Human Gene Therapy Subcommittee - 7/30/90 
4. Figure 2 was clarified. It is now clear that the 
proliferative responses of the peripheral blood T 
lymphocytes of the patients make it likely that this is 
a polyclonal response and that the patient's peripheral 
blood cells are capable of responding to antigens. 
5. The issue of the diagnostic bands and staining was made 
clearer. However the question remains as to whether 
the insertion of the ADA gene is not a prerequisite for 
the antigen-specific immune function because the 
peripheral blood T cells in this patient are capable of 
antigen-specific function in terms of blastogenesis and 
can cooperate with B cells to make specific antibody 
before the gene is inserted. It appears that the 
insertion of the gene permits the cells to survive in 
vivo in the mouse and shows that this result is like 
the NIH investigators' data indicating that ADA- 
containing T cells survive longer in culture than T 
cell lines that do not contain the vector. 
Dr. Parkman said his interpretation of the data was that the 
insertion of the human ADA gene into ADA-deficient T cells 
permits the T cells to survive longer in vivo than mock-infected 
cells. The investigators' hypothesis is that insertion of this 
gene into the peripheral T cells of patients who have a lesser 
degree of immune function would allow the prolonged survival of 
the cells, some of which would be antigen-specific and therefore 
would have a damming effect, or recruitment effect, on antigen- 
specific T cells. Further, the main point of the data is that 
the insertion gene has nothing to do with antigen-specific immune 
function, but rather has primarily to do with persistence of 
these cells in vivo in this model system. 
Dr. Mulligan asked if there was a need to culture these cells 
quickly and whether the assay system was functional. Dr. 
Bordignon said that if the cells are cultured for a long time 
they do not engraft. He noted this result may have to do with 
down-regulation of cell surface molecules and their ability to 
pass the peritoneal barrier in mice and may not be relevant to 
human engraftment. He said it had not been studied thoroughly 
because it was set aside when it was found that it did not work. 
Dr. Mulligan questioned whether the persistence was due to in 
vitro cultivation of the cells or whether the persistence was 
merely due to gene transfer. He said he thought the actual 
virus-producing cells have an effect on infection but do not 
necessarily have an effect on bone marrow. Dr. Bordignon agreed 
with Dr. Mulligan and said his data suggested this was the case. 
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Recombinant DNA Research, Volume 14 
