Dennis Justin Spencer *

Presented by Vincent A. Fischetti
B.S., Morehouse College
Determining the Phenotypic and Genotypic Response Exhibited by Streptococcus Pyogenes at the Human Palatine Tonsil

A child that gets a group A streptococcal infection that is adequately treated will not suffer any major consequences, however a pharyngitis (or strep throat) from the same organism could result in rheumatic fever and rheumatic heart disease. Although intensive research into the cause of rheumatic fever has gone on for decades, a clear picture as to the connection between the throat infection and heart damage is still unclear. One of the research tools used to examine the infection process of streptococci is a collection of human pharyngeal cells in culture, the only cell line available from the human oral cavity. These cultured cells have been used for decades to examine the attachment and invasion of streptococci and the genes responsible for this event. However, streptococci do not infect pharyngeal cells, they specifically target the tonsils causing tonsillitis.

When Dennis Spencer joined my lab he wanted to examine streptococcal interactions with tonsillar cells, to see if they differed from pharyngeal cells. He found that when he used human tonsillar tissues discarded from surgical procedures, the variability in his results were such that clear decisions could not be made. However, like much of science, a bit of luck came his way. In his reading, he discovered a paper in which a surgical group reporting on head and neck cancers identified two cancers in human tonsils. Dennis contacted the authors and received samples of these cells. He then began an extensive characterization and compared them to the pharyngeal cell line. What he discovered was that they were good representatives of tonsillar cells because they had not changed as a result of the cancer. More importantly, the streptococci were able to attach and invade these tonsillar cells 10 times better than the pharyngeal cells. Furthermore, when he examined the streptococcal genes that were turned on during this interaction, he found several candidates that had not been described before.

We believe that this tonsillar cell line will soon replace the pharyngeal cells in further studies of streptococcal infections, and in doing so may point the way to finally understanding the connection between the throat and the heart.

Of all the students and postdocs that I’ve had over the years, Dennis is by far the best dressed and loves to wear a bow tie on special occasions. On a more serious note, Dennis devotes a lot of his time mentoring students, not only in the lab but also on the national level with his eight-year affiliation with the Student National Medical Association.

Dennis is now very busy doing his clinical studies at Weill Cornell Medical College; in fact they gave him the day off today so he could graduate. I am happy to report that his experience in the lab has turned his attention to ear, nose and throat as his medical specialty.