Soluble HLA measurement in saliva and cerebrospinal fluid in Caucasian patients with multiple sclerosis: a preliminary study

Background: Measurement of soluble HLA in body fluids has a potential role in assessing disease activity in autoimmune disorders. Methods: We applied a solid phase, enzyme-linked immunoassay to measure soluble HLA class I (sHLA-I) and class II (sHLA-II) molecules in the saliva and cerebrospinal fluid (CSF) in 13 untreated patients with relapsing-remitting form of multiple sclerosis (MS). For comparison purposes, we also studied saliva from 53 healthy subjects. Results: Saliva from normal controls had detectable sHLA-I levels in 41 of 53 individuals studied, with values ranging from 9-100 ng/ml (mean = 41 +/- 2.8 ng/ml). sHLA-I was undetectable in the saliva in 11 of 13 MS patients, and in none of the CSF specimens. In contrast, mean sHLA-II concentration in the saliva of MS patients was significantly increased compared to controls (386 +/- 52 unit/ml vs. 222 +/- 18.4 unit/ml, t = 8.68, P < 0.005). The mean CSF sHLA-II level (369 +/- 16 unit/ml) was equivalent to the mean sHLA-II concentration measured in saliva (mean = 386 +/- 52 unit/ml) (P = 0.7). In patients with brain magnetic resonance imaging (MRI) enhancing lesions (n = 5), reflective of more active disease, CSF sHLA-II averaged 356 +/- 26 unit/ml compared to 380 +/- 51 in saliva. Similarly, in patients with non-enhancing lesions (n = 8), CSF sHLA-II averaged 377 +/- 18 unit/ml compared to 390 +/- 77 unit/ml in saliva. Thus, the mean sHLA-II concentration in saliva and CSF was essentially equivalent for MS patients with or without enhancing plaques. Conclusion: Our data suggest that the measurement of soluble HLA in saliva, specifically sHLA-II, correlates with the level found in the CSF. Therefore, if sHLA correlates with disease activity in MS, as has been proposed, saliva measurements provide a noninvasive correlate of CSF measurement.