Is Phaseolus vulgaris Leucoagglutinin (PHA-L) a Useful Marker for Labeling Neural Grafts?

The lectin Phaseolus vulgaris leucoagglutinin (PHA-L) has come into wide use as an anterograde neuroanatomical tracer. The ability of this lectin to fill entire neurons and remain in place over long periods suggested it might be an ideal marker for donor cells to be grafted into hosts for long survival periods. We have used the lectin PHA-L to mark fetal rat olfactory bulb (OB) cells prior to grafting into host rat OBs. Hosts were sacrificed at various times up to 9 weeks after grafting, and tissue was immunohistochemically processed for PHA reactivity. After 2 and 4 weeks survival, sparse patterns of labeled cells were observed within the host OBs. However, after 9 weeks survival, few if any labeled cells were visible within host tissue. We conclude that PHA-L may be a less than satisfactory marker for fetal rat cells (other than astrocytes) which are to be identified in host tissue after a period of several weeks.