Monoclonal antibodies demonstrate the organization of axons in the leech

Monoclonal antibodies have been generated that bind to subsets of neurons within the leech central nervous system (Zipser, B., and R. McKay (1981) Nature 289: 549-554). In this report we describe the binding patterns of monoclonal antibodies to subsets of axons in the leech using HRP-immunohistochemistry. Each antibody has a characteristic staining pattern in the connective, the large bundle of axons that runs the length of the nerve cord connecting each ganglion to its rostral and caudal neighbors. These staining patterns are consistent along the rostrocaudal axis of each animal, between animals of the same species, and, in many cases, between animals of different species. These results show that axonal position, like neuron cell body position, is a consistent feature of the organization of the leech central nervous system. Two antibodies bind to all of the axons in particular fascicles that are delimited by glial cell processes; another binds to single axons in fascicles that contain other, unstained axons. The grouping of antibody-identified axons into fascicles does not correlate in a simple way with the grouping of neuron cell bodies identified with the same antibody. The presence of one of these antigens on the surface of axons suggests a possible role in axon fasciculation. This report shows that molecular heterogeneity is a property of axons as well as of neuron cell bodies and demonstrates the organization of specific antibody-identified groups of axons within the connective.