PROPERTIES OF HUMAN FOLLICULAR DENDRITIC CELLS PURIFIED WITH HJ2, A NEW MONOCLONAL-ANTIBODY

Follicular dendritic cells (FDC) are found in germinal centers and may play an important role in germinal center (GC)B cell development. How ever, very little is known about FDC because it is very difficult to o btain a pure preparation of FDC. To aid in the purification of human F DC, we produced a mouse monoclonal antibody named HJ2 that immunohisto chemically stains FDC in various lymphoid tissues. Isolated HJ2(+) cel ls obtained by flow cytometric cell sorting exhibit morphological feat ures associated with FDC and display numerous FDC-associated surface m arkers, but do not express T cell and B cell markers. Taken together, these findings indicate that HJ2 binds FDC and can be used to purify h uman FDC. Phenotypic studies of purified FDC revealed that FDC express large amounts of the complement (C)-regulatory proteins CD46, CD55, a nd CD59. By deactivating C, these proteins may safeguard FDC from memb ranolysis by surface-bound C containing immune complexes. To begin stu dies of FDC function, we cultured purified FDC and found they survive for at least 2 weeks in vitro. Furthermore, FDC were potent stimulator s of allogeneic peripheral blood mononuclear cells and a T cell line i n mixed lymphocyte cultures, and on a cell basis, FDC were more active than B cells. The purification of functionally active human FDC shoul d facilitate studying the role of FDC in B cell development within GC. (C) 1994 Academic Press, Inc.