Hypergammaglobulinemia and autoantibody induction mechanisms in viral infections

Polyclonal hypergammaglobulinemia is a characteristic of chronic inflammatory conditions, including persisting viral infections and autoimmune diseases. Here we have studied hypergammaglobulinemia in mice infected with lymphocytic choriomeningitis virus (LCMV), which induces nonspecific immunoglobulins as a result of switching natural IgM specificities to IgG. The process is dependent on help from CD4+ T cells that specifically recognize LCMV peptides presented by B cells on major histocompatibility complex class II molecules. Thus, hypergammaglobulinemia may arise when specific helper T cells recognize B cells that have processed viral antigens irrespective of the B cell receptor specificity. This nonspecific B cell activation may contribute to antibody-mediated autoimmunity.     

Human TLR-7-, -8-, and -9-mediated induction of IFN-alpha/beta and -lambda Is IRAK-4 dependent and redundant for protective immunity to viruses

Five TLRs are thought to play an important role in antiviral immunity, sensing viral products and inducing IFN-alpha/beta and -lambda. Surprisingly, patients with a defect of IRAK-4, a critical kinase downstream from TLRs, are resistant to common viruses. We show here that IFN-alpha/beta and -lambda induction via TLR-7, TLR-8, and TLR-9 was abolished in IRAK-4-deficient blood cells. In contrast, IFN-alpha/beta and -lambda were induced normally by TLR-3 and TLR-4 agonists. Moreover, IFN-beta and -lambda were normally induced by TLR-3 agonists and viruses in IRAK-4-deficient fibroblasts. We further show that IFN-alpha/beta and -lambda production in response to 9 of 11 viruses tested was normal or weakly affected in IRAK-4-deficient blood cells. Thus, IRAK-4-deficient patients may control viral infections by TLR-3- and TLR-4-dependent and/or TLR-independent production of IFNs. The TLR-7-, TLR-8-, and TLR-9-dependent induction of IFN-alpha/beta and -lambda is strictly IRAK-4 dependent and paradoxically redundant for protective immunity to most viruses in humans.     

Localization of dopamine-1 receptors along the microdissected rat nephron

Dopamine exerts numerous actions on the kidney but the precise location of its receptor subtypes along the nephron is unknown. Using a microassay we determined the specific binding of ¹²⁵I-Sch 23982, a specific and selective dopamine-1 (DA₁) receptor antagonist, to microdissected glomeruli and tubule segments. Binding of ¹²⁵I-Sch 23982 in the proximal convoluted tubule (PCT) was timeand concentration dependent, saturable and reversible. The linear Scatchard plot of saturation experiments suggested binding to a single site with an apparent K _d of 16.7 nM and B _max of 0.4 fmol·mm^–1 in the PCT, and 6.2 nM and 0.1 fmol·mm^–1 in the cortical collecting tubule (CCT). Mapping of DA₁ binding sites along the nephron revealed their presence in each of the segments examined, albeit in markedly different concentrations: the highest specific binding was measured in PCT followed by the pars recta. Binding was less in the distal nephron, and least in the medullary and cortical thick ascending limb. Modest binding was also detected in glomeruli. In cortical collecting tubules competition studies with unlabeled dopamine and probes for DA₁ (Sch 23390, fenoldopam), DA₂ (domperidone, S-sulpiride), serotonergic (serotonin, ketanserin, mianserin), and -(phentolamine) and -(propranolol) adrenergic receptors indicated a rank-order potency for displacement of ¹²⁵I-Sch 23982 binding, consistent with labeling of DA₁ receptors. Dopamine inhibited Na/K-ATPase both in PCT and CCT, an effect duplicated in the latter segment by the DA₁ agonist fenoldopam, and blocked by the DA₁ antagonist Sch 23390. These results demonstrate specific DA₁ binding sites in a nonhomogeneous pattern along the entire nephron, and suggest that dopamine may exert its effect on Na transport in distal as well as in proximal nephron segments.     

