IgE is present on peripheral blood monocytes and B cells in normal dogs and dogs with atopic dermatitis but there is no correlation with serum IgE concentrations.

Blood was collected from 29 dogs, 14 with atopic dermatitis (AD) and 15 controls. Total serum IgE was quantitated. Peripheral blood monocytes were harvested and labeled with leucocyte markers and anti-canine IgE before analysis by flow cytometry. There was no statistically significant difference between the atopic and control groups when the mean number of cells in the monocyte (CD14), antigen presenting cell (CD1c) or B cell (CD21) populations were examined. However, the variation in cell numbers was significant and much greater in the atopic group for CD1c and CD14 labeled cells. The mean percentage of double labeled cells, CD1c/IgE and CD14/IgE was significantly lower in the atopic population compared with the controls. More variation was observed in the numbers of monocytes of atopic dogs (CD14/IgE) and antigen presenting cells (CD1c/IgE) of control dogs. The mean percentage of B cells expressing IgE was 65 and 51% in the atopic and control groups respectively which is greater than that reported in humans. There was no statistically significant difference. Total serum IgE concentrations were similar in each group and did not correlate with cell bound IgE in any of the leucocyte populations studied. Canine AD is associated with more variability in circulating monocyte numbers and lower numbers of monocytes expressing IgE than control dogs. Unlike in humans, there is no correlation between circulating and cell bound IgE. Furthermore, high levels of IgE in the dog may be related to a greater number of B cells in the circulation committed to IgE production.