COV-HD and COV groups were comparable in their WBCs total and differential counts, CD4+ T cells, and T regulatory cells, however, there was a significantly higher CD39 expression on T regulatory cells in COV-HD patients than in COV patients [0.006 cell/ μl (0–5.6) versus 0.002 (0–0.14), P 0.04]. The gene discussed is ENTPD1; the disease is Huntington disease.