Expression of surface antigens recognized by the monoclonal antibody lan 3-2 during embryonic development in the leech.

The monoclonal antibody lan 3-2 was used as a marker for the developmental expression of surface antigens which are specific for the two pairs of nociceptive neurons and a subset of axons in the adult CNS of the leech. In Haemopis embryos labeling of both nerve fibers and cell bodies with the antibody appears as expected for a metameric animal in a rostrocaudal temporal gradient from about day 5-6. Surprisingly, all central cell bodies are stained by the antibody in early development. However, later in embryogenesis around day 17 the staining intensity of most cells decreases except for the nociceptive cells, which remain antibody-positive, and the adult staining pattern gradually emerges. In addition to describing the central staining pattern, we show that specific peripheral neurons associated with the segmental sensilla also are antibody-positive during development. The distribution and developmental expression of the lan 3-2-positive antigens are compared between two phylogenetically different species of leeches and the diversity of the staining pattern of the monoclonal antibody is discussed.