Interaction of cholera toxin B subunit with T and B lymphocytes.

We have preparedI-labeled cholera toxin B subunit (I-labeled CT-B, a specific activity of 98Ci/mmol) and found that its binding to T and B lymphocytes from the blood of healthy donors was high-affinity (K2.8 and 3.0nM, respectively). The binding of labeled protein was completely inhibited by unlabeled thymosin-α(TM-α), interferon-α(IFN-α), and the synthetic peptide LKEKK that corresponds to residues 16-20 in TM-αand 131-135 in IFN-α, but was not inhibited by the synthetic peptide KKEKL with inverted amino acid sequence (K>10μM). Thus, TM-α, IFN-α, and the peptide: LKEKK bind with high affinity and specificity to CT-B receptor on donor blood T and B lymphocytes. It was found that CT-B and the peptide: LKEKK at concentrations of 10-1000nM increased in a dose-dependent manner the soluble guanylate cyclase activity in T and B lymphocytes.