4. What selection criteria do you plan to enploy? What are the 
exclusion and Inclusion criteria for the study? 
Patients may need 3-12 months for genetically corrected T cell precursors 
to differentiate and repopulate the Immune system. Therefore, a patient's 
health status will need to be sufficiently good to permit survival during this 
Interval . 
Selection criteria: 
A) ADA-deficiency SCID 
ADA deficiency is defined as the absence or <10? normal ADA activity in 
both erythrocytes and lymphocytes. SCID Is defined by the usual criteria of 
lymphopenia, absent proliferative responses of peripheral blood mononuclear 
cells to mitogen and antigens, and low or absent antibody levels. In utero 
Investigation for possible ADA deficiency will most likely occur only when 
there has been a prior affected child In the family with the findings of SCID. 
B) Absence of HLA-matched donor 
C) Disease status: 
ADA-deficient SCID patients can be divided Into four classes by age at 
presentation: 
a) Newborn identified In utero 
b) Infant Identified after typical SCID presentation 
c) Older child with partial ADA activity and SCID 
Each of these has both positive and negatives attributes for potential 
gene therapy: 
a) Neonates could be treated prior to acquisition of multiple opportunistic 
Infections and thus may best survive any lag phase before genetically-corrected 
cells can differentiate into functionally protective T cells. There is 
evidence of progressive deterioration of the immune system in the first year of 
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