BAFF and LPS cooperate to induce B cells to become susceptible to CD95/Fas-mediated cell death.

Microorganisms with pathogen-associated molecular patterns (PAMP) activate B cells directly by binding to TLR and also indirectly by inducing APC to release cytokines such as BAFF that promote B cell survival. We found that murine B cells activated concomitantly with LPS (TLR-4 ligand) and BAFF are protected from spontaneous apoptosis, but are more susceptible to Fas/CD95-mediated cell death. This increased susceptibility to Fas-induced apoptosis is associated with a dramatic coordinated up-regulation of Fas/CD95 and IRF-4 expression through a mechanism mediated, at least in part, by inhibition of the MEK/ERK pathway. Up-regulation of Fas/CD95 by BAFF is restricted to B cells activated through TLR-4, but not through TLR-9, BCR or CD40. TLR ligands differ in the BAFF family receptors (R) they induce on B cells: BAFF-R is increased by the TLR4 ligand, LPS, but not by the TLR9 ligand, CpG-containing oligodeoxynucleotides, which, in contrast, strongly up-regulates transmembrane activator and CAML interactor (TACI). This suggests the up-regulation of Fas by BAFF is mediated by BAFF-R and not by TACI. Consistently, APRIL, which binds to TACI and B cell maturation antigen but not BAFF-R, did not enhance Fas expression on LPS-activated B cells. Increased susceptibility to Fas-mediated killing of B cells activated with LPS and BAFF may be a fail-safe mechanism to avoid overexpansion of nonspecific or autoreactive B cells.

Comparison of antagonistic ability against enteropathogens by G+ and G- anaerobic dominant components of human fecal microbiota.

To confirm if anaerobic G+-components are those responsible for the function of colonization resistance, obligate anaerobic G+- and G- -bacteria from normal dominant microbiota of human feces were isolated from three successive collections and then used in in vitro assays for antagonism against two enteropathogenic bacteria. The production of inhibitory diffusible compounds was determined on supplemented BHI agar and MRS agar media for G- - and G+-bacteria, respectively. Salmonella enterica subsp. enterica serovar Typhimurium and Shigella sonnei were used as indicators. G+-bacteria presented a higher overall antagonistic frequency against both pathogenic bacteria (57 and 64 % for S. enterica serovar Typhimurium and S. sonnei, respectively) when compared to G+-microorganisms but with a quite elevated variation between volunteers (0-100 %) and collection samples (40-72 and 40-80 % for S. enterica sv. Typhimurium and S. sonnei, respectively). On the other hand, only three among 143 G- -isolates tested showed antagonistic activity. The results showed that, at least in vitro, obligate anaerobic G+-components of the dominant human fecal microbiota present a higher potential for antagonism against the enteropathogenic models tested than do G- -bacteria.

Two different late embryogenesis abundant proteins from Arabidopsis thaliana contain specific domains that inhibit Escherichia coli growth.

Late embryogenesis abundant (LEA) proteins constitute a set of proteins widespread in the plant kingdom that show common physicochemical properties such as high hydrophilicity and high content of small amino acid residues such as glycine, alanine, and serine. Typically, these proteins accumulate in response to water deficit conditions imposed by the environment or during plant normal development. In this work, we show that the over-expression in Escherichia coli of proteins of the LEA 2 and the LEA 4 families from Arabidopsis thaliana leads to inhibition of bacterial growth and that this effect is dependent on discrete regions of the proteins. Our data indicate that their antimicrobial effect is achieved through their interaction with intracellular targets. The relevance of the cationic nature and the predicted structural organization of particular protein domains in this detrimental effect on the bacteria growth process is discussed.

[In vitro evaluation of antibacterial substances produced by bacteria isolated from different marine organisms]. / Evaluación in vitro de sustancias antibacterianas producidas por bacterias aisladas de diferentes organismos marinos.

Bacteria from several groups of marine organisms were isolated and, using direct antibiograms, identified those that produce antibacterial substances, using a human pathogenic strain of Staphylococcus aureus ATCC6538 as revealing microorganism. Bacteria which produce substances that inhibited S. aureus growth were identified through morphological, physiological and biochemical tests. Out of 290 bacteria, 54 (18.6%) inhibited the growth of S. aureus, but only 27 survived for identification. Bivalves, sponges and corals were the most represented from which 41.2, 33.3 and 29.7%, respectively, produced antibacterial substances of the isolated bacteria in each group. The marine species with highest proportions of these bacteria were the hard coral Madracis decactis (62.5%), the sponges Cliona sp. (57.1%) and the octocoral Plexaura flexuosa (50.0%). Out of the 27 strains that produced antibacterial substances, 51.8% were Aeromonas spp. and 14.8% Vibrio spp. Marine bacteria that produce antibacterial substances are abundant, most belong in the Vibrionacea group and were isolated mainly from corals and bivalve mollusks.

Evidence for the production of a growth-inhibitory factor by human granulosa-luteal cells.

The factors involved in the inhibition of ovarian follicular cellular growth after the luteinizing hormone (LH) surge are poorly established. The aim of this study was to investigate the production of an inhibitory growth factor by human ovarian cells. Luteinized granulosa cells were obtained from an assisted fertilization program and were cultured in the presence or absence of follicle-stimulating hormone (FSH) and estradiol. Data obtained by cell counting showed that the number of human luteinized granulosa cells cultured in the presence of fetal bovine serum (10%) increased 1.8-fold within a 2-day period. In serum-free medium, human luteinized granulosa cells were able to incorporate 3H-thymidine, measured during consecutive 48 h periods. During all the periods tested (up to 7 days), low basal levels of thymidine incorporation were measured and were further reduced in the presence of FSH (200 ng/ml) and estradiol (500 ng/ml). To elucidate the possible production of an inhibitory growth factor, 3H-thymidine incorporation by rat granulosa cell cultures was measured in the presence of conditioned media (CM; from human granulosa cell cultures). In this system, FSH and estradiol elicited a tenfold increase in thymidine incorporation. The addition of CM (10% v/v collected on day 2) to FSH- and estradiol-treated granulosa cell cultures produced an inhibition (61%) of thymidine incorporation. The active factor in CM withstood freeze-thawing, was stable for several weeks at -20 degrees C, became unstable at 4 degrees C, and was heat labile and sensitive to proteolysis. Ultrafiltration using membranes with different molecular weight cutoffs suggested that the factor had a molecular weight > 30,000 dalton.(ABSTRACT TRUNCATED AT 250 WORDS)