IgVH gene analysis suggests that peritoneal B cells do not contribute to the gut immune system in man

The contribution of peritoneal B cells to the intestinal lamina propria plasma cell population is well documented in mice, but unknown in humans. We have analyzed immunoglobulin (Ig) genes of human peritoneal B cells, because such genes show distinctive characteristics in mucosal B cells, particularly highly mutated variable regions. Here, we report the characteristics of variable region genes used by IgM, IgA and IgG in peritoneal cells. We focused on the properties of IgV(H)4-34 to allow comparisons of like-with-like between different isotypes and cells from different immune compartments. We observed that the IgM genes were mostly unmutated, and that the mutated subset had less mutations than would be expected in a mucosal B cell population. Likewise, the IgV(H)4-34 genes used by IgA and IgG from peritoneal B cells had significantly lower numbers of mutations than observed in the mucosal counterparts. Other trends observed, while not reaching statistical significance, followed the trend of peripheral B cells. The peritoneal B cell population had more IgA1 than IgA2 sequences, and there was no dominance of J(H)4 in the IgA from peritoneum or spleen, in contrast to the mucosal sequences. Overall, this study suggested that human peritoneal B cell are either peripheral or mixed in origin; they are unlikely to represent an inductive compartment for the mucosal B cell system.     

Immunohistochemical analysis of ageing human B and T cell populations reveals an age-related decline of CD8 T cells in spleen but not gut-associated lymphoid tissue (GALT)

It is thought that senescence of the immune system is responsible, at least in part, for many health problems associated with ageing. Previous studies on changes in lymphocyte composition have used flow cytometry to study peripheral blood lymphocytes (PBL's), or cells isolated from rodent tissue, and have yielded conflicting results. We have used immunohistochemistry to determine whether the B and T cells in human tissue from spleen and gut are affected by age. Areas of germinal centre, mantle zone and marginal zone of B cell follicles were measured. In addition, CD4 and CD8 T cells in T cell areas and in B cell follicles were counted. We observed a striking age-related decrease in the proportion of CD8+ T cells in the T cell zones of the spleen. This decrease was not apparent in the T cell population that occupies splenic B cell areas, or in GALT. Further differences, in CD4+ cells, were seen between T cell populations in the T cell zones and those in B cell areas. These findings highlight differences between lymphocyte populations in different lymphoid tissues, and different compartments within each tissue, which may be of importance in future studies of the ageing immune system.     

Human MSH2 binds to trinucleotide repeat DNA structures associated with neurodegenerative diseases

The expansion of trinucleotide repeat sequences is associated with several neurodegenerative diseases. The mechanism of this expansion is unknown but may involve slipped-strand structures where adjacent rather than perfect complementary sequences of a trinucleotide repeat become paired. Here, we have studied the interaction of the human mismatch repair protein MSH2 with slipped-strand structures formed from a triplet repeat sequence in order to address the possible role of MSH2 in trinucleotide expansion. Genomic clones of the myotonic dystrophy locus containing disease-relevant lengths of (CTG)n x (CAG)n triplet repeats were examined. We have constructed two types of slipped-strand structures by annealing complementary strands of DNA containing: (i) equal numbers of trinucleotide repeats (homoduplex slipped structures or S-DNA) or (ii) different numbers of repeats (heteroduplex slipped intermediates or SI-DNA). SI-DNAs having an excess of either CTG or CAG repeats were structurally distinct and could be separated electrophoretically and studied individually. Using a band-shift assay, the MSH2 was shown to bind to both S-DNA and SI-DNA in a structure- specific manner. The affinity of MSH2 increased with the length of the repeat sequence. Furthermore, MSH2 bound preferentially to looped-out CAG repeat sequences, implicating a strand asymmetry in MSH2 recognition. Our results are consistent with the idea that MSH2 may participate in trinucleotide repeat expansion via its role in repair and/or recombination.      

The cholinergic innervation of the rat substantia nigra: a light and electron microscopic immunohistochemical study

Summary Putative cholinergic axons and synaptic endings were demonstrated in the substantia nigra (SN) of the rat by light and electron microscopy on the basis of the localization of choline acetyltransferase (ChAT) immunoreactivity. The distribution of ChAT immunoreactivity in the SN as demonstrated by light microscopy revealed a modest network of ChAT-immunoreactive beaded axons in the SNc, in comparison to a relatively sparse distribution in the SNr. These axonal profiles were most dense in the middle of the rostral-caudal extent of the SNc and appeared to be concentrated in the middle third of the medial-lateral extent. By electron microscopy, unmyelinated, small diameter (0.25 m) ChAT-immuno-reactive axons were observed interspersed among numerous other non-immunoreactive axons in the SNc. ChAT-immunoreactive synaptic endings were observed in juxtaposition to small caliber (0.5 m) non-immunoreactive dendrites, and contained numerous spheroidal synaptic vesicles and occasional mitochondria. Synaptic contact zones were characterized by an accumulation of synaptic vesicles along the presynaptic membrane, and a prominent postsynaptic densification producing an asymmetrical pre-/postsynaptic membrane profile typical of excitatory synapses. These findings provide direct evidence for a cholinergic innervation of the SN, and suggest that this input may have an excitatory effect on neuronal elements in the SNc.     

Periarteritis in a beagle colony

Primary periarteritis, an uncommon necrotizing vasculitis in the dog, was found to affect, almost exclusively, the major branches of the coronary arteries in a number of young beagle dogs. The arteritis was mainly distributed in the proximal segment of the right coronary artery. Immunocytochemical studies failed to identify immunoglobulin deposits in the lesions and the cause of the arteritis remains unknown. It is important to be aware of this spontaneous condition and its regional distribution since certain cardiovascular drugs may also produce necrotizing arteritis at similar sites.     

