Previous studies showed the presence of glial fibrillary acidic protein (GFAP) in cells located at different blood—tissue interfaces (astrocytes, hepatic stellate cells, kidney glomeruli mesangial cells, alveolar fibroblasts), the blood-urine interface (podocytes), and air-body interface (skin keratinocytes and fibroblasts). Similar features of these cells hinted at the comparability of tasks at different metabolically active regions. In the present study performed with adult rat heart and spleen sections, anti-GFAP antibodies were immunoreacted with interstitial Cajal-like cells in close proximity to capillaries, between the striated muscles of the myocardium, and along the lumen of the ventricles. In spleen sections, anti-GFAP antibodies labeled cells associated with capillaries, follicular arteriole, central artery, and marginal sinuses separating two functionally different regions of the spleen: the white and red pulp. This study presents yet another example of the immunoreactivity of GFAP at the border of the blood-tissue interface that, again, supports our hypothesis concerning the importance of the GFAP cytoskeleton in intracellular functions associated with the exchange between metabolically different environments.