CSF/serum quotient graphs for the evaluation of intrathecal C(4 )synthesis

BACKGROUND: Cerebrospinal fluid (CSF)/serum quotient graphs have been used previously to determine local synthesis in brain of immunoglobulins and C(3 )complement component. The aim of this study was to use the same technique to construct quotient graphs, or Reibergrams, for the beta globulin C(4 )and to evaluate the method for assessing intrathecal synthesis in neurological disease. METHODS: The constants in the previously-defined Reibergram for immunoglobulin IgA were used to calculate the CSF/serum quotient for C(4). CSF and serum were analyzed for C(4), IgA and albumin from a total of 12 patients with meningoencephalitis caused by encapsulated microorganisms and 10 subjects without infections or inflammatory neurological disease, some of which had dysfunction of the blood-CSF barrier, RESULTS: The formula and C(4 )Reibergram with the constants previously found for IgA, determined the intrathecal C(4 )synthesis in CSF. The intrathecal C(4 )fraction in CSF (C(4 )loc in mg/l) was compared to the C(4)-Index (fraction of CSF: serum for C (4)/fraction of CSF: serum for albumin). There was a significant correlation between the two formulae. The CSF/Serum quotient graph was superior for detecting intrathecal synthesis of C(4 )under variable conditions of blood-CSF barrier permeability. CONCLUSION: The C(4 )Reibergram can be used to quantify the intrathecal synthesis of this component of the complement system in different infectious diseases of the central nervous system and is especially useful for patients with blood-brain barrier dysfunction.