Fig. 4. CD44 and RHAMM/IHABP are not the HA receptors that mediate the synthesis of MMP-9 and MMP-13 induced by HA. (A) For a HA-binding assay, soluble FITC-labelled HA (HA-FITC) was added to 3LL cells. To determine whether HA binding is CD44-dependent, cells were preincubated with CD44-specific antibodies KM81 (left) or IM7 8.1 (right) before HA-FITC was added. As a negative control, cells were incubated with unlabelled HA (HA). (B) HA binding to CD44 was blocked in 3LL cells by incubation with KM81 antibody (IgG or F(ab')₂) for 45 minutes on ice. The cells were then seeded with or without 0.5 mg ml^-1 rooster comb HA and together with KM81 antibody IgG or F(ab')₂ (as appropriate). Mmp-9 expression was then analysed by RT-PCR. (C) Expression of Mmp-9 and Mmp-13 was determined by RT-PCR analysis in MEFs deficient for either CD44 or RHAMM/IHABP treated with or without rooster comb HA (1 mg ml^-1).