The present invention provides a method of providing an individual with a
biological factor or intermediate thereof which comprises introducing
into the individual Sertoli cells genetically altered to produce the
biological factor or intermediate thereof. The genetically altered
Sertoli cells are administered in an amount effective to produce the
desired effect. Aside from producing the biological factor or
intermediate thereof, the engineered Sertoli cells also create an
immunologically privileged site. Vectors comprising a promoter which
functions in Sertoli cells operably linked to coding sequence for a
desired biological factor are also provided as are Sertoli cells
comprising such vectors. A pharmaceutical composition comprising Sertoli
cells genetically altered to produce a biological factor is also
provided.