CD244 Expression by Lymphocytes in Rheumatoid Arthritis With Concomitant Hepatitis C Infection

We aimed to assess the populations of lymphocytes: NK cells, NKT cells and T cells, and the expression of the immunoregulatory receptor CD244 (2B4) by each population in rheumatoid arthritis (RA) patients with concomitant hepatitis C virus (HCV) infection.

Lymphocyte phenotyping for NK cells (CD3-CD56+), NKT cells (CD3 + CD56+), and T cells (CD3 + CD56-) was analyzed by flow cytometry in patients with HCV positive RA (n = 21), HCV negative RA (n = 20) and controls (n = 11). Surface expression of CD244 by each lymphocyte population was quantified as mean fluorescence intensity and frequency of CD244 expressing cells.

Patients with and without concomitant HCV displayed comparable numbers of NK, NKT, and T cells to controls. We observed that the expression intensity of CD244 was downregulated by the lymphocyte populations in HCV positive and HCV negative RA compared to controls (NK CD244 p < 0.001, NKT CD244 p = 0.047, T CD244 p < 0.001). Yet, the downregulation was more profound in HCV positive RA, as CD244 expression by NK cells and T cells was decreased in HCV positive in relation to negative RA (p < 0.001 and p = 0.003, respectively). In addition, the frequency of CD244-expressing NK and NKT cells in HCV positive RA was lower compared to HCV negative RA and controls (p < 0.001 and p = 0.001, respectively). T cell CD244 expression was significant for discriminating clinically active from less active RA with and without HCV (n = 41), area under the curve = 0.717 (95% CI 0.560-0.873, p = 0.007).

Our findings reveal a distinct expression pattern of CD244 by lymphocytes of RA with HCV infection.