Immunoblotting of laminin  polypeptides in the bone marrow stroma. Immunoblotting of protein extracts from an EHS tumor (EHS), adherent cells from mouse long-term bone marrow cultures (LTBMC), adult mouse bone marrow (BM), human long-term bone marrow cultures (HuLTBMC), and laminin-1 isolated from EHS tumor (EHS-laminin) was performed. Antibodies used were: (1β1γ1), a polyclonal antiserum against the three chains of laminin-1; 1, MoAb 200 against laminin 1 chain; 2, MoAb 8G11-D10 against laminin 2 chain; 4, two polyclonal antibodies against a fragment of human laminin 4 protein (left), or a synthetic peptide corresponding to human laminin 4 chain (right) as an immunogen. C, control immunoblotting in the absence of primary antibody. The positions of a 200 and 70 kD molecular mass markers run in parallel are shown to the left of each blot.