An immunohistochemical study on foetuses and newborns lymph nodes with emphasis on follicular dendritic reticulum cells

Lymph nodes were withdrawn from twenty foetuses and eighteen newborns. Paraffin embedded tissues were stained by current histochemical methods and immunohistochemically processed with a panel of antibodies against dendritic reticulum cells (DRC) (CD21, CD35), endothelial cells (QBEnd/10-CD34, CD31, Factor VIII RAg), B lymphoid cells (L26, MB2), T lymphoid cells (UCHL1, DFT1, OPD4), monocytic cells (PGM1, KP1) and interdigitating dendritic cells (S100 protein, PGM1). The immunohistochemistry was focused on determining the initial appearance of DRC whose origin is still debated. They are currently considered to be transformed mesenchymal cells. This study shows that DRC make their appearance in the superficial or subcutaneous lymph nodes just at the beginning of extrauterine life whereas they are identifiable in the mesenteric lymph-nodes already during the foetal life. They acting as an enhancing microenvironment, appear to be related to B lymphocyte expansion. Their derivation from endothelial cells rather than other mesenchymal cells seems more probable.