SCAVENGER RECEPTORS MEDIATE ADHESION OF ACTIVATED B-LYMPHOCYTES

The scavenger receptor (SR-A) is considered to play a role in host def ense by scavenging endotoxins, oxidized proteins, and denatured or oth erwise modified self components, which are routed toward degradation i n macrophages. Recent data suggest that SR-A also functions as an adhe sion molecule. Our previous finding of SR-A expression by high endothe lial cells of venules and on follicular dendritic cells in peripheral lymph nodes prompted us to investigate whether SR-A can act as an addr essin for lymphocytes. We describe here that activated B cells adhere to CHO cells transfected with either the type I or type II isoform of SR-A. In contrast, resting B cells isolated from peripheral blood did not adhere to SR-A transfected CHO cells. Other types of leukocytes di d not bind to SR-A. The adhesive properties of B lymphocytes in differ ent stages of activation were further explored using lymphoma cell lin es of the B cell lineage. The in vitro EBV-transformed B cell line IAR C171 showed enhanced adhesiveness to SR-A, whereas the Burlritt lympho ma cell lines, BL41, Rael, and BL16 did not. The SR-A-dependent adhesi on of B lymphoblasts occurred both at 37 and 4 degrees C, suggesting t hat it was not dependent on cell metabolism. The known polyanionic lig ands for SR-A, fucoidan, and acetylated low density lipoprotein, which bind to a positively charged portion of the collagen-like domain of S R-A, did not inhibit adhesion. This finding suggests that SR-A mediate s adhesion of activated B lymphocytes through a binding site that diff ers from the one that binds polyanionic ligands. Together, our data su ggest that SR-A plays a role in the recruitment of activated B cells i nto lymph nodes and inflammatory lesions by acting as an adhesion mole cule for such cells. (C) 1998 Academic Press.