In vitro test on the ability of a yeast cell wall based product to inhibit the Escherichia coli F4ac adhesion on the brush border of porcine intestinal villi.

The ability of a yeast cell wall (YCW)-based product (SENTIGUARD C; Nutriad) to inhibit the enterotoxigenic Escherichia coli F4ac (ETEC) adhesion on the brush border of porcine intestinal villi was tested. The ETEC suspensions were preincubated with 2 batches of the product (A and B) at different concentrations (10, 5, and 0.5%, wt/vol) or with their filtrates (AF and BF) and then with intestinal villi susceptible to ETEC adhesion. In all the trials, ETEC suspensions were also preincubated with egg yolk (E) immunized against ETEC to assess the maximum inhibition of the adhesiveness or directly with the villi [control group (Con)] to verify the maximum adhesiveness of the pathogen. For each treatment, 20 different villi were observed, brush border measured, and the adherent pathogens counted. A scanning electron microscope analysis was used to confirm the ability of ETEC to adhere on the YCW. The E treatment significantly reduced the pathogen adhesion on the villi compared with the C group in all the trials (P < 0.001). Both batches of SENTIGUARD C significantly reduced the pathogen adhesion on the villi compared with the C group at the concentration of 10 and 5% (P < 0.001) but not at the concentration of 0.5%. The BF did not significantly reduce the ETEC adhesion whereas the AF significantly increased bacterial adhesion (P = 0.015). The microscopy results confirm the ability of ETEC to adhere on YCW. Taken together, our results indicate the ability of the SENTIGUARD C to contain the intestinal infection from ETEC in young pigs with the affinity of ETEC to YCW.

Regulation of immunoglobulin light chain gene rearrangements during early B cell development in the human.

Southern blot analyses of immunoglobulin light chain gene rearrangements in human leukemias and myelomas indicated that lambda loci in kappa-producing cells are largely unrearranged while kappa loci in lambda producers are often rearranged and inactivated by rearrangements of the kappa-deleting element (KDE). For a systematic analysis of the regulation of light chain rearrangements during early B cell development in normal human B cells also considering functionality of the rearrangements, we used FACS-sorted single naive kappa- and lambda-expressing B cells from peripheral blood of healthy humans. V(kappa)J(kappa) and V(lambda)J(lambda) joints and rearrangements involving the KDE were amplified simultaneously from single cells and sequenced. Whereas only 2 - 3 % of kappa-expressing cells carry V(lambda)J(lambda) joints, nearly all lambda-expressing cells have rearranged kappa loci and indeed carry V(kappa)J(kappa) joints. The V(kappa)J(kappa) joints in lambda-expressing cells exhibit preferential J(kappa)4 and J(kappa)5 over J(kappa)1 and J(kappa)2 usage compared to kappa-expressing cells. Thirty percent of the V(kappa)J(kappa) joints in lambda producers are rearranged in-frame. These data indicate extensive sequential V(kappa)-J(kappa) rearrangements and inactivation of functional V(kappa)J(kappa) joints in lambda-expressing cells, presumably before V(lambda)J(lambda) joining.

Receptor revision plays no major role in shaping the receptor repertoire of human memory B cells after the onset of somatic hypermutation.

In order to determine whether V gene replacement accompanies somatic hypermutation in the germinal center (GC) reaction in the human, we analyzed V(kappa)J(kappa) and V(lambda)J(lambda) joints and the kappa-deleting element in single lambda(+) naive and post GC B cells for rearrangements at the kappa and lambda loci. Among 265 lambda(+) post GC B cells, not a single unequivocal and only two potential examples of a cell that switched to lambda light chain expression after accumulation of (unfavorable) mutations in its productive V(kappa) rearrangement were observed. Taking the PCR efficiency into account, the frequency of such cells is likely below 3 %. In addition, heavy and light chain gene rearrangements were amplified and sequenced from the oligoclonal population of IgD-only peripheral blood post GC B cells which display extensive intraclonal sequence diversity. Among 61 IgD-only B cells belonging to 15 clones with intraclonal diversity, no combination of V gene rearrangements indicating receptor revision during clonal expansion was observed. Moreover, among 124 and 49 V(H) genes amplified from IgD-only and class-switched B cells, respectively, not a single example of V(H) revision through V(H) hybrid generation was detected. These results suggest that in the human GC reaction V gene replacement either does not usually accompany somatic hypermutation or is mostly counterselected.

Hypermutation of multiple proto-oncogenes in B-cell diffuse large-cell lymphomas.

