Epitope specificity determines cross-protection of a SIT-induced IgG4 antibody.

BACKGROUND: The calcium-binding 2EF-hand protein Phl p 7 from timothy grass pollen is a highly cross-reactive pollen pan-allergen that can induce severe clinical symptoms in allergic patients. Recently, a human monoclonal Phl p 7-specific IgG4 antibody (mAb102.1F10) was isolated from a patient who had received grass pollen-specific immunotherapy (SIT). METHODS: We studied epitope specificity, cross-reactivity, affinity and cross-protection of mAb102.1F10 towards homologous calcium-binding pollen allergens. Sequence comparisons and molecular modelling studies were performed with ClustalW and SPADE, respectively. Surface plasmon resonance measurements were made with purified recombinant allergens. Binding and cross-reactivity of patients' IgE and mAb102.1F10 to calcium-binding allergens and peptides thereof were studied with quantitative RAST-based methods, in ELISA, basophil activation and IgE-facilitated allergen presentation experiments. RESULTS: Allergens from timothy grass (Phl p 7), alder (Aln g 4), birch (Bet v 4), turnip rape (Bra r 1), lamb's quarter (Che a 3) and olive (Ole e 3, Ole e 8) showed high sequence similarity and cross-reacted with allergic patients' IgE. mAb102.1F10 bound the C-terminal portion of Phl p 7 in a calcium-dependent manner. It cross-reacted with high affinity with Ole e 3, whereas binding and affinity to the other allergens were low. mAb102.1F10 showed limited cross-inhibition of patients' IgE binding and basophil activation. Sequence comparison and surface exposure calculations identified three amino acids likely to be responsible for limited cross-reactivity. CONCLUSIONS: Our results demonstrate that a small number of amino acid differences among cross-reactive allergens can reduce the affinity of binding by a SIT-induced IgG and thus limit cross-protection.

Source generators of mismatch negativity to multiple deviant stimulus types.

The purpose of the present study was to investigate auditory stimulus feature processing and how neural generators might differ among the mismatch negativity (MMN) responses to intensity, frequency, and duration deviant stimuli. Data collected from 72 electrodes in twelve adult female subjects were analyzed. For each subject, peak amplitude and latency values at Fz were compared among responses to the three deviant stimulus types presented in individual conditions with a probability of 0.10 and 0.30, and in the multiple deviant condition in which all three deviant types were presented (design based on Deacon et al. 1998). Further, equivalent current dipoles (ECD) for each deviant type, in each condition, and for each subject were calculated in three areas: right hemisphere, left hemisphere, and frontal. Peak amplitude and latency measured at Fz were consistent with previous findings by Deacon et al. (1998) and suggested parallel processing, perhaps by separate neural generators. However, ECD locations were not significantly different among the responses to the different deviant types. Further, the ECD magnitudes did not consistently reflect the differences in amplitude observed at the scalp among responses to the deviant types and conditions. The latter finding may indicate that the procedures were not sensitive enough to identify true differences among the generators. Alternatively, it was suggested that searching for separate neural generators at the cortical level may be too restrictive because the process may begin in subcortical areas, as indicated in animal models.

Expression of IL-4, Cepsilon RNA, and Iepsilon RNA in the nasal mucosa of patients with seasonal rhinitis: effect of topical corticosteroids.

BACKGROUND: Nasal allergen provocation has demonstrated that allergen-induced rhinitis is associated with an increase in local IL-4 mRNA and IgE heavy chain (Cepsilon) and IgE heavy chain promoter (Iepsilon) RNA and that pretreatment with topical glucocorticosteroids inhibits the increase in these transcripts. OBJECTIVE: This study was undertaken to determine whether observations made after acute allergen provocation can be extended to the case of chronic exposure experienced during the pollen season. METHODS: Biopsy specimens were obtained from the inferior turbinate of 33 pollen-sensitive subjects with allergic rhinitis before and during pollen season. Patients were randomized in a double-blind fashion and treated with either topical steroids (200 microg fluticasone propionate twice daily; n = 16) or matched placebo nasal spray (n = 17) before the pollen season. Alkaline phosphatase anti-alkaline phosphatase immunocytochemistry was used to identify B cells (CD20+), and in situ hybridization was used to detect IL-4, Cepsilon, and Iepsilon RNA+ cells. RESULTS: Baseline examination revealed IL-4 and Cepsilon RNA but virtually no Iepsilon RNA+ cells in the nasal mucosa. Analysis revealed a significant difference in the expression of Cepsilon and Iepsilon RNA+ cells (p < 0.001). Biopsy specimens taken after antigen exposure exhibited highly significant increases in placebo-treated (p < 0.001) but not steroid-treated patients. In both groups, the number of CD20+ cells was unchanged when preexposure and postexposure biopsy specimens were compared. CONCLUSIONS: These results show strong support for the hypothesis that IgE class switching occurs locally within the nasal mucosa of subjects with seasonal allergic rhinitis and that this response can be inhibited through strategies directed against local IgE production.

