Reactivity of novel monoclonal antibodies to human laminin α4 chain. ELISA (A), Western blotting under reducing (B) and nonreducing (C) conditions, and immunoprecipitation (D). In ELISA, human serum albumin (HSA), recombinant human laminin-8 (rhLN-8, α4β1γ1), and recombinant human laminin-10 (rhLN-10, α5β1γ1) were coated on plastic, and mIgG and mAb 4C7 to human laminin α5 were used as controls. Seven mAbs (3D7, 3H2, 5D8, 6A12, 6C3, 8C10, and 9B2) were classified as specific for LNα4 chain. In Western blotting, antibody reactivity against LN-8–containing platelet lysate (B) and purified platelet LN-8 (C) are shown. mAbs DG10 (LNβ1), 22 (LNγ1), and 2E8 (LNγ1) were also included. (B) Arrows indicate bands of 230, 220, and 180 kDa, corresponding to LNβ1, LNγ1, and LNα4 chains, respectively. Under nonreducing conditions (C), most antibodies react with a band of nearly 630 kDa. (D) The ability of mAbs to (co)immunoprecipitate the LNα4 chain from platelet lysate is shown. LNα4 chain was visualized with mAb 6C3 as a major band of 180 kDa. In addition to 4 mAbs to LNα4 (3H2, 5D8, 6C3, and 9B2), mAbs DG10 (LNβ1) and LN-41 (LNγ1) were used for immunoprecipitation. OD indicates optical density.