UBC Theses and Dissertations
Purification, biochemical analysis and sequencing of a novel murine T suppressor factor Chan, Agnes How-Ching
The work reported in this thesis involved the purification, biochemical analysis and sequencing of a novel suppressor factor secreted by a T cell hybridoma, A10. The factor, A10F, isolated from spent medium of A10 cells, was found to consist of two forms with molecular weights at 140 - 160 and 80 kD as suggested by NH₂-terminal sequencing, Western blotting and tryptic peptide mapping experiments. Both forms of A10F were found to be capable of suppressing the in vitro generation of cytotoxic T lymphocyte (CTL) specific for P815 cells by syngeneic (DBA/2) splenocytes. In vitro ³⁵S methionine labeling experiments clearly demonstrated that the 80 kD protein was a secretory product of the A10 cells. The protein, which was specific to the monoclonal antibody (B16G), was absent in the control NS1 and BW5147 cells. Biochemical analysis indicated that the 80 kD molecule, was either a degradation product or a monomer of the 140 - 160 kD molecule. Further degradation products such as the 32 kD molecules were also found. This peptide, however, did not seem to cause substantial suppression in the in vitro CTL assay. When the 140 - 160, 80 and 32 kD proteins were sequenced at the NH₂ terminus, both 140 - 160 and 80 kD proteins were found to possess the same NH₂ terminus sequence. The 32 kD protein, on the other hand, was found to have an NH₂-terminus quite different from that of the 80 kD protein. These findings suggested that the 32 kD fragment was probably located at the distal end of the 140 - 160 kD molecule.
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