Simple Sea Sponge Helps Scientists Understand Tissue Rejection

The redbeard sponge (Microciona prolifera) has a cell-to-cell recognitionsystem that, on a basic level, is similar to that of humans but muchsimpler. It’s also a good organism for laboratory research, since itscells and cell adhesion molecules can be isolated with simple, fast,and non-disruptive methods and studied, and because its fingerlikestructures make grafting experiments relatively straightforward.

Inexperiments carried out on these sponges this summer, Dr.Fernàndez-Busquets and his colleagues are studying the cells andmolecules believed to be involved in the process of tissue rejection.By grafting together pieces of different individual sponges that willreject each other—a process that approximates what sometimes happens inhuman transplants—the scientists have observed that cells known as graycells migrate to and amass at the graft site, a clear suggestion thatthey are involved in non-self tissue recognition and rejection.Researchers believe that gray cells may be a primitive form of ourimmune system’s human killer cells.

Fernàndez-Busquets has alsobeen researching the role of the molecule called aggregation factorproteoglycan, which he has recently identified as another potentialplayer in sponge tissue rejection reactions, and which is very easy tostudy in sponges. The human version of this molecule, which isdifferent from the sponge version but similar in structure, is alsobelieved to have important functions in cell-to-cell interactions, butis hard to study.

The ultimate goal of this research is toprovide insights into the machinery behind human tissue rejection andimmune responses in hopes of someday being able to control theseprocesses and save lives.