Retention of cyclic AMP response to TSH in a cloned human thyrocyte/ T cell hybridoma (HY 2-15)

Our observation of a human T cell leukemia cell (Molt 4) demonstrating low affinity thyroid-stimulating hormone (TSH) responses, as evidenced by generation of cyclic AMP, led us to test Molt 4 cells as a suitable partner for immortalizing high affinity TSH receptors present on human thyroid cells. Therefore, we generated a hybridoma (HY 2-15) by a fusion between thyroid monolayer cells from a patient with Graves' disease, and a hypoxanthine-aminopterin-thymidine (HAT)-sensitive variant of this human T cell leukemia line, Molt 4-8 AG^R. The hybrid nature of HY 2-15 was confirmed by DNA histograms using propidium iodide and flow cytometry. Karyotyping showed the HY 2-15 cells to have five sets of chromosomes and human leukocyte antigen (HLA) class I determination revealed the presence of an additional HLA class I antigen (A2) not present on the Molt 4 partner cells. The established, cloned, hybridoma cells showed a > 30-fold increase in cyclic AMP release after stimulation with bovine TSH (bTSH, 1 mU/ml) with a minimum detectable stimulating dose of < 10 μU/ml bTSH. However, no other thyroid-specific functions could be detected. Furthermore, HY 2-15 cells failed to express HLA class II antigens either constitutively or in response to recombinant human gamma Interferon (IF) and a variety of other stimuli, data similar to the Molt 4 partner cells but in contrast to human thyroid cells which show high sensitivity to gamma IF. The preservation of highly sensitive TSH responsiveness in a proliferating cell offers a unique approach to the study of human TSH receptor function.