Background
Recently, a study from the Consortium of Food Allergy Research (CoFAR) showed that allergen‐induced IL‐4 expression in CD25+ mononuclear cells was increased in allergic patients. However, they did not find the expected increase in GATA‐3 expression, suggesting that allergen‐induced IL‐4 might not be of T‐cell origin. We sought to determine whether other cell types were responsible for the increased IL‐4 expression in the CD25+ cell population.
Methods
Comparing six allergic patients and six healthy controls, we analyzed the CD25+ isolated population from PBMC for the presence of potential IL‐4‐expressing non‐T cells. We also compared spontaneous expression levels of surface markers (CD203c, CD63, CD25, and HLA‐DR) on basophils from whole blood of 42 peanut‐allergic patients and from 12 non‐atopic controls. Expression of these markers was also evaluated following basophil activation in eight peanut‐allergic patients selected from the previous cohort.
Results
In addition to CD4+ T cells, a substantial proportion of non‐T cells were found in the CD25+‐isolated cell population: basophils, NK, and NK‐T cells with a mean percentage ± s.e.m. of 5.24 ± 0.63%, 6.65 ± 1.01%, and 6.01 ± 1.04%, respectively. The majority of these cells exhibited positive intracytoplasmic staining for IL‐4. Expression of CD63 and CD25 was significantly higher in allergic patients compared with controls (p < 0.05). Interestingly, we found a significantly higher proportion of activated basophils expressing HLA‐DR, compared with non‐activated basophils (p < 0.05).
Conclusions
Our results support the suggested key role of non‐T cells secreting IL‐4 in food allergy, particularly basophils, which may also play a central role in antigen presentation.