Expression of the human immunoglobulin heavy chain V(H)6 gene element by fetal B lymphocytes

Fetal B lymphocytes in mice and humans use a limited number of the available V-H gene segments. Mouse fetal B cells primarily utilize 3' V-H elements, suggesting that the localization of these elements determines their rearrangement frequency. The previously reported non-random usage of human V-H genes has been more difficult to explain. In this study the authors analysed the expression of the most proximal 3' human V-H element (V(H)6) using a monoclonal antibody (JE-6). V(H)6 expression was assessed in various B cell differentiation stages from fetal liver, bone marrow and spleen at 12-20 weeks of gestation. The authors demonstrate that the level of V(H)6 expression doss not exceed a stochastic usage frequency. This suggests that the localization of V(H)6 does not significantly promote its expression during human fetal life, and that other factors must affect the usage of V-H genes during human fetal development.