Production of functional human T-T hybridomas in selection medium lacking aminopterin and thymidine.

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Abstract
The production of hybridomas between immunologically activated T cells and malignant T-cell lines offers a potentially unlimited source of soluble T-cell-derived products. Human T-T hybrids were described; their use was hampered by slow growth and chromosomal instability due partially to the presence of thymidine in the traditional hypoxanthine/aminopterin/thymidine (HAT) selection medium. The development of a rapidly growing hypoxanthine phosphoribosyltransferase-deficient human T-cell line designated J3R7, the use of azaserine/hyoxanthine (AH) medium as an alternative selection medium to HAT medium, and the production of functional T-T hybrids by using the J3R7 line and the AH selection technique are described. Hybrids selected in AH medium were 4-fold greater in number and 3-fold faster in growth rate than hybrids grown in HAT medium. No stable clones were obtained from HAT cultures while AH-derived hybrids were readily cloned by the method of limiting dilution. Evidence for hybridization included the presence of approximately twice the number of chromosomes in hybrids than in J3R7 cells; the presence on hybrid cells of the Leu-3a surface antigen, present on normal helper T cells but not on J3R7 cells; the expression of HLA antigens of both the normal T-cell partner and the J3R7 line; and the constitutive secretion of interleukin 2 from multiple hybrid clones but not from the J3R7 cell line. These clones have maintained their rapid growth, chromosome number, surface phenotype and constitutive secretion of interleukin 2 for 4 mo.