Elevated D8/17 expression on B lymphocytes, a marker of rheumatic fever, measured with flow cytometry in tic disorder patients

Objective: Elevated D8/17 expression on B lymphocytes is a known susceptibility marker of rheumatic fever. Previous studies have reported higher than usual D8/ 17 expression on B lymphocytes of patients with tic disorders. The purpose of this study was to assess D8/17 expression on B lymphocytes of tic disorder patients by using an objective method in which no operator variability was involved.

Method: D8/17 expression on B lymphocytes was assessed with flow cytometry by using an immunoglobulin M (IgM) monoclonal D8/17-specific antibody in an unselected group of Dutch patients with tic disorders (N=33) and healthy volunteers (N=20). Binding of this monoclonal antibody was compared with binding of an irrelevant IgM monoclonal antibody, and the shift in mean fluorescence intensity of the D8/17-specific antibody compared to that of the irrelevant IgM monoclonal antibody was used as a measure of D8/17 overexpression. For the patients, Yale Global Tic Severity Scale scores were used to assess disease severity.

Results: D8/17 overexpression in the patient group (mean=16.8 arbitrary units, SD=30.5) was significantly higher than in the comparison group (mean=3.2, SD= 3.0). A significant minority of the patients (N=13, 39.4%), however, had levels of D8/ 17 overexpression within the range of that of the healthy comparison subjects. Flow cytometric analysis did not indicate a separate subpopulation of D8/17-positive B cells.

Conclusions: These data confirm the utility of D8/17 B cell overexpression as a peripheral blood marker in patients with tic disorders and are compatible with a streptococcus-related pathogenesis for at least a subgroup of patients with tic disorders.