Immunoglobulin-secreting cells in healthy peripheral blood mononuclear cells.

Immunoglobulin-secreting cells were measured in healthy uncultured peripheral blood mononuclear cells (PBMCs) in vitro. The percentage of IgM-, IgG- and IgA-secreting cells in adult PBMCs was 0.053, 0.099 and 0.065%, respectively. The percentage of IgM-, IgG- and IgA-secreting cells was 0.73, 5.2 and 3.8% of surface IgM-, IgG- and IgA-bearing cells, respectively. The numbers of IgM-, IgG- and IgA-secreting cells increased with age in childhood. However, the numbers of all three classes were slightly decreased in adults compared with children aged 9-15 years. These results may explain the difference in immunity in vivo.