IL-4 promotes the migration of circulating B cells to the spleen and increases splenic B cell survival

We report that IL-4 causes a redistribution of B cells and modestly increases B cell life span. Intravenous injection of a long-acting formulation of IL-4 induces increases in both spleen cell number and the percentage of splenic B cells. These effects are observed within 1 day of IL-4 administration and plateau after approximately 3 days if IL-4 treatment is continued. The increase in splenic B cell number is IL-4 dose dependent, CD4+ T cell independent, FcgammaRII/FcgammaRIII independent, and Stat6 independent. Decreases in the number of B cells in the blood and the percentage of mature B cells in the bone marrow, concomitant with the increase in splenic B cell number, suggest that redistribution of circulating B cells to the spleen is partially responsible for IL-4 induction of splenic B cell hyperplasia. Considerable reduction in the effect of 5 days of IL-4 treatment on splenic B cell number when B lymphopoiesis is blocked with anti-IL-7 mAb suggests that generation of new B cells is also involved in IL-4-induced splenic B cell hyperplasia. 5-Bromo-2'-deoxyuridine labeling experiments demonstrate that IL-4 modestly prolongs the life span of newly generated splenic B cells, and experiments that measure B cell HSA (CD24) expression as an indicator of B cell age suggest that IL-4 may also prolong the life span of mature splenic B cells. Thus, IL-4 increases splenic B cell number through two Stat6-independent effects: increased net migration of circulating B cells to the spleen and increased B cell life span. Both effects may promote Ab responses to a systemic Ag challenge.     

Computer-assisted analysis of molecular mimicry between human papillomavirus 16 E7 oncoprotein and human protein sequences

The immunology of human papillomavirus (HPV) infections has peculiar characteristics. The long latency for cervical cancer development after primary viral infection suggests mechanisms that may aid the virus in avoiding the host immunosurveillance and establishing persistent infections. In order to understand whether molecular mimicry phenomena might explain the ability of HPV to avoid a protective immune response by the host cell, sequence similarity between HPV16 E7 oncoprotein and human self-proteins was examined by computer-assisted analysis. Data were obtained showing that the HPV16 E7 protein has high and widespread similarity to several human proteins involved in a number of critical regulatory processes. In addition, multiple identical and different E7 peptide motifs are present in the same human protein. Thus, sharing of common motifs between viral oncoproteins and molecules of normal cells may be one cause underlying the scarce immunogenicity of HPV infections. The hypothesis is advanced that synthetic peptides harbouring viral motifs not and/or scarcely represented in the host's cellular proteins may represent a valuable immunotherapeutic approach for cervical cancer treatment.     

Adherence and intracellular parasitism of Paracoccidioides brasiliensis in Vero cells

Paracoccidioides brasiliensis is a dimorphic fungus known to produce invasive systemic disease in humans. The 43-kDa glycoprotein of P. brasiliensis is the major diagnostic antigen of paracoccidioidomycosis and may act as a virulence factor, since it is a receptor for laminin.Very little is known about early interactions between this fungus and the host cells, so we developed in vitro a model system employing cultured mammalian cells (Vero cells), in order to investigate the factors and virulence mechanisms of P.brasiliensis related to the adhesion and invasion process. We found that there is a permanent interaction after 30 min of contact between the fungus and the cells. The yeasts multiply in the cells for between 5 and 24 h. Different strains of P. brasiliensis were compared, and strain 18 (high virulence) was the most strongly adherent, followed by strain 113 (virulent), 265 (considered of low virulence) and 113M (mutant obtained by ultraviolet radiation, deficient in gp43). P. brasiliensis adhered to the epithelial cells by a narrow tube, while depressions were noticed in the cell surface, suggesting an active cavitation process. An inhibition assay was performed and it was verified that anti-gp43 serum and a pool of sera from individuals with paracoccidioidomycosis were able to inhibit the adhesion of P. brasiliensis to the Vero cells. Glycoprotein 43 (gp43) antiserum abolished 85% of the binding activity of P. brasiliensis. This fungus can also invade the Vero cells, and intraepithelial parasitism could be an escape mechanism in paracoccidioidomycosis.     

