Anna E. Lumelsky

The inducible costimulatory (ICOS) molecule is expressed by activated T cells and has homology to CD28 and CD152. ICOS binds B7h, a molecule expressed by APC with homology to CD80 and CD86. To investigate regulation of ICOS expression and its role in Th responses we developed anti-mouse ICOS mAbs and ICOS-Ig fusion protein. Little ICOS is expressed by freshly isolated mouse T cells, but ICOS is rapidly up-regulated on most CD4(+) and CD8(+) T cells following stimulation of the TCR. Strikingly, ICOS up-regulation is significantly reduced in the absence of CD80 and CD86 and can be restored by CD28 stimulation, suggesting that CD28-CD80/CD86 interactions may optimize ICOS expression. Interestingly, TCR-transgenic T cells differentiated into Th2 expressed significantly more ICOS than cells differentiated into Th1. We used two methods to investigate the role of ICOS in activation of CD4(+) T cells. First, CD4(+) cells were stimulated with beads coated with anti-CD3 and either B7h-Ig fusion protein or control Ig fusion protein. ICOS stimulation enhanced proliferation of CD4(+) cells and production of IFN-gamma, IL-4, and IL-10, but not IL-2. Second, TCR-transgenic CD4(+) T cells were stimulated with peptide and APC in the presence of ICOS-Ig or control Ig. When the ICOS:B7h interaction was blocked by ICOS-Ig, CD4(+) T cells produced more IFN-gamma and less IL-4 and IL-10 than CD4(+) cells differentiated with control Ig. These results demonstrate that ICOS stimulation is important in T cell activation and that ICOS may have a particularly important role in development of Th2 cells.

Genetic testing, currently a diagnostic tool used by only a small fraction of the population, promises to become a routine and critical part of medical care and drug prescription in the near future. This change will come chiefly through improvements in pharmacogenomics, the use of genetic testing to tailor medical care to an individual's unique genetic makeup. Current regulation of genetic testing is inadequate to meet the challenges of this new regime. Federal regulatory agencies, and in particular the FDA, are currently unprepared for the dramatic increase in scope and complexity of both the prescription drug market and the genetic testing market that is likely to result from the rise of pharmacogenomics. Although government advisory committees and legal scholars have long called for reform of genetic testing regulation, they have focused excessively on the moral dilemmas raised by predictive genetic testing at the expense of the increasingly significant area of pharmacogenomic research. This article provides a brief description of genetic testing, pharmacogenomics, and the current regulatory system, and highlights several areas where change is long overdue.