Rap1 is activated by cross-linking of CD44 with activating antibody. (A,B) RAW macrophages were treated or not with PMA at the indicated doses prior to phagocytosis of (A) CD44 Ebabs or (B) iC3b-coated prey. * indicates different from the nontreated cells (P < .05). Data are shown as the mean plus or minus SE; n = 6. (C) GST-RAL pull-down of activated Rap1 followed by Western analysis of RAW macrophages stimulated or not with PMA, isotype control, or anti-CD44 antibody (representative of 3 independent experiments), followed by densitometry analyses of anti-Rap1 Western blots using Image J 1.47 software. Data are expressed as the ratio of expression of Rap1 relative to nonstimulated control. * indicates different from CTRL isotype and PMA; ^ψdifferent from CTRL isotype and CD44 (P < .05). Data are shown as the mean plus or minus SE; n = 3.