Human T-T cell bybridomas: development and applications

Human T-T cell hybrids are developed by fusing activated T lymphocytes exhibiting a desired immunologicalfunction or producing soluble factors with a human tumor T cell line with the objective to immortalize the T cell properties of interest. Mutagenized human tumor T cell lines, deficient for the enzyme hypoxanthine-guanine phosphoribosyl transferase have been usedfor the development of T-T cell hybrids. Unfused tumor cells are removed by using appropriate selection media. Certain of these media contain components (such as thymidine) that inhibit the growth of the hybrids. A different method involves the use of tumor T cell lines chemically treated, before the fusion, with irreversible biochemical inhibitors. This treatment eliminated any unfused cells of the T cell line. Recently, a method has been developed for the generation of human T-T cell hybrids without the use of mutagenized or chemically treated tumor T cell lines. Hybrids are selected on the basis of their ability toform colonies in soft agar, and their hybrid nature is confirmed by HLA typing andfunctional tests. The human lymphoblastoid cell lines used did not form colonies in agar. Hybrids developed by this method exhibit excellent growth characteristics and increased stability. A large number of human T-T cell hybrids producing growth, differentiation or immunoregulatory factors have been developed. Certain hybrids exhibiting immunological functions requiring direct cell-cell contact have been developed also. The advantages of using T-T cell hybrids over other methods for immortalizing T cell functions or lymphokine production are summarized. Also, the obstacles in developing T-T cell hybrids are discussed. The development of human T-T cell hybrids could befacilitatedfurther if a human tumor T cell line is identified with superior fusion efficiency.