Comparative Sequence Analysis of cDNA Clones Encoding I-A Molecules of the CH12 B Cell Lymphoma: Nucleotide Differences do not Account for their ‘Defective’ Function in B Cell Stimulation

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Abstract
The CH12 B cell lymphoma can be stimulated to secrete antibody by helper T cells that interact with I-EK but not I-AK molecules expressed on its membrane. Both molecules present antigen to the appropriate T cells. We have analyzed the mRNA by Northern blot analysis and obtained partial sequences of cDNA clones encoding Aα and Aβ of the I-A molecule to determine if deletions or mutations in the cytoplasmic or transmembrane domains account for the “defect” in triggering following interaction with I-A restricted helper T cells. The results provide no evidence for structural alterations in either Aα or Aβ which could account for these observations. The implications of these findings on the role of class II molecules in B cell activation is discussed.
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