The self antigen heme evades immune recognition by sequestration in some hemoproteins

Heme is a non-protein autoantigen which is ubiquitous in vivo, primarily complexed in various hemoproteins or bound to specialized carrier molecules. Nevertheless, heme is able to stimulate a high frequency of CD4⁺, class II-restricted T cells, freshly explanted from unprimed mice, to proliferate in vitro. In this study, we show that heme incorporated into various species of mammalian cytochrome c (cyt c), including murine cyt c, represents a facultative cryptic determinant, able to be recalled only at high doses of native cyt c. By contrast, avian cyt c is of comparable antigenicity to free heme. Artificially denatured carboxymethylated (CM) mammalian cyt c exhibited greatly increased antigenicity, comparable to that of heme and avian cyt c, indicating that the crypticity of heme in native mammalian cyt c is due to the resistance of the native conformation of this molecule to antigen processing within murine antigen-presenting cells. Thus, tolerance to the heme group of at least some hemoproteins, may be maintained by the crypticity of the heme, rather than by deletion of hemereactive T cells. Given the high frequency of heme-reactive T cells in unprimed mice, these findings suggest that heme may become an important modulator during an inflammatory response.     

No Association between SNP rs498055 on Chromosome 10 and Late-Onset Alzheimer Disease in Multiple Datasets

SNP rs498055 in the predicted gene LOC439999 on chromosome 10 was recently identified as being strongly associated with late-onset Alzheimer disease (LOAD). This SNP falls within a chromosomal region that has engendered continued interest generated from both preliminary genetic linkage and candidate gene studies. To independently evaluate this interesting candidate SNP we examined four independent datasets, three family-based and one case-control. All the cases were late-onset AD Caucasian patients with minimum age at onset ≥ 60 years. None of the three family samples or the combined family-based dataset showed association in either allelic or genotypic family-based association tests at p < 0.05. Both original and OSA two-point LOD scores were calculated. However, there was no evidence indicating linkage no matter what covariates were applied (the highest LOD score was 0.82). The case-control dataset did not demonstrate any association between this SNP and AD (all p-values > 0.52). Our results do not confirm the previous association, but are consistent with a more recent negative association result that used family-based association tests to examine the effect of this SNP in two family datasets. Thus we conclude that rs498055 is not associated with an increased risk of LOAD.     

Plasticity of epidermal stem cells

The keratinocyte cell compartment in the continuously renewing epidermis of the skin is maintained by undifferentiated, self-renewing stem cells. We show that a small subpopulation of epidermal stem cells (EpiSCs) have the capacity to integrate into multiple tissues. These EpiSCs can change their phenotype in direct response of changes in cytokines in vitro, changes in cocultured cells, after injection into damaged environments in vivo. These changes appear to be unrelated to the age of the EpiSC. Even though we can isolate these cells and show that the age of thses cells appears to be irrelevant to this multipotent function, we still do not know how such cells are defined within a tissue or what the life span of a multipotent stem cell is.     

GABRD encoding a protein for extra- or peri-synaptic GABAA receptors is a susceptibility locus for generalized epilepsies

A major challenge in understanding complex idiopathic generalized epilepsies has been the characterization of their underlying molecular genetic basis. Here, we report that genetic variation within the GABRD gene, which encodes the GABAA receptor delta subunit, affects GABA current amplitude consistent with a model of polygenic susceptibility to epilepsy in humans. We have found a GABRD Glu177Ala variant which is heterozygously associated with generalized epilepsy with febrile seizures plus. We also report an Arg220His allele in GABRD which is present in the general population. Compared with wild-type receptors, alpha1beta2Sdelta GABAA receptors containing delta Glu177Ala or Arg220His have decreased GABAA receptor current amplitudes. As GABAA receptors mediate neuronal inhibition, the reduced receptor current associated with both variants is likely to be associated with increased neuronal excitability. Since delta subunit-containing receptors localize to extra- or peri-synaptic membranes and are thought to be involved in tonic inhibition, our results suggest that alteration of this process may contribute to the common generalized epilepsies.     

Taste preferences induced by trains of rewarding lateral hypothalamic stimulation of differing durations

The question of whether prolonged stimulation of the lateral hypothalamic area (LH) simply diminishes in rewarding effect or becomes aversive was tested in 32 rats using a taste preference technique. The animals were allowed to drink novel, coffee-flavoured water for 10 min, and then received 60 trains of LH stimulation with differing durations, at an intensity proven to be rewarding at 0.5 sec duration. In a test 24 hours later, those animals that had been stimulated with 1 or 5 sec trains showed a shift in preference from tap water to coffee water, but those stimulated with 10 sec trains did not. The results show that prolonged stimulation not only loses its positive reinforcement effect but becomes negative.     

Glomerular capillary morphology in normal humans

Knowledge of quantitative glomerular structure in normal man is limited. At the time of renal transplantation, 28 living-related normal kidney donors had renal biopsies performed. Tissue was processed for light and electron microscopy using standard techniques. Standard stereologic techniques were used to determine mean glomerular volume, capillary length density, fractional volumes of mesangium and capillary lumen, surface densities of the peripheral capillary, mesangial-epithelium interface, and the lumenal-mesangial interface. Volume of total mesangium/glomerulus, capillary lumenal volume/glomerulus, peripheral capillary filtration surface/glomerulus, capillary mesangial-epithelial surface/glomerulus, capillary lumenal-mesangial surface/glomerulus, capillary length/glomerulus, and average capillary diameter were calculated. There were no significant differences between males and females in any structural parameter. There were no significant correlations between age or body surface area and any structural parameter. In comparison with these normal values, previously reported diabetic patients with clinical nephropathy demonstrate markedly expanded mesangial volume/glomerulus and a diminished filtration surface/glomerulus. The availability of these normal values will allow comparison with functional data in normal humans and greater understanding of human glomerular disease.     

Factors influencing the sensitivity of herpes simplex virus detection in clinical specimens in a simultaneous enzyme-linked immunosorbent assay using monoclonal antibodies

A rapid simultaneous enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies was investigated for herpes simplex virus (HSV) detection. All HSV isolated (n = 127) were detected, whereas no response was obtained with HSV negative preparations. Equivalent results were obtained from 275 of 277 clinical specimens in the monoclonal ELISA and in an ELISA using polyclonal antibodies, confirming that appropriately selected monoclonal antibodies may be as efficacious as polyclonal antibodies in antibody-based assays. In clinical specimens, the rate of HSV detection (sensitivity) relative to tissue culture isolation was low for both assays, and the major factor responsible for this was the low concentration of virus present in some specimens. The sensitivity of ELISA obtained in routine use varied with different panels of unselected specimens and was related to the speed of development of the cytopathic effect. These results emphasise the need for caution in assigning a definitive sensitivity level to ELISA tests evaluated on different panels of specimens.     

Psychophysiological correlates of induced headaches

The psychophysiological correlates of induced headaches were examined. Subjects with frequent muscle-contraction headaches, frequent migraine headaches, or infrequent headaches were exposed to a 1-h cognitive stressor while multiple electromyographic and cardiovascular measures were monitored. The stressor was associated with significant changes in all psychophysiological measures. Eleven of 16 headache subjects and 2 of 8 control subjects developed headaches. Significant associations between several psychophysiological variables and headache occurrence were found and individual differences in the association between psychophysiological variables and headaches intensity were examined. The results were consistent with the hypothesized role of cardiovascular factors in the pathophysiology of muscle-contraction headache. This was the first controlled demonstration of headaches occurring as a function of environmental stressors.This research was supported by Grant 5-R01-NS-1875 from the National Institute of Health.