Effect of diphtheria toxin on the viability of phagocytes and B-lymphocytes in animals sensitive and insensitive to it

It is well known, that mechanism of diphtheria toxin (DT) action triggers only if toxin penetrates into acid endosome after binding with specific receptor--heparin-binding epidermal grows factor like grows factor (HB-EGF) on the cell surface. We have suggested that DT is capable to penetrate either into B-lymphocytes, which have specific immunoglobulin receptors for DT or into phagocytes, which are able to phagocytosis of DT, because in both of these cases toxin get in endosome with conditions suitable for its activation. To check this hypothesis the comparative studies with insensitive to DT mice lacking specific receptor for DT, and with sensitive to DT guinea pigs were performed. Influence of DT on vitality of phagocytes and B-cells with different specificity from mice and guinea pigs was studied. B-cells were obtained from animals immunized by control antigen--ovalbumine and recombinant diphtheria toxoid--DT without N-terminal 28 aminoacid residues responsible for toxic effect. The results obtained have showed that DT can penetrate into phagocytes and B-cells specific to DT and kill these cells even if they lack classic receptor for DT. This fact evidences that DT is potentially able to inhibit self-directed antibody response and keep from participation of phagocytes in the protection of organism from infection.