Interaural attenuation using insert earphones: electrocochleographic approach.

We measured the interaural attenuation for click stimuli using insert earphones. Electrocochleographic thresholds were determined when clicks were presented both ipsilaterally and contralaterally to the recording ear. The interaural attenuation was calculated as the difference between ipsilateral and contralateral thresholds. Results from normal listeners showed that crossover occurred. Results agree with previous investigators who used a different approach. Results confirm that one may need to mask the nontest ear in clinical evoked potential testing even though insert earphones are used. Several approaches to the question of when to mask are proposed.

Quantification technique for the middle latency response.

Few objective analysis techniques have been developed for, or applied to, the auditory evoked middle latency response (MLR). This report demonstrates the applicability of the Fsp statistical technique (Elberling and Don, 1984) to the MLR time domain. Subjects for this study were 10 normal hearing young adults. The stimuli were 60, 40, 20 dB nHL clicks and a NS control. Evoked responses were obtained as a series of 10,000 individual traces for each stimulus presentation and analyzed off line to determine the applicability of the Fsp technique. In addition, the effects of filtering and time window size were examined to determine the optimum collection characteristics for the Fsp analysis method. The results indicate that the Fsp technique is a viable tool for estimating signal-to-noise characteristics of the MLR. When using the Fsp technique with the MLR the high-pass filter should be set to 20 Hz so that a 50-msec time window can be used.

Using the derived auditory brain stem response to estimate traveling wave velocity.

An estimate of the traveling wave velocity (TWV) was evaluated in 18 young adults to determine the technique's applicability as a possible tool in evaluating Meniere's disease. This TWV estimation uses a derived auditory brain stem response procedure requiring high-intensity masking. The results indicate that on average, TWVs were similar to those obtained via psychophysical measures or electrocochleography. However, instances of undermasking, due to subjects' intolerance, resulted in a number of subjects exhibiting faster than expected TWVs.

Thalamic and extrathalamic connections of the dysgranular unresponsive zone in the grey squirrel (Sciurus carolinensis).

The connections of the cortical dysgranular "unresponsive zone" (UZ) (Sur et al.: J. Comp. Neurol. 179:425-450, '78) in the grey squirrel were studied with horseradish peroxidase and autoradiographic techniques. The results of these experiments show that the major subcortical connections of the unresponsive zone are in large part reciprocal. Connections are distributed within the thalamus in a poorly defined region including restricted portions of several nuclei that lie along the rostral, dorsal, and caudal borders of the ventral posterior nucleus. Additional thalamic connections of the UZ terminate in the reticular nucleus and are reciprocally related to the paralaminar and central median nuclei. Extrathalamic terminations were observed in the zona incerta, the intermediate and deep layers of the superior colliculus, the red nucleus, and several subdivisions of the pontine nuclei. The similarity between the pattern of subcortical connections of the UZ in the grey squirrel and patterns reported for the parietal septal region in rats (Chapin and Lin: J. Comp. Neurol. 229:199-213, '84) and for area 3a in primates (Friedman and Jones: J. Neurophysiol. 45:59-85, '81), suggests that the UZ in the grey squirrel may represent a counterpart of at least part of area 3a as described in primates. The results are further discussed with respect to a possible role of the thalamus in control or modulation of interhemispheric circuits and of the UZ in the modulation of nociceptive and kinesthetic pathways through the thalamus. Finally, the term parietal dysgranular cortex (PDC) is proposed as an alternative to denote the region currently called the unresponsive zone.