In the present study, we found that SSc patients, who were not on immunosuppressive treatment, had significantly reduced numbers of lymphocytes and its subsets including CD3+, CD4+, CD8+, and CD19 cells. However, the percentages of lymphocyte subsets investigated were very similar to those observed in healthy controls. In accordance with our results, Ercole et al.  recently found that SSc patients had similar percentages of CD3+, CD4+, and CD8+ cells and CD4+/CD8+ cell ratio when compared to matched normal controls. Ingegnoli et al.  found that absolute counts of CD4+CD25+ and CD8+ lymphocytes are reduced in SSc patients. On the other hand, Artlett et al.  reported that the numbers of CD4+ and CD8+ cells were found to be significantly higher in SSc patients than in controls. However, Fiocco et al.  observed that patients with SSc showed increased CD4+CD26+ and CD4+CD25+ absolute numbers and percentages and decreased CD8+CD29+ percentages compared with controls.
Natural killer cells are large granular lymphocytes easily identified morphologically by the presence of azurophil granules in their cytoplasm and they commonly express certain cell surface markers such as CD56+ which is a homophilic adhesion molecule that belongs to the immunoglobulin superfamily. Natural killer cells mediate antigen presentation and secrete immune modulator cytokines like interferon, colony stimulating factor - these functions suggested the involvement of natural killer cells in the pathophysiology of SSc. Reduction of natural killer cells has been described by Riccieri et al. . Interestingly, Mitsuo et al.  observed that the frequency as well as the absolute number of CD161+CD8+ cells, which are closely related to CD8+ natural killer cells, were decreased in the peripheral blood of SSc patients.
Presence of autoantibodies and hypergammaglobulinaemia support the role of humoral immunity. CD19+ is a cell surface marker of B lymphocytes. We observed significantly reduced levels of CD19+ cells which inversely correlated with the clinical score of SSc patients. Sato et al.  found that CD19 is over-expressed in naive B cells and, to a greater extent, in memory B cells in the blood SSc patients. This CD19 overexpression was specific to SSc, since SLE patients exhibited significantly down-regulated CD19 expression. Sato et al.  suggested that the CD19 overexpression in SSc memory B cells induces both the activated phenotype of memory B cells and augmented IgG production. However, Majone et al.  recently reported on increased apoptosis in circulating lymphocyte cultures of anti-RNA polymerase III positive patients with SSc. Indeed, this might be a possible mechanism to explain the reduced lymphocyte counts in SSc patients.
In conclusion, the aforementioned data on lymphocyte subsets in SSc are conflicting very likely due to different methodologies particularly with regard to patient selection, pre-treatments, assays, and sample sizes. Although the relations between the lymphocyte subpopulations investigated was not different from healthy controls, we found a significant reduction of absolute numbers of lymphocytes and CD3+, CD4+, CD8+, and CD19+ cells SSc patients. Interestingly, the absolute number of CD19+ cells appears to inversely correlate with the severity of cutaneous involvement. Hence, the CD19 count may be a potential biomarker for the severity of skin involvement. Taken together, our data support previous reports indicating that subsets of T lymphocytes as well as B lymphocytes play a role in the pathogenesis of SSc.