Phosphorylated KDR is expressed in the neoplastic and stromal elements of human renal tumours and shuttles from cell membrane to nucleus

Vascular endothelial growth factor (VEGF)-A is an important angiogenic factor in establishing the vasculature in renal cell carcinomas (RCCs). Since little is known about VEGF signalling in RCCs, the profile of phosphorylated KDR (pKDR) has been investigated and the intracellular location of the receptor has been examined in the present study. Using two monoclonal antibodies raised against the phosphorylated KDR epitopes (Y1059 and Y1214) known to mediate different VEGF functions, together with a commercial anti-KDR antibody and immunohistochemistry, the expression of pKDR was investigated in a series of normal (n = 25) and neoplastic kidneys (n = 54; clear cell n = 35; papillary n = 10; oncocytomas n = 8). pKDR was present in many tissue elements of both normal and neoplastic renal tissues, with strong expression in the cell membrane, cytoplasm, and nuclei of normal kidney and tumour cells, as well as endothelial cells in tumours of all histological types. Patterns and intensity were similar using both anti-pKDR antibodies. There was no significant correlation in clear cell carcinomas between pKDR expression and age (p = 0.57), tumour size (p = 0.2), gender (p = 0.59), grade (p = 0.2) or histological type (p = 0.36). To delineate further the intracellular processing that might account for the cellular distribution, confocal microscopy was also performed. Antibodies to the different phosphorylated epitopes demonstrated different intracellular staining patterns. This study shows that pKDR is present in a wide variety of renal tumours, suggesting that anti-VEGF therapy might have direct effects on tumour cells. It further suggests that cells traffic pKDR depending on the precise KDR tyrosines that are autophosphorylated in a manner that enables receptor activation to result in different functions.     

APC I1307K and the E1317Q variants are not present in Chinese colorectal cancer patients.

PURPOSE: The APC I1307K and E1317Q variants predispose to colorectal adenomas and carcinomas in Caucasians, but data are lacking in Asians. METHODS AND RESULTS: We sequenced the APC gene from codons 1261 to 1409 and found none of 147 Chinese, 20 Malay, and 11 Indian colorectal cancer patients in Singapore to carry the APC I1307K or E1317Q variants. CONCLUSION: These variants are rare in these Asian populations, and play little role in colorectal cancer causation in Chinese.     

The inversion effect on gaze perception reflects processing of component information

When faces are turned upside-down they are much more difficult to recognize than other objects. This "face inversion effect" has often been explained in terms of configural processing, which is impaired when faces are rotated away from the upright. Here we report a "gaze inversion effect" and discuss whether it is related to configural face processing of the whole face. Observers reported the gaze locations of photographed upright or inverted faces. When whole faces were presented, we found an inversion effect both for constant errors and observer sensitivity. These results were closely replicated when only the eyes were visible. Together, our findings suggest that gaze processing is largely based on component-based information from the eye region. Processing this information is orientation-sensitive and does not seem to rely on configural processing of the whole face.     

Genes encoded in the major histocompatibility complex affecting the generation of peptides for TAP transport

The B cell line 721.174 has lost the ability to present intracellular antigens to major histocompatibility complex (MHC) class I-restricted cytotoxic T lymphocytes (CTL). This phenotype results from a homozygous deletion in the MHC that includes the peptide transporter genes TAP1 and TAP2, and the proteasome subunits LMP2 and LMP7. Recent work has shown that such cells transfected with TAP genes load their class I molecules with endogenous peptides, and present several viral epitopes to class I-restricted CTL. These data implied that the LMP2 and LMP7 genes were not required for the presentation of most epitopes through class I molecules. By contrast, while confirming the previous reports, we have identified several epitopes that appear to require genes in the MHC in addition to the TAP for their presentation. Further analysis localizes the defect to proteolysis in the cytosol. In one case, presentation could be partially restored by re-expression of full-length LMP7. Control experiments with LMP7, from which the putative pro-region had been removed, failed to restore presentation, and this lack of effect correlated with failure of the shortened LMP7 to incorporate into the proteasome. These results suggest a role for LMP7 in the generation of a viral epitope, but leave open the possibility that additional genes within the .174 deletion are required for full restoration of antigen presentation.