2003 Volume 66 Issue 4 Pages 327-335
The present study investigated the development of plasma cells in the early rat yolk sac (days 10-16 of gestation) by light microscopy, transmission electron microscopy, immunoelectron microscopy, and indirect immunofluoresce techniques. Cells delineating the morphology of plasma cells in the yolk sac were observed as early as 12 days of embryonic life. As for positive immune staining for the intra-cyto-plasmic immunoglobulin (Ig) production (IgA, IgM and IgG), the intensity of the immune staining was very weak on days 10 and 11 of gestation, while it turned very dense on day 12 of gestation. At 14 days of gestation, the number of positive cells was markedly reduced. Immunoelectron microscopy visualized products of the immune reaction in cisterns of the rough endoplasmic reticulum. Conventional electron microscopic examination of 12, 13, and 16-day yolk sacs confirmed the development and differentiation of plasma cells with their well-known ultrastructural features, making this the first study to demonstrate these in the early rat yolk sac. The development of plasma cells in the early yolk sac implies the ability of the yolk sac to effect a humoral immune response at this stage of fetal life. The probable role of plasma cells in the yolk sac is also discussed.
