Molecular characterization of the V regions of four IgE antibodies specific for trichosanthin.

We report here the cDNA cloning and variable region nucleic acid sequences of the heavy and the light chains of four monoclonal IgE and one monoclonal IgG1 antibodies against trichosanthin (TCS), all of which recognized a similar or related antigenic determinant. Sequence analysis revealed that the VH regions of the four IgE antibodies use different V gene segments from the 7183, 36-60 and J558 families. The DH genes varied extensively in nucleotide sequence and length, with D segments DSP2, DFL16 and DQ52 being used with equal frequency. All JH gene segments except JH1 were present in the epsilon transcripts. In contrast, there appeared to be restricted L-chain utilization. All four L-chain V genes cloned belonged to the V kappa 21 family and a bias in the use of J kappa 1 gene was also observed. The VL sequences of the anti-TCS monoclonal antibodies showed much less diversity than the VH sequences. We propose that the L-chain rather than H-chain may play a more significant role in specific binding with allergenic determinant on TCS.