Human alloreactive cytotoxic T-lymphocytes(HCTL)were maintained in a long-term culture, retaining function and specificity. By repeated addition of T cell growth factor(TCGF, Interleukin 2)obtained from supernatants of PHA stimulated peripheral blood lymphocytes, HCTLs grew continuously in vitro with a doubling time of 20 to 40 hours. During a 10 month culture period, these HCTLs have been cytotoxic but changed their specificity gradually, probably due to loss of some clones. Cloning of these HCTLs was successfully achieved by limiting dilution method. Primary clones were classified into several groups as follows; 1) Cytotoxic clones directed against classical HLA antigens. These are subdivided according to each HLA antigen involved. 2) Cytotoxic clones with unknown specificities. 3) Cytotoxic clones, mixture of 1) and 2). 4) Non-cytotoxic clones. Recloning of a primary clones(group 3)was done and revealed that this clone was not monoclonal, but a mixture of two cytotoxic clones. Although most of primary clones proved to be monoclonal, we found that the cloning procedure should be performed at least twice in order to obtain genuiness monoclonal T cell clones.
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