Failure to find alloimmune memory in the resorption phenomenon of Botryllus cytomictical chimera.

It has been previously shown that mixed-cell chimeras may be established between different colonies of the compound tunicate Botryllus schlosseri given that they share one allele in common on the fusibility locus. However, one of the partners in each chimera is often resorbed. Here we tested for the existence of a memory component to this response, as measured by the accelerated interval to resorption of a second set of semiallogeneic colonies. Eight genetically unrelated colonies gave rise to eighteen chimeras. After a complete resorption of the "inferior" partners in these chimeras, secondary and tertiary sets of chimeras were established with some of them by fusion of the "superior" with naive subclones of the "inferior" partners. It is shown here that (a) when multiple chimeras are prepared using the same pair of colonies, subclones of only one of the partners are resorbed; (b) high variation in the time for resorption is recorded when several chimeras are prepared from any specific pair of colonies, and (c) the time for resorption is not related to the number of vessels connecting between the partners in the chimera, nor to their relative body sizes. Allospecific memory is not documented here and reasons for its absence are discussed.