Effects of serum amyloid P component on human lymphocytes

The P component of amyloid is a normal serum protein designated SAP. SAP has substantial homology with C-reactive protein (CRP). Recent studies have established the structure, tissue distribution and binding reactivities of SAP; however, as yet, very minimal insight into its function has been achieved. Recent studies, though somewhat controversial, have suggested a regulatory role for CRP on the immune response. In view of these studies, we wanted to evaluate the in vitro effects of SAP on several immunological properties of human lymphocytes. We found that SAP had a marked inhibitory effect on the proliferative response of lymphocytes to a variety of T-dependent mitogens. In addition, SAP markedly enhanced the formation of active E rosettes, a marker of activated T cells.