Lymphocyte subsets and CD45RA positive T-cells in normal canine cerebrospinal fluid

In order to evaluate changes in lymphocyte subpopulations of cerebrospinal fluid (CSF) cells in neurological diseases, normal control data have to be established. In this study we evaluated CSF samples from 65 dogs of both sexes and various breeds with an age range between 5 months and 6 years, and 20 one-year-old healthy inbred Beagles. For comparison, blood samples from 10 healthy dogs were examined. 14 different antibodies against leukocyte surface markers were used. The subpopulations were evaluated using flow cytometry (FACS) and immunocytochemistry. It could be shown that lymphocyte populations in CSF differ from peripheral blood in a few subsets. A relatively high degree of individual variation was found, not only in dogs of different breeds and ages, but also in the inbred Beagle population. These large individual variations suggest that repeated paired CSF-blood samples during the course of neurological disease should be examined within the same individual to obtain meaningful results. CD3+ and CD4+ T-cells were significantly lower in normal CSF. Of great interest is the fact, that T-cells, characterized by double staining CD3/CD45RA are present in variable numbers in normal CSF. In other species they are known to be naive or resting T-cells. CD4/CD45RA positive cells seem to be an important subpopulation of these CD45RA positive T-cells. Furthermore, by far more CD11b positive lymphocytes were observed in the CSF than in the peripheral blood and these are not large granular lymphocytes. The present study shows that systematic FACS analysis of CSF is feasible in larger animals such as dogs.