Spleen: Histomorphological Changes of the White Pulp during Fetal Development

For a long time spleen has been an important field of study for researchers. However, details about changes of microscopic structure in spleen during the fetal period are far less available in literature. Our goals were to determine distribution of white pulp as well as its relationship with blood vessels and to observe development and distribution of blood vessels and arrangement of CD4+ and CD8+ lymphocytes. The study was carried out on 16 specimens of fetal spleens. After standard histological hematoxylin and eosin (H&E) staining, the specimens were stained with immunohistochemical methods. Antibodies for CD4+, CD8+ and vascular endothelial cells were used. Qualitative, semi-quantitative and quantitative analyses were performed. The results were statistically analyzed and graphically presented. By the 19th week of gestation lymphocytes can be found in spleen. The 24th week of gestation is the period of the formation of a white pulp of the spleen with centrally placed blood vessels in the follicles. Also, during this week the arterioles were completely surrounded by the CD4+ lymphocytes. The number of arterioles in spleen increases during fetal development. With the increase of gestational age of the fetus, lymphatic tissue in the parenchyma of the spleen increases, as well as the number of the arterioles, while the number of capillary blood vessels decreases.