Immunoglobulin-secreting cells in cord blood: Effects of Epstein-Barr virus and interleukin-4

The contribution of cord blood B lymphocytes to the immune response has bee n under considerable investigation. Cord blood B cells produce almost no an tibodies except of the immunoglobulin (Ig)M isotype, indicating immaturity of the cells or the environment they reside in. The aim of this study was t o investigate the number of circulating IgA-, IgM-, IgG-, and IgE-producing cells in cord blood in comparison to adult peripheral blood using the ELIS POT method. Moreover, we studied the effect of transformation with the Epst ein-Barr virus (EBV) on the proportion of cells producing different isotype s with or without interleukin (IL)-4. Cord blood had IgM-producing cells ci rculating predominantly, but also some IgA- and IgG-producing cells, wherea s adult peripheral blood contained high amounts of circulating IgA-producin g cells and some IgM- and IgG-producing cells. No circulating IgE-producing cells were found in either group. Transformation by EBV caused significant expansion of IgA-, IgM-, and IgG-producing cells in adult peripheral blood , but almost only of IgM-producing cells in cord blood. A low but detectabl e expansion of IgA- and IgG-producing cells was found. Cells producing IgE were still not found, even after EBV transformation. However, EBV transform ation in the presence of IL-4 increased the numbers of IgE-producing cells significantly both in cord blood and adult peripheral blood. These findings indicate that cord blood contains some circulating IgA- and IgG-producing cells that are expanded to some extent after EBV infection. They also indic ate that cord blood B cells have a similar capacity for IgE production to a dult peripheral blood B cells when appropriately stimulated.