CD44-STIMULATED DENDRITE FORMATION (SPREADING) IN ACTIVATED B-CELLS

A rat monoclonal antibody (mAb) (NIM-R8), insolubilized by binding to plastic plates, induced a rapid and extensive formation of dendrite pr ocesses ('spreading') in B lymphocytes activated by anti-IgM and inter leukin-4 (IL-4) or anti-CD38 and IL-4. In contrast, resting B cells we re unable to spread similarly on the NIM-Rs-coated plates. The NIM-R8 antibody recognized a 90 000 MW surface glycoprotein (gp90) present on both B and T lymphocytes. The expression of this molecule was greatly increased after polyclonal (lipopolysaccarhide, anti-IgM plus IL-4 or concanavalin A) activation. The NIM-R8 mAb with or without IL-2 or IL -4 was unable to induce proliferation of splenic lymphocytes. Followin g the demonstration that the NIM-R8 mAb recognizes the murine equivale nt of human CD44, the induction of spreading of activated B lymphocyte s was studied using a panel of mAb recognizing different epitopes of m urine CD44. All of these different mAb induced similar spreading of ac tivated B cells. The ligand-inducible spreading of activated B lymphoc ytes may be an important mechanism for providing an increased cell-sur face area for cell-cell or cell-matrix interactions, and thus may be a n important factor controlling the response of activated lymphocytes.