Immunosuppressive factor(s) specific for L-glutamic acid50-L-tyosine50. IV. In vitro activity and immunochemical properties.

The responsiveness of BALB/c spleen cells to the terpolymer L-glutamic acid60-L-alanine30-L-tyrosine10 (GAT), the copolymer of L-glutamic acid50-L-tyrosine50 (GT) and the corresponding complexes with methylated bovine serum albumin (MBSA) has been studied in vitro in a modified Mishell-Dutton culture system. Cultures of BALB/c spleen cells respond to GAT, GAT-MBSA and GT-MBSA over a wide dose range. Contrary to in vivo findings BALB/c spleen cell cultures respond to GT in vitro although in a much narrower dose range. Lymphoid extracts from GT-primed BALB/c or B10.BR mice (GT-TSF) specifically suppress the GT-MBSA response in vitro. This culture system has allowed us to further investigate immunochemical properties of both BALB/c and B10.BR GT-TSF-GT-TSF from both strains display affinity for GT-Sepharose and bear determinants encoded by the I region of the H-2 complex. Moreover, we demonstrate that the suppressive activity from B10.BR mice is a molecule or a molecular complex which displays affinity for GT and bears determinants of the I-J subregion of the H-2k haplotype.