Genomic instability promotes tumorigenesis and can occur through various mechanisms, including defective segregation of chromosomes or inactivation of DNA mismatch repair. Although B-cell lymphomas are associated with chromosomal translocations that deregulate oncogene expression, a mechanism for genome-wide instability during lymphomagenesis has not been described. During B-cell development, the immunoglobulin variable (V) region genes are subject to somatic hypermutation in germinal-centre B cells. Here we report that an aberrant hypermutation activity targets multiple loci, including the proto-oncogenes PIM1, MYC, RhoH/TTF (ARHH) and PAX5, in more than 50% of diffuse large-cell lymphomas (DLCLs), which are tumours derived from germinal centres. Mutations are distributed in the 5' untranslated or coding sequences, are independent of chromosomal translocations, and share features typical of V-region-associated somatic hypermutation. In contrast to mutations in V regions, however, these mutations are not detectable in normal germinal-centre B cells or in other germinal-centre-derived lymphomas, suggesting a DLCL-associated malfunction of somatic hypermutation. Intriguingly, the four hypermutable genes are susceptible to chromosomal translocations in the same region, consistent with a role for hypermutation in generating translocations by DNA double-strand breaks. By mutating multiple genes, and possibly by favouring chromosomal translocations, aberrant hypermutation may represent the major contributor to lymphomagenesis.

Somatic hypermutation in normal and transformed human B cells.

In the human, most IgM+IgD+ as well as CD5+ peripheral blood B cells express unmutated V genes and thus can be assigned to a pre-germinal centre (GC) stage of development. The memory B-cell compartment generated in the GC reaction and characterized by cells bearing somatically mutated V-region genes consists not only of class-switched cells, but also of IgM-only B cells and perhaps a subset of IgM+IgD+B cells expressing the CD27 antigen. Comparison of the rearranged V-region genes of human B-cell lymphomas with those of the normal B-cell subsets allows the identification of the progenitor cells of these tumours in terms of their stage of maturation. On this basis, most B-cell non-Hodgkin lymphomas, and in addition Hodgkin and Reed-Sternberg (HRS) cells in Hodgkin's disease (HD), are derived from B cells at a GC or post-GC stage of development. The mutation pattern indicates that the precursors of the tumour clones have been stringently selected for expression of a functional antigen receptor with one notable exception: HRS cells in classical (but not lymphocyte-predominant) HD appear to be derived from "crippled" GC B cells. Sequence analysis of rearranged V genes amplified from single tonsillar GC B cells revealed that the somatic hypermutation process introduces deletions and/or insertions into V-region genes more frequently than indicated by previous investigations. Presumably, this feature of the hypermutation mechanism is often responsible for the generation of heavy chain disease, and also several types of chromosomal translocations of oncogenes into immunoglobulin loci in human B-cell lymphomas.

Frequent occurrence of deletions and duplications during somatic hypermutation: implications for oncogene translocations and heavy chain disease.

Human naive and germinal center (GC) B cells were sorted by flow cytometry and rearranged VH region genes were amplified and sequenced from single cells. Whereas no deletions or insertions were found in naive B cells, approximately 4% of in-frame and >40% of out-of-frame rearrangements of GC B cells harbored deletions and/or insertions of variable length. The pattern of deletions/insertions and their restriction to mutated V genes strongly suggests that they result from somatic hypermutation. Deletions and insertions account for approximately 6% of somatic mutations introduced into rearranged VH region genes of GC B cells. These deletions/insertions seem to be the main cause for the generation of heavy chain disease proteins. Furthermore, it appears that several types of oncogene translocations (like c-myc translocations in Burkitt's lymphoma) occur as a byproduct of somatic hypermutation within the GC-and not during V(D)J recombination in the bone marrow as previously thought.

Analgesics abuse: theoretical and practical considerations.

Three important issues must be addressed in any attempt to determine whether combination painkillers play a role in analgesic nephropathy. The first issue, namely that of a causal link between the combination itself and nephrotoxicity, has never been adequately documented. On the contrary, there is much evidence that the combination as such has no influence whatsoever. The cause of the nephrotoxicity is most likely the painkilling mechanism, i.e. the antagonism to prostaglandins; the most potent prostaglandin-antagonists, the non-steroidal anti-inflammatory drugs, whether used in combination or singly, also most frequently cause renal pathology. The second issue, i.e. the safety of combination painkilling drugs in comparison with that of single substances, is intimately bound up with the advantages of the former with respect to both activity and the activity-side-effects ratio. The third issue, abuse, should be recast in a broader context. The central element here is not the painkilling drug but rather the labile personality of the user in conjunction with a more or less stressful environment in which a wide variety of drugs and stimulants are available and taken for better 'coping'. To a great extent analgesics abuse can be prevented by information (i.e. social medicine). In a broader perspective, man experiences considerable difficulty adapting to the sweeping social, technological and ideological changes of recent decades, and this transition contributes in no small measure to the analgesics problem. It should be a priority of government to find remedies for this state of affairs.