Effects of laminin monoclonal antibodies on the development of cultured rat embryos.

Whole rat embryos (9.5 days of gestation) were exposed to six different monoclonal antibodies to laminin during 48 hr of culture. Four (LAM I, LAM V, 5A2, 9D2) of the six were teratogenic or lethal and two (LAM II, 5D3) were not toxic at comparable levels. Teratogenicity and lethality were not related to antibody level, subclass or affinity for whole laminin. Indirect immunofluorescence studies using mouse embryo sections revealed that the toxic antibodies bound in a diffuse manner, while the nontoxic antibodies showed distinct labeling of tissues. These observations suggest that previous varied responses seen in cultured rat embryos exposed to laminin antibodies obtained from humans, monkeys, and rats were the result of differences in the epitope specificity of those antibodies.