Timing of onset of allergic symptoms as a response to a double-blind, placebo-controlled food challenge in patients with food allergy combined with a radioallergosorbent test and the evaluation of proliferative lymphocyte responses

Dose-response in double-blind, placebo-controlled oral food challenges in children with atopic dermatitis

BACKGROUND

Double-blind, placebo-controlled oral food challenges (DBPCFCs) are considered the "gold standard" for diagnosing food hypersensitivity, but the dose that elicits positive challenges, or determinants that may predict dose-response relationships, have not been reported.

OBJECTIVE

Our purpose was to determine the quantity of food that elicits reactions during DBPCFCs and to evaluate parameters that may predict the provocative dose and severity of reaction.

METHODS

We reviewed challenge data for all positive challenges to 6 common allergenic foods in children with atopic dermatitis evaluated for food allergy over a 13-year period. Challenge food was generally administered in 6 doses at 10- to 15-minute intervals beginning with 400 to 500 mg and completing with a total of 8 to 10 g of food. An open feeding of a larger portion followed negative challenges. At the physician's discretion, a lower starting dose was occasionally used (100 mg, 250 mg). Food-specific IgE antibody concentrations (radioallergosorbent test [RAST]) were determined on stored sera of 20% of the challenges selected randomly and 99.6% had prick skin tests (PSTs) performed to the challenged food.

RESULTS

A total of 196 children (45% male; median age 5 y 9 mo; atopic dermatitis 98%, asthma 62%) had 513 positive challenges distributed as follows: egg 267, milk 117, soy 53, wheat 40, peanut 24, fish 12. The percentage of children reacting at the first dose (500 mg or less) was as follows: egg 49%, milk 55%, soy 28%, wheat 25%, peanut 26%, and fish 17%. Twenty-six milk challenges and 22 egg challenges were positive at a first dose of 250 mg; 3 milk challenges and 7 egg challenges were positive at a first dose of 100 mg. Eleven percent of the reactions that occurred on the first dose were severe. The percentage reacting after the final dose of the DBPCFC (or during open challenge) were egg 11%, milk 12%, soy 19%, wheat 12.5%, peanut 8.7%, and fish 25%. There was not a strong correlation between PST absolute wheal size or score (adjusted for histamine controls) and dose at reaction or severity of reaction (R(s) range -0.22 to 0.39 for particular foods). Serum concentration of food-specific IgE did not correlate well with the dose causing a reaction or with severity (R(s) range -0.40 to 0.55 for particular foods).

CONCLUSIONS

This food-allergic population may react to as little as 100 mg of food, possibly less, and the dose causing a reaction and the severity of reaction is not predicted by PST or RAST. Lower doses (100 mg or less) should be investigated for their appropriateness in initiating DBPCFCs.

Peanut allergic subjects' peripheral blood mononuclear cell proliferative responses to crude peanut protein

BACKGROUND

Peanut allergy is characterized by a high frequency of severe and occasionally fatal reactions.

OBJECTIVE

To determine if there are features of the in vitro cellular response that may account for the observed severity of peanut allergy.

METHODS

Skin-prick testing (SPT), RAST assay of serum peanut-specific and total IgE and mixed peripheral blood mononuclear cells (PBMC) proliferative responses to crude peanut protein were measured in 44 peanut allergics with varying severity of clinical reactions. PBMC responses of 13 non-peanut allergic controls (six atopic) were also studied.

RESULTS

Subjects' PBMCs proliferated more than controls', even without stimulation. Subjects' PBMC proliferative responses did not correlate with clinical severity, SPT weal size or peanut-specific IgE levels. Controls' PBMCs did not respond to peanut. There was no correlation between PBMC response and time since last reaction to peanut. Subjects' PBMCs responded more than controls, to mitogen as well as allergen. Proliferation increased with increasing concentration of peanut protein (P < 0.0001).

CONCLUSION

PBMCs of peanut allergics demonstrate a dose-dependent response to peanut which does not correlate with clinical severity, SPT reaction or levels of peanut specific IgE. The response is antigen-specific. Peanut protein is not mitogenic and is not acting as a superantigen. While there are non-specific differences in the PBMC responses of peanut allergic individuals compared with atopic and non-atopic controls, these differences do not explain the unique severity of peanut allergy.

Interferon-gamma and interleukin-4 production of ovalbumin-stimulated lymphocytes in egg-sensitive children

BACKGROUND

The causal relation between egg allergy and cytokines derived from lymphocytes is unknown.

OBJECTIVE

Interferon-gamma (IFN-gamma) and interleukin-4 (IL-4) production of ovalbumin-stimulated and interleukin-2 (IL-2)-stimulated peripheral blood mononuclear cells from egg-sensitive patients was investigated and compared with that of stimulated peripheral blood mononuclear cells from nonatopic healthy children.

METHODS

Peripheral blood mononuclear cells from egg-sensitive patients and nonatopic healthy children were cultured with ovalbumin and IL-2 for seven days. The IFN-gamma and IL-4 concentrations in culture supernatants of the peripheral blood mononuclear cells were investigated.

RESULTS

The levels of IFN-gamma production of only IL-2-stimulated or both ovalbumin-stimulated and IL-2-stimulated peripheral blood mononuclear cells from egg-sensitive patients with atopic dermatitis was significantly higher than that of healthy children and that of egg-sensitive patients with immediate allergic symptoms.

CONCLUSIONS

Increased IFN-gamma production by lymphocytes after IL-2 and antigen stimulation has important implications for the mechanism of food-sensitive atopic dermatitis.

Intestinal inflammation in children with atopic eczema: faecal eosinophil cationic protein and tumour necrosis factor-alpha as non-invasive indicators of food allergy

BACKGROUND

Food allergy is contemplated in atopic eczema. Early recognition of food allergies is difficult and the diagnosis is often missed because of the non-specificity of symptoms. New non-invasive tests are clearly needed.

OBJECTIVE AND METHODS

We measured the concentrations of tumour necrosis factor-alpha, eosinophil cationic protein and alpha-1 antitrypsin in faeces as indicators of intestinal inflammation induced by double-blind placebo-controlled oral cow's milk challenge in infants and young children with atopic eczema.

RESULTS

An increased alpha-1 antitrypsin concentration (> 2 mg/g) after cow's milk challenge was detected in 43% of the infants positive as compared with 11% of the infants negative to challenge, P = 0.02. The concentration of eosinophil cationic protein in faeces increased after cow's milk challenge in patients positive to challenge (P = 0.02) but not in those negative to challenge (P = 0.79). The concentration of eosinophil cationic protein was enhanced particularly in patients manifesting immediate-type reactions to the cow's milk challenge. The concentration of tumour necrosis factor-alpha increased after cow's milk challenge in patients positive to challenge (P = 0.005) but not in those negative to challenge (P = 0.25). The concentration of tumour necrosis factor-alpha in faeces was enhanced particularly in patients manifesting delayed-type reactions to the cow's milk challenge.

CONCLUSION

We conclude that in children with atopic eczema food allergy is associated with intestinal inflammation indicating that more general immunologic disturbances than previously thought take place in these patients. We further suggest that faecal eosinophil cationic protein, tumour necrosis factor-alpha and alpha-1 antitrypsin distinctly indicate various reaction types of food allergy. Parallel testing with eosinophil cationic protein and tumour necrosis factor-alpha may significantly enhance the accuracy in diagnosis of food allergy in patients with atopic eczema.