Antigen-induced T cell-replacing factor (TRF). III. Establishment of T cell hybrid clone continuously producing TRF and functional analysis of released TRF.

With the fusion of the AKR-derived T lymphoma cell line BW 5147 and Mycobacterium tuberculosis-primed and boosted BALB/c T cells, a T cell hybrid clone (B151K12) with the ability to continuously produce T cell-replacing factor (TRF) was established. Analysis of cell surface markers on the B151K12 hybrid cells revealed expression of both H-2D and H-2K region products as well as Thy-1 antigens derived from both parental cells. The mean number of chromosomes of the hybrid was 58, which was less than the sum of that of the 2 parental cells. The culture supernatant from the B151K12 clone induced an anti-DNP IgG-PFC response in T cell-depleted DNP-primed B cells. The T cell-replacing character of the supernatant was substantiated by its ability to induce anti-DNP IgG-PFC responses in DNP-primed B cells using hapten coupled to heterologous carrier, i.e., T cell-independent antigen (DNP-dextran) and a nonimmunogenic synthetic copolymer (DNP-D-GL). Anti-SRBC IgM-PFC responses in nu/nu spleen cells were also enhanced by the presence of the B151K12 culture supernatant. Both the secondary anti-BPO and anti-SRBC IgG-PFC responses in B cells primed with the respective antigens were strikingly enhanced by the addition of the B151K12 culture supernatant, indicating that the TRF from the monoclonal B151K12 hybrid could stimulate B cell responses in a totally antigen nonspecific manner. The supernatant from the B151K12 culture did not trigger anti-DNP IgG-PFC responses in DNP-primed B cells from DBA/2Ha and (DBA/2Ha × BALB/c)F1 male mice, which were defective in the acceptor site(s) for Tbc-TRF. This indicates that the TRF from the B151K12 clone acts on TRF-acceptor site(s) on B cells according to the same mechanism as seen with PPD-stimulated Tbc-primed T cells. This fact was further substantiated by means of experiments that blocked the activity on B cells of TRF from the B151K12 clone utilizing (DBA/2Ha × BALB/c)F1 male anti-BALB/c alloantiserum containing anti-TRF-acceptor site antibody.