Elevated in vivo expression of the costimulatory molecule B7-BB1 (CD80) on antigen presenting cells from a patient with SLE.

The CD28/CTLA4-B7-family plays an important role in T-cell costimulation and is crucial for IL-2 production and tolerance induction. The costimulatory molecule B7-BB1 (CD80) is expressed on activated antigen presenting cells, but its expression on peripheral blood mononuclear cells is very low. Here we report a patient with untreated SLE whose peripheral blood antigen presenting cells expressed increased amounts of B7-BB1.