Activation of mucosal Vβ3+ T cells and tissue damage in human small intestine by the bacterial superantigen,Staphylococcus aureus enterotoxin B

Staphylococcus aureus enterotoxin B (SEB) was added to explants of fetal human intestine in organ culture or administered into the lumen of fetal small intestine prior to culture. Both routes produced a massive increase in lamina propria T cells expressing Vβ33, and to a lesser extent, those expressing Vβ5 and Vβ12. SEB-activated lamina propria T cells produced interleukin-2 and interferon-Y and T cell activation was accompanied by tissue damage, which was inhibited by FK506.     

Magnesium-fluoride interrelationships in man II. Effect of magnesium on fluoride metabolism

The effect of magnesium on the fluoride balance was investigated in man by determining metabolic balances of fluoride and magnesium in control studies and during magnesium supplementation. The magnesium intake averaged 264 mg/day in the control studies and 825 in the experimental studies. The studies were carried out during four calcium intakes that ranged from 200 to 2,200 mg/day and during phosphorus intakes ranging from 800 to 2,000 mg/day. The studies were carried out during a fluoride intake of about 4 mg/day that was due to the dietary fluoride content and the intake of water and during a high fluoride intake of 25 mg/day that was due to the addition of sodium fluoride. During the high magnesium intake, both the urinary and fecal magnesium excretions increased and the magnesium balances became more positive. These changes were not associated with any significant changes of either the urinary or fecal fluoride excretions or of the fluoride balances during the different intakes of calcium phosphorus, or fluoride.     

Regulation of the association between PSTPIP and CD2 in murine T cells

Prominent in T cells and natural killer cells, CD2 binding protein 1 (CD2BP1) plays an important role in CD2-mediated adhesion and signal transduction. In the current study, we investigated CD2 and PSTPIP (proline, serine, threonine phosphatase interacting protein, murine homologue of CD2BP1) interactions in purified mouse splenic T cells. PSTPIP associated with CD2 in both resting and activated T cells. Following various stimuli, such as concanavalin A, anti-TCRbeta, anti-CD3epsilon, anti-CD3epsilon/phorbol myristate acetate (PMA), IL-2, or PMA/ionomycin, PSTPIP and CD2 expression, as well as their association, increased in a time-dependent fashion. While PSTPIP expression and CD2 expression were comparable across most groups, the PSTPIP-CD2 association stimulated by anti-CD3epsilon alone was significantly greater than with other stimuli. Stimulation by anti-CD3epsilon plus anti-CD28 induced even greater PSTPIP-CD2 association than anti-CD3epsilon treatment alone, indicating that CD28 initiated signals are involved in regulating this interaction. There was no direct association between CD3epsilon or CD28 and PSTPIP. Tyrosine phosphorylated PSTPIP bound poorly to CD2 compared to dephosphorylated PSTPIP, and protein tyrosine phosphatase was shown to affect both phosphorylation of PSTPIP and the CD2-PSTPIP association. In addition to CD2, PSTPIP associated with CD4, CD8, CD54, and CD62L. CD2 and CD4 ligation reciprocally regulated their association with PSTPIP. These findings indicate that T cell activation, particularly through the CD3 and CD28 signal transduction pathways, regulates PSTPIP-CD2 interactions. PSTPIP likely has additional broader effects through interactions with CD4, CD8, CD54, and CD62L, and this may influence T cell responses to antigen.     

Transneuronal transport of peroxidase-conjugated wheat germ agglutinin (WGA-HRP) from the olfactory epithelium to the brain of the adult rat

Summary The sensory neurons of the olfactory epithelium, as a consequence of their odor detection function, contact both the external environment and the central nervous system. The possibility that substances applied to the epithelium might reach the central nervous system was investigated by the intranasal application of peroxidase-conjugated wheat germ agglutinin (WGA-HRP). WGA-HRP was transported through olfactory receptor axons to the glomerulus of the olfactory bulb. Reaction product was localized electron microscopically to tubulovesicular profiles and dense bodies in sensory axons. Evidence of transneuronal transport was indicated by reaction product localized in dense bodies in dendrites postsynaptic to receptor cell axons. Periglomerular, tufted and mitral cells in the olfactory bulb also were transneuronally labeled. Anterograde transneuronal labeling occured in the olfactory tubercle, piriform cortex and surrounding the lateral olfactory tract. Retrograde transneuronal label was found in neurons of the basal forebrain with the largest number of perikarya in the lateral nucleus of the horizontal limb of the diagonal band, a major source of cholinergic afferents to the olfactory bulb. These data suggest that substances, specifically those which bind to receptors, are transported from the olfactory receptor neurons in the nasal epithelium to the brain. Thus, the olfactory system may provide a route of entry for exogenous substances to the basal forebrain.Abbreviations AC anterior commissure - CC corpus callosum - CI internal capsule - CP caudate putamen - DBB diagonal band of Broca - FX fornix - GP globus pallidus - IC island of Callelae - LV lateral ventricle - MS medial septum - OC optic chiasm - PIR piriform cortex - RF rhinal fissure - SON supraoptic nucleus - SCN suprachiasmatic nucleus - SM stria medullaris - ST stria terminalis - TOL lateral olfactory tract - TUO olfactory tubercle - III third ventricle