Monoclonal antibodies made to chick mesencephalic neural crest cells and to ciliary ganglion neurons identify a common antigen on the neurons and a neural crest subpopulation.

We previously reported the production of monoclonal antibodies (Mabs) that identified cell surface components of cultured chick and quail ciliary ganglion (CG) neurons and of a subpopulation of neural crest (NC) cells from 31-hr chick embryos (stage 9). Here we demonstrate that another Mab, CG-14, which was prepared to nitrocellulose-immobilized, lightly fixed (0.125% paraformaldehyde) mesencephalic NC cells from 31-hr (stage 9) chick embryos, labels the same antigen(s) recognized by CG-1 and CG-4 on both the CG neurons and the subpopulation of NC cells. All three Mabs label a polypeptide of 75 kD on Western blots of one-dimensional SDS-polyacrylamide gels. CG-14 blocked the binding of CG-1 and/or CG-4 to the 75 kD band on Western blots and blocked the binding of CG-1 and CG-4 to CG and NC cells. CG-1 and/or CG-4 antibodies, in turn, blocked the binding of CG-14 to Western blots, as well as NC and CG cells. We had previously shown that antibodies CG-1 and CG-4 were synergistically cytotoxic for the majority (95%) of cultured CG neurons in vitro in the presence of guinea pig complement. Here we show that the antibodies, which are both of the gamma 2a subclass, are also cytotoxic for the NC cells that they label in vitro. After the cells are ablated in culture, no other cells bearing the antigen(s) recognized by any of the three Mabs appear over a 2.5-week period. CG-14, however, is not cytotoxic for either the CG or NC cell populations alone or in combinations with CG-1 or CG-4. These results confirm our original observation that cultured CG neurons and NC cells share cell-surface antigen(s). The antigen recognized by all three Mabs appears to be the same whether the immunogen used to produce the antibodies was CG neurons or NC cells. This finding encourages us to continue tests of the hypothesis that the subpopulation of mesencephalic neural crest cells contributes to the formation of the ciliary ganglion in the embryo. Further characterization of the antigen appears in the accompanying paper.