OBJECTIVES

Isoelectric focusing (IEF) is a laboratory technique that allows to separate proteic molecules based on their isoelectric point. This technique, applied to cerebro spinal fluid (CSF) IgG, has been used to study human neurological diseases. CSF IgG concentration increases either with neurological diseases that alter the blood-brain barrier (BBB), increasing IgG access from the blood, or with neurological diseases that determine local activation of the immune system with intrathecal synthesis (IS) of IgG. To date, no studies on IEF of canine CSF have been performed. The purpose of this study was to investigate IgG patterns of distribution in CSF of dogs with several neurological diseases and to compare these data to CSF total protein concentrations for each dog.

MATERIALS

Twenty-four dogs have been included in the study. Sixteen dogs had spinal cord compression (SCC), 3 dogs had brain neoplasia (BN), 2 dogs had cerebellar abiotrophy (CA), 1 dog had steroid-responsive meningitis (SRM), 1 dog had viral meningoencephalitis (VM), and 1 dog had probable degenerative myelopathy (DM). CSF has been collected from the cerebellomedullary cistern (22 dogs) and/or from the lumbar subarachnoid space (5 dogs). Immediately after collecting CSF, a blood sample has been taken from each dog. CSF total protein have been evaluated in all dogs. IEF has been performed on an agarose gel layer on 3.5 ul of unconcentrated CSF and 3.5 ul of diluted serum (1/380) of all dogs. At the end of the migration the molecules have been transferred on nitrocellulose membrane.

RESULTS

Two main types of distribution of IgG profile were found: the former mirrored the serum protein distribution, the latter was characterised by IgG bands of intrathecal synthesis (BIS). Of 16 dogs with SCC, 4 dogs had normal CSF and 12 dogs showed mild to moderate increase in CSF protein and IgG bands of hematic derivation (BsHD). The CSFs of the 3 dogs with BN had a mild to remarkable increase in protein content and only IgG BsHD. The CSFs of the 2 dogs with CA had normal protein content and no bands on IEF. The CSF of the dog with SRM had a remarkable increase in protein content and IgG BsHD. The dog with VM had CSF with remarkably increased protein content and one IgG BIS. The CSF of the dog with probable DM had a mild increase in protein content and one IgG BIS.

CONCLUSION

CSF protein content increases with several CNS diseases, however this parameter does not allow to discriminate between increased permeability of the BBB and IS of IgG. On the contrary, IEF allows to detect IgG BIS. No BIS were found on IEF of CSFs of dogs with SCC, BN, and CA. IEF of the CSFs of the dogs with probable DM and with VM showed one IgG BIS each. These findings are consistent with the pathogenesis of these diseases. IEF of the CSF of the dog with SRM showed no BIS. This finding is not in accordance with previous published data on this disease. A generalized polyclonal response of B lymphocytes might explain this discrepancy. Further research on IEF of dogs' CSF is needed to better characterize total protein and IgG patterns for most diseases of CNS.