Despite its widespread distribution on both lymphoid and myeloid cells, the biological role of the low-affinity immunoglobulin-G receptor, Fc gamma RII, is not fully understood. Defects in this receptor or its signalling pathway in B cells result in perturbations in immune-complex-mediated feedback inhibition of antibody production. We now report that Fc gamma RII-deficient animals display elevated immunoglobulin levels in response to both thymus-dependent and thymus-independent antigens. Additionally, the effector arm of the allergic response is perturbed in these mice. Mast cells from Fc gamma RII-/- are highly sensitive to IgG-triggered degranulation, in contrast to their wild-type counterparts. Fc gamma RII-deficient mice demonstrate an enhanced passive cutaneous analphylaxis reaction, the result of a decreased threshold for mast-cell activation by Fc gamma RIII cross-linking. These results demonstrate that Fc gamma RII acts as a general negative regulator of immune-complex-triggered activation in vivo for both the afferent and efferent limbs of the immune response. Exploiting this property offers new therapeutic opportunities for the treatment of allergic and autoimmune disorders.

Recombination activating genes (RAG-1 and RAG-2), involved in V(D)J rearrangement of immunoglobulin genes, have been thought to be expressed only in immature stages of B-cell development. However, RAG-1 and RAG-2 transcripts were found to be reexpressed in mature mouse B cells after culture with interleukin-4 in association with several different co-stimuli. Reexpression was also detected in draining lymph nodes from immunized mice. RAG-1 and RAG-2 proteins could be detected by immunofluorescence microscopy in the nuclei of B cells cultured in vitro and in the germinal centers of draining lymph nodes. These findings suggest that RAG gene products play a heretofore unsuspected role in mature B cells.The rearrangement of immunoglobulin (Ig) and T cell receptor (TCR) genes is a crucial step in the maturation process of B cells and T cells. Recombination of Ig and TCR genes is catalyzed by the products of the two recombination activating genes, RAG-1 and RAG-2 (1-3). A defect in either RAG-1 or RAG-2 results in the retention of Ig and TCR loci in germline configuration and blocks the development of mature lymphocytes (4). RAG-1 and RAG-2 have been considered to be expressed exclusively in immature lymphocytes in bone marrow and thymus, being readily down-regulated in mature lymphocyte populations, such as IgD ϩ B cells and TCR ϩ T cells (2,5,6). RAG expression in early B cells occurs in two waves, the first being responsible for V(D)J (V, variable; D, diversity; J, joining) rearrangement of Ig heavy-chain genes in proB and preB-I cells and the second for VJ recombination of Ig light-chain genes in small preB-II cells (5). We describe a third wave of RAG-1 and RAG-2 expression, induced in activated mature B cells in vitro and in vivo.Spleen B cells from C3H/HeN mice cultured for 2 days with lipopolysaccharide (LPS) plus interleukin-4 (IL-4) expressed RAG-1 and RAG-2, as assessed by the combination of reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern (DNA) blotting (Fig. 1A). The presence of bands of correct size was strictly dependent on RT, indicating that PCR-amplified materials were not derived from contaminated genomic DNA. RAG-1 and RAG-2 expression was not detected in the cells before the culture, in unstimulated B cells, and in cells stimulated with either LPS or IL-4 alone. LPS combined with other cytokines-including IL-2, IL-3, or IL-5-was ineffective (7). To confirm that surface IgD ϩ (sIgD ϩ ) mature B cells respond to LPS plus IL-4, we undertook similar experiments in B cells purified by panning on plates coated with monoclonal antibody (mAb) to IgD (Fig. 1B). These enriched B-cell preparations also expressed RAG genes in response to LPS plus IL-4.Various stimuli other than LPS were examined for their capacity to elicit the expression of RAG genes in the presence of IL-4 (Fig. 1C). Monoclonal antibody to CD40 was as effective as LPS, and antibody to heavy chain plus 8-mercaptoguanosine, a potent B-cell activator (8), was also effective; both these stimuli were ineffective in the absen...

Bladder cancer displays an aggressive phenotype in the muscle-invasive phase, and is associated with a high mortality rate. Therefore, novel molecular therapeutic targets are needed to improve patient survival. A monoclonal antibody against the extracellular domain of the claudin-4 (CLDN4) tight junction protein was established by immunizing rats with a plasmid vector encoding human CLDN4. A hybridoma clone, producing a rat monoclonal antibody recognizing CLDN4 (clone 4D3), was obtained. Immunohistochemistry by using the 4D3 antibody showed that CLDN4 expression was associated with local invasion, nodal metastasis, distant metastasis, and advanced stage in 86 cases of bladder cancer. The 4D3 antibody inhibited growth, invasion, and survival, associated with abrogation of the intratumoral microenvironment; lowered concentrations of epidermal growth factor and vascular endothelial growth factor were found in three-dimensional cultures of T24 and RT4 cells. In combination with cisplatin therapy, 4D3 enhanced cisplatin cytotoxicity by increasing cellular permeability, leading to increased intracellular cisplatin concentrations. In mouse models of subcutaneous tumors and lung metastasis, 4D3 enhanced tumor growth inhibition, alone and with concurrent cisplatin treatment. The anti-tumor activity of the newly established 4D3 antibody suggests that it may be a powerful tool in CLDN4-targeting therapy, and in combination with chemotherapy.

