Interactions between the endocrine and immune systems have been described in terms of a variety of phenomena, occurring at different organismal levels, including the anterior pituitary (AP). Vankelecom et al. (1) previously ascribed a prominent role in immune-endocrine interaction to the folliculo-stellate (FS) cells, based on the production by FS cells of the cytokine interleukin-6 (IL-6). FS cells constitute a network of stellate-shaped non-hormone secreting cells within the AP (2). We previously demonstrated that FS cells, that are positive for the neuroectodermal marker S-100 (3,4), play a role in intercellular communication with hormone producing cells, generally resulting in the attenuation of secretory responses following stimulation of these cells (5,6). Otherwise, the S-100 protein has also been shown to be marker of dendritic Langerhans cells in the skin (7), and of the socalled interdigitating reticulum cell of the lymph node (8). We recently demonstrated in the normal pituitary of the mouse and the rat, a network of lymphoid dendritic cells (DC), positive for a lymphoid DC specific aminopeptidase in the mouse and expressing MHC class II determinants in both species (9).