Variation of barrier permeability for albumin and immunoglobulin G influx into cerebrospinal fluid.

BACKGROUND The aim of the present study was to analyze variations in permeability of albumin and immunoglobulin G (IgG) influx into cerebrospinal fluid (CSF) in a clinical setting. METHODS In a retrospective intra-individual comparison of CSF samples, we used the IgGIndex and its constituents to indicate alterations in IgG/albumin permeability. RESULTS We found altered IgGIndices in 25/64 patients (range -25% to +44%), with differently altered QAlb and QIgG values (-69% to +549%), unaltered IgG-Indices in a further 25/64 patients with equally altered QAlb and QIgG values (-46% to +107%), and no parameter alteration in 14/64 patients. Parameter alterations in 25/64 patients indicated that permeability of albumin was changed to different extents than for IgG. It changed in the same direction in 20/25 patients, and the opposite in five patients. In further 25/64 patients, equal QAlb and QIgG alterations indicated equally altered permeabilities and/or altered efflux of the proteins. In 14/64 patients, no alteration in permeability or efflux was seen. CONCLUSIONS Results revealed surprisingly variable intra-individual changes in permeabilities for albumin and IgG in pathologic as well as normal CSF. Differing changes in permeability indicate that the diffusion paths of the two proteins may react to disturbances independently of each other. The details of the influx permeability for albumin and IgG into CSF illustrate the prospect of a more comprehensive insight into the protein exchange between blood and CSF.