Natural killer cell dysfunction is a distinguishing feature of systemic onset juvenile rheumatoid arthritis and macrophage activation syndrome

Macrophage activation syndrome (MAS) has been reported in association with many rheumatic diseases, most commonly in systemic juvenile rheumatoid arthritis (sJRA). Clinically, MAS is similar to hemophagocytic lymphohistiocytosis (HLH), a genetic disorder with absent or depressed natural killer (NK) function. We have previously reported that, as in HLH, patients with MAS have profoundly decreased NK activity, suggesting that this abnormality might be relevant to the pathogenesis of the syndrome. Here we examined the extent of NK dysfunction across the spectrum of diseases that comprise juvenile rheumatoid arthritis (JRA). Peripheral blood mononuclear cells (PBMC) were collected from patients with pauciarticular (n = 4), polyarticular (n = 16), and systemic (n = 20) forms of JRA. NK cytolytic activity was measured after co-incubation of PBMC with the NK-sensitive K562 cell line. NK cells (CD56+/T cell receptor [TCR]-alphabeta-), NK T cells (CD56+/TCR-alphabeta+), and CD8+ T cells were also assessed for perforin and granzyme B expression by flow cytometry. Overall, NK cytolytic activity was significantly lower in patients with sJRA than in other JRA patients and controls. In a subgroup of patients with predominantly sJRA, NK cell activity was profoundly decreased: in 10 of 20 patients with sJRA and in only 1 of 20 patients with other JRA, levels of NK activity were below two standard deviations of pediatric controls (P = 0.002). Some decrease in perforin expression in NK cells and cytotoxic T lymphocytes was seen in patients within each of the JRA groups with no statistically significant differences. There was a profound decrease in the proportion of circulating CD56bright NK cells in three sJRA patients, a pattern similar to that previously observed in MAS and HLH. In conclusion, a subgroup of patients with JRA who have not yet had an episode of MAS showed decreased NK function and an absence of circulating CD56bright population, similar to the abnormalities observed in patients with MAS and HLH. This phenomenon was particularly common in the systemic form of JRA, a clinical entity strongly associated with MAS.     

Sheets of Vertically Aligned BaTiO3 Nanotubes Reduce Cell Proliferation but Not Viability of NIH-3T3 Cells

All biomaterials initiate a tissue response when implanted in living tissues. Ultimately this reaction causes fibrous encapsulation and hence isolation of the material, leading to failure of the intended therapeutic effect of the implant. There has been extensive bioengineering research aimed at overcoming or delaying the onset of encapsulation. Nanotechnology has the potential to address this problem by virtue of the ability of some nanomaterials to modulate interactions with cells, thereby inducing specific biological responses to implanted foreign materials. To this effect in the present study, we have characterised the growth of fibroblasts on nano-structured sheets constituted by BaTiO₃, a material extensively used in biomedical applications. We found that sheets of vertically aligned BaTiO₃ nanotubes inhibit cell cycle progression - without impairing cell viability - of NIH-3T3 fibroblast cells. We postulate that the 3D organization of the material surface acts by increasing the availability of adhesion sites, promoting cell attachment and inhibition of cell proliferation. This finding could be of relevance for biomedical applications designed to prevent or minimize fibrous encasement by uncontrolled proliferation of fibroblastic cells with loss of material-tissue interface underpinning long-term function of implants.     

Polymorphism of S-adenosylhomocysteine hydrolase in Italy

S-adenosylhomocysteine hydrolase (SAHH) polymorphism has been investigated in the Italian population. Three common alleles, SAHH*1, SAHH*2 and SAHH*3, have been observed and the estimated gene frequencies are 0.968, 0.023 and 0.009, respectively. SAHH activity has been assayed in 50 healthy individuals and the mean activity was 0.043 +/- 0.017 mumol uric acid/min/g Hb at 37 degrees C. Five heterozygotes for adenosine deaminase deficiency and three heterozygotes for purine nucleoside phosphorylase deficiency showed SAHH within the range of the normal distribution. The effects of some thiol reagents on red blood cell SAHH electrophoretic pattern have been investigated.     

Inhibition of microsomal lipid peroxidation by naphthoquinones: structure-activity relationships and possible mechanisms of action

Menadione (2-methyl-1,4-naphthoquinone) is a remarkably potent inhibitor of microsomal lipid peroxidation, effective at submicromolar concentrations. Its possible mechanism of action and the relationship between naphthoquinone structure and antioxidant activity were the topics of this investigation. In the microsomal lipid-peroxidizing system dependent on NADPH and ferric pyrophosphate, menadione, at concentrations of 50 microM or higher virtually eliminated the accumulation of malondialdehyde and lipid hydroperoxides. In the NADPH-independent, cumene hydroperoxide-dependent system, menadione was also an effective antioxidant, but only in the presence of reducing equivalents. These and other observations indicate that a reduced form of menadione, either the hydroquinone or semiquinone, is the active antioxidant, and suggest that it may trap hydroperoxy radicals, alkoxy radicals, or other free radicals involved in propagating lipid peroxidation. Moreover, these results show that electron diversion per se cannot account for the antioxidant effects of menadione. A comparison of the antioxidant activities of eight 1,4-naphthoquinones indicated that methyl substitution of C-2, lack of steric hindrance at C-3 or C-5, and (in the case of weak acids) a relatively high pKa are favorable structural features associated with strong antioxidant activity.