Haplotype-specific differences in signaling by transfected class II molecules to a Ly-1+ B-cell clone.

CH12.LX B cells are responsive to antigen-dependent differentiative signals transmitted through their surface Ek molecules. Although CH12.LX cells express surface Ak molecules with normal protein sequence, the Ak molecules do not deliver differentiative signal to these B cells. To determine whether introduction of a new A molecule into CH12.LX cells would correct this deficiency, CH12.LX cells were transfected with the genes encoding new Aalpha and/or Abeta molecules. It was found that transfected cells responded to antigen-specific signals delivered via the Ealphak Ebetak, Aalphab Abetab, or Aalphak Abetab molecule. However, the B cells did not respond to signals generated by the molecule Aalpha kAbetak, Aalphab Abetak, Aalphak Abetad, or Aalpha kAbetau. Comparison of these sequences suggests that two Abeta residues, His-47 and Trp-197, are important to the transmission of differentiative signals to B cells.