Identification of sympathetic neuroblasts and chromaffin cells in human fetal adrenal glands by immunohistochemical analysis. Sections of a human fetal (19 weeks) adrenal gland, adjacent to those used for laser capture retrieval of cells for mRNA extraction and gene expression profiling, were stained with (a) hematoxylin and eosin or antibodies directed against (b,f) TH, (c,g) CHGA, (d,h) BCL2, and (e,i) HNK1. Whereas the immunoreactivities of BCL2 and HNK1 are specific for neuroblasts, TH and CHGA expression is pronounced in chromaffin cells and weak in neuroblasts . Stars indicate chromaffin cells (TH+, CHGA+, BCL2-, and HNK1-), either solitary or intermingled with neuroblasts. Panels a-e show a cluster of adrenal neuroblasts and panels f-i show cortical area within scattered chromaffin cells adjacent to the neuroblast cluster. Inserts in panels b-e (bars: 10 μm) correspond to the boxed areas in these panels (bars in panels a-i: 100 μm). BCL2, B-cell CLL/lymphoma 2; CHGA, chromogranin A; H&E, hematoxylin and eosin; HNK1, carbohydrate epitope; TH, tyrosine hydroxylase.