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Antigen‐specific immunoglobulin E+ B cells are preferentially localized within germinal centres

Allergen‐specific immunoglobulin E (IgE) mediates immediate‐type hypersensitivity reactions and plays a central role in allergic diseases. Although antigen‐driven B‐cell maturation and isotype switching occur within germinal centres (GCs), the role of GCs in IgE production is poorly understood. In view of this, we investigated the development of IgE‐expressing cells within GCs in response to an extensively characterized antigen, 2‐phenyloxazolone (phOx). The phOx‐specific IgE‐expressing cells localized within GCs 7 days after immunization, and peaked in number on day 11. Surprisingly, very few IgE‐positive cells were found in the T‐cell areas of the lymph node. Flow cytometric studies confirmed that IgE was expressed by B cells and was not the result of trapping by follicular dendritic cells. The specificity of the antibody response was confirmed by microdissection and reverse transcription‐polymerase chain reaction using phOx‐specific IgE primers. IgE‐positive cells were primarily found within GCs while, in contrast, many IgG1‐positive cells could also be detected outside GCs in the T‐cell areas. Taken together, these data highlight the importance of GCs in the production of antigen‐specific IgE antibody.