Ontogenesis and differentiation of IgE B lymphocytes in the rat

In fetal liver, the stem cells of the B lineage transform into pre-B cells with intracytoplasmic mu-chains and thereafter into mature B cells with IgMc and IgMm. The other immunoglobulin classes appear later. The IgEm B cells appear on the day of birth. They bear IgMm and IgDm. Anti-IgM or anti-IgD suppression, performed from birth, prevents IgE synthesis. IgM and IgD seem to be necessary to IgE lymphocyte differentiation. Neonatal anti-IgE suppression seems to have no influence on IgE lymphocytes, but this result has to be confirmed. IgE immune responses are T-dependent. Neonatally thymectomized animals or rnu/rnu rats are unable to produce IgE immune responses. Axenic rats possess a great number of IgEm-IgAm-bearing cells in Peyer's patches; this is not observed in conventional animals. Nevertheless, the major problems are due to cells with receptors for IgE which must be differentiated from cells with intrinsic IgE. Work is under way to solve these problems.