Expression of laminin polypeptides in the adult mouse bone marrow (a-f), and human bone marrow (g-j). Double immunofluorescence staining with an antiserum reacting with laminin 1, β1, and γ1 polypeptides (a) and with an endothelial cell marker MECA-32 (b) shows expression of either laminin 1, β1, or γ1 chains in the artery, sinusoidal subendothelial basement membranes, and in the intersinusoidal spaces. Immunostaining with MoAb 4G6 (d) shows expression of laminin 5 chain in the arteriolar walls and in the subendothelial basement membrane of the sinusoids (arrows). Immunostaining with antibody 200 specific for laminin 1 chain (e) is negative. Laminin 2 chain, identified with antibody 8G11-D10 (f) is present only in the arteriolar walls. Laminin 4, identified with a polyclonal antiserum against a synthetic peptide corresponding to laminin 4 chain, is localized in the intersinusoidal spaces (h,i), and in the walls of arteries (i). Double immunofluorescence staining with antibody 4C7 against human laminin 5 chain (g) and with the antiserum against synthetic peptide of laminin 4 chain (h) shows expression of 5 and 4 chains in the arteriolar walls (arrows), and 4 chain also in the intersinusoidal connective tissue. Control immunostainings with nonimmune rabbit serum (NRS) (c, j) are negative. Laminin polypeptide chains detected by each antiserum or antibody are indicated in the lower left corners of the figures.