There was a significant amount of non-specific, but not of allergen (e.g., papain, mite feces and four kinds of pollen)-specific, IgE antibodies (Abs) in the sera of normal mice. An i.n. injection of each allergen without adjuvant into mice caused an increase in total IgE Ab titers with a similar time course in the serum. However, the stage of initiation of allergy varied from allergen to allergen. Submandibular lymph node cells from normal mice contained papain-, but not mite feces- or pollen-specific IgE+ cells and an i.n. injection of papain induced papain-specific IgE Abs in the serum. In contrast, one (i.n.) or two (i.n. and s.c) injections of mite feces induced neither mite feces-specific IgE+ cells in the lymph nodes nor mite feces-specific IgE Abs in the serum. I.n. sensitization with cedar pollen induced cedar pollen-specific IgE+ small B cells in the lymph nodes on Day 10, when non-specific IgE Ab titers reached a peak in the serum, implying induction of related allergen-specific IgE+ small cells as well. In fact, a second (s.c.) injection of ragweed (or cedar) pollen into mice sensitized i.n. once with cedar (or ragweed) pollen, but not with mite feces, induced a large amount of ragweed (or cedar) pollen-specific IgE Abs in the serum. These results indicate that when firstly-sensitized non-specific IgE+ small B cells in mouse lymph nodes include some secondly-sensitized allergen-specific ones, mice produce IgE Abs specific for the secondly-injected allergen.
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