Increased expression of CD40 ligand in activated CD4+ T lymphocytes of systemic sclerosis patients

CD40-CD154 interactions play a key role in regulating immune response and are involved in the development of some autoimmune diseases. We analysed the expression of CD154 antigen in CD3-activated PBMC from 10 systemic sclerosis (SSc) patients and 10 control subjects by immunofluorescence. PBMC from SSc patients showed an increased expression of this molecule, since, 6 h following CD3 stimulation, the percentage of CD154(+)cells was of 17. 53+/-2.0 (mean+/-SE) in control and 25.33+/-2.93 in patient cells (P0.03). The higher expression of CD154 antigen was ascribible to CD4(+)cells. The enhanced induction of CD154 following CD3 stimulation depended on protein synthesis, since was abolished when the cells were stimulated via CD3 in the presence of cycloheximide. By analysing the expression of the CD40-induced antigen CD80, we verified that a blocking anti-CD40 antibody inhibited CD80 appearance in SSc activated monocytes, indicating that CD154 molecule was functional. These results show an enhanced expression of a functional CD154 molecule in SSc CD4(+)activated T lymphocytes.