17 beta-estradiol expands IgA-Producing b cells in mice deficient for the mu chain

Oestrogen is not only a sex hormone but also an important regulator of the immune system. Expression of the heavy chain of IgM (mu) is essential for B-cell differentiation. However, a small number of IgA-positive B cells can be found in mice lacking the mu chain (mu MT-/-). The aim of this study was to investigate the effects of oestrogen on this alternative B-cell pathway in mu MT-/- mice. Our results clearly demonstrate that oestrogen increases the frequency of IgA-producing B cells in mu MT-/- mice in both bone marrow and spleen cells. We also show that mature IgM-producing B cells are not required for oestrogen-mediated suppression of granulocyte-mediated inflammation or thymic involution. In conclusion, we demonstrate that 17 beta-estradiol benzoate increases the frequency of IgA-producing B cells in mu MT-/- mice, suggesting that oestrogen can influence the alternative B-cell pathway found in mu MT-/- mice.