Gene therapy has been thought of as the ultimate form of treatment for
inherited diseases. The concept of correcting the fundamental genetic
errors leading to human diseases is certainly more appealing than att
empts to treat the infectious, metabolic, and other undesirable conseq
uences of defective gene function. In the last decade, gene therapy ha
s moved from that speculation to early clinical applications with clin
ical gene transfer protocols applied to a variety of disorders includi
ng inherited genetic defects, malignancies, and infectious diseases. I
nborn errors of immunity have played a key role in the development of
these early gene therapy strategies and have paved the way to a broade
r application of this novel branch of medicine. In this article, we su
mmarize the molecular aspects of clinical gene transfer and review rec
ent results and future prospects of gene therapy applications for immu
nodeficiency diseases.