Immunohistological analysis of human fetal lymph nodes.

A panel of monoclonal antibodies directed against various lymphoid and non-lymphoid cell subsets was used to study the lymph nodes of human fetuses of 16-40 weeks. B cells were of intermediate size and were present at all ages in primitive follicles and in the outer cortex. The fetal B-cell immunophenotype is indicative of an intermediate stage of development, just preceding the differentiation to mature B cell. Forty to sixty per cent Leu1+ B cells were observed in the follicles until the end of the second trimester. At all stages, T cells showed an immunophenotype similar to type III thymocytes, different from adult peripheral T cells, with a marked predominance of CD4+ T cells. Leu7+ NK cells were generally absent. OKIa+ interdigitating reticulum cells were present in T-cell areas. Some axillary lymph nodes showed strongly CD1+ dendritic cells, probably Langerhans' cells. Macrophages and granulocytes were present in varying numbers. Altogether, our results indicate that fetal lymph nodes are quite well differentiated at an early fetal age, although T and B cells do not (yet) show adult immunophenotypes. The expression of the CD38 antigen may be a main marker related to the immaturity of fetal T and B cells.