semantic information for individual words is normal in WS, the integration of semantic information into sentence comprehension may be abnormal. The importance of online tasks to highlight such differences is stressed.