IGHE and Allergy: Figure 2 shows that IgE-producing B-lymphocytes accounted for 0.23% of subpopulations of CD19+ cells after the birch pollen season (Figure 2, 6th June) and after one more month (Figure 2, 4th July) this subpopulation disappeared. This would suggest that IgE-producing cells appear in the peripheral blood after allergen exposure. In fact, they seem to be present in allergic patients with a perennial allergy (Figure 2, Year-around allergy) and are absent in a healthy non-allergic donor blood (Figure 2, Healthy donor).