Establishment and characterization of adenosine deaminase-deficient human T cell lines

We have established long term cell lines from a patient with adenosine deaminase (ADA)-deficient severe combined immunodeficiency by stimulation of blood and bone marrow cells with PHA and IL-2 followed by transformation of the activated cells with the human retrovirus HTLV-I. Despite the absence of detectable T cells in the patients blood, cell lines grew that carried the phenotype of mature activated T cells. TJF-2, the line established from blood, was characterized in detail. The concentration of ADA in TJF-2 cells was less than 1% of normal (3.2 U vs 413.0 U). Studies withpharmacologic inhibitors of ADA suggest that the residual adenosine deaminating activity of TJF-2 is from an enzyme distinct from true ADA, a nonspecific aminohydrolyase. Growth of TJF-2 cells was hypersensitive to inhibition by 2'-deoxyadenosine compared to normal T cells (ID₅₀, 55 μM vs > 1000 μM). Analysis of 2'-deoxyadenosine-challenged cells showed that TJF-2 cells accumulated significant levels of deoxyadenosine triphosphate, whereas normal T cells did not unless they were also incubated with the ADA inhibitor deoxycoformycin. Southern and Northern blot analysis of these cells revealed a grossly intact ADA gene that produced a normal size ADA mRNA. Yet, despite ADA deficiency, cells of the TJF-2 line were otherwise indistinguishable from HTLV-I-transformed T cells derived from normal donors with respect to dependence on exogenous IL-2 for growth, clonal rearrangement patterns of TCR β-chain genes, response to PHA, and rapid restoration of cellular volume after hypotonic challenge. The TJF-2 line thus represents a unique HTLV-I-transformed human T cell line exhibiting ADA deficiency and its expected metabolic consequences.