Chapter 22: Localization patterns for immunoglobulins and albumins in the brain suggest diverse mechanisms for their transport across the blood-brain barrier (BBB)

Publisher Summary The blood–brain barrier (BBB) differentially excludes serum γ-globulins and albumin. The mean concentration of immunogammaglobulin (IgG) in cerebrospinal fluid (CSF) of adult humans is about 8 times lower than albumin. In this chapter, immunostaining for IgG and albumin in rat brain sections is compared to determine any differences in the patterns of intracellular vs. extracellular staining. For most animals, selective staining for albumin was far more prevalent than for IgG. Although there were numerous other immunopositive areas, differences seen in staining in of the hippocampus, hypothalamus, and cortex are compared. Generally, patterns of staining included either dark or clear cells on a dark background, or dark cells on a clear background. In areas such as the lateral septum, there were clear (unstained) neurons on a dark background possibly because of diffusion of CSF-borne proteins into the neuropil, yet no uptake of the protein by lateral septa1 neurons. Similarly, neurons in superficial layers of the cerebral cortex were clear on a dark background of neuropil.