Melanoma inhibitory activity (MIA) is an 11-kDa secretory protein isolated from malignant melanoma cells that is correlated with invasion and metastasis in various human malignancies. We examined MIA expression in 62 oral squamous cell carcinomas (OSCC) by immunohistochemistry. MIA expression was significantly associated with nodal metastasis (P = 0.00018). MIA expression was also associated with expression of high mobility group box-1 (HMGB1) (P < 0.0001) and lymph vessel density (P < 0.0001). Expression levels of MIA, HMGB1, nuclear factor kB (NFkB) p65 and HMGB1-NFkB p65 binding were significantly higher in a metastatic human OSCC cell line (HSC3) than those in a non-metastatic OSCC cell line (HSC4). H ead and neck cancer is the sixth most common malignancy worldwide and the first leading cause of cancer death in South Asia.(1) About 300 000 patients develop OSCC every year in the world.(2,3) OSCC has a high potential for nodal metastasis and locoregional invasion, (4) from which over 50% of patients die.(5,6) To control lymph-node metastasis of OSCC, we need to study the molecular aspects of the mechanism of metastasis.MIA is an 11-kDa secretory protein isolated from supernatants of HTZ-19 malignant melanoma cells, (7,8) the gene locus of which is mapped to chromosome 19q13.32-13.33.(9) Although previous reports indicated that MIA is correlated with invasion and metastasis in malignant melanoma, (10)(11)(12) breast cancer,chondrosarcoma, (13) glioma, (14) and pancreatic cancer,the definite functions of MIA for cancer cells are still unclear.HMGB1 has a dual role as an extracellular secretory protein and a chromosomal structural protein.(16) HMGB1 works as a cytokine or a growth factor in neural ontogenesis, septic inflammation and neoplasm. HMGB1 is also considered an amphoterin, which is isolated as a motility factor in neurite outgrowth.(17) We previously reported coexpression of HMGB1 and receptor for advanced glycation end products (RAGE), which is a major membrane receptor for HMGB1 and is significantly associated with tumor progression and metastasis (18)(19)(20)(21)(22)(23)(24) and suppression of tumor-associated macrophages. (25,26) As a chromatin structural protein, HMGB1 participates in gene expression, DNA repair and functions of the p53 family.(27) Recently, HMGB1 was revealed to interact with NFkB p65 to accelerate MIA expression. (28,29) HMGB1 and NFkB p65 concurrently bind to a 30-bp region in the promoter region of the MIA gene designated as the highly conserved region (HCR).MIA is suspected to play an important role as a pro-metastatic factor in HMGB1-overexpressing cancers. In the present study, we analyzed the relationship between MIA expression and nodal metastasis and HMGB1 expression in human OSCC. Materials and MethodsTumor specimens. Sixty-two formalin-fixed, paraffin-embedded specimens of primary OSCC were randomly selected at Nara Medical University Hospital, Kashihara, Japan. None of the samples was treated using neo-adjuvant therapy. Medical records and prognostic follow-up data w...

We have isolated a cDNA clone encoding a novel murine cell-surface glycoprotein. This polypeptide is predicted to be composed of a signal peptide of 23 amino acids, an extracellular region of 620 amino acids that contains six immunoglobulin-like domains with five potential N-glycosylation sites, a transmembrane sequence of 20 amino acids, and a cytoplasmic tail of 178 amino acids with four sets of sequences similar to the immunoreceptor tyrosine-based inhibition motif. The relative molecular mass of the mature polypeptide is calculated to be 90,520 Da. The polypeptide, designated as p91, shows striking homologies to human killer cell inhibitory receptors, a murine gp49B1 protein, a bovine Fc␥2 receptor, and a human Fc␣ receptor. The mRNA of p91 was especially abundant in murine macrophages. Western blot analysis using p91-specific anti-peptide sera detected a 130-kDa polypeptide in macrophages. Surface biotinylation and immunoprecipitation analysis verified the surface expression of the translation products on COS-1 cells transfected with the p91 cDNA, but the cells failed to show any Fc binding activity.