Hanspeter Rolli

Potency of hexavalent and decavalent anaphylactogens: affinity enhancement by epitope clusters.

Two deca-L-lysine conjugates, one carrying ten, the other carrying six D-benzylpenicilloyl haptenic groups as epitope models, were used as elicitors of passive cutaneous anaphylaxis in guinea pigs. It was found that equal haptenic doses yielded virtually indistinguishable responses, i.e., the potencies were close to 10:6. Interpretation of these data appears possible by using established immunochemical concepts of preequilibria and equilibria in free solution as starting point. The discussion is simplified due to the fact that the two conjugates being decavalent and hexavalent, respectively, in free solution, are both hexavalent on cell membranes. It was found that the clusters of haptenic groups displayed by the conjugates enhance the affinity for antibody binding and that the haptenic densities are directly related to potencies. Epitope clusters of enhanced affinity interacting with cell-bound antibody may be significant and useful in a number of ways.

Anaphylactic properties of monohaptenic dinitrophenylated tripalmitoyl-S-glycerylcysteinyl lipopeptides

Tripalmitoyl-S-glycerylcysteinyl lipopeptides are B-cell and macrophage activating and may be used as low molecular weight immunogens of considerable potency and even as vaccines when conjugated with suitable epitopic structures. Selected lipopeptides carrying single Dnp haptens were found to evoke mild passive cutaneous anaphylaxis in guinea pigs sensitized against Dnp. The reactions were observed after intravenous injection whereas intradermally applied antigen was negative. The anaphylactogenicity seems unrelated to micelle or aggregate formation of the insoluble peptides which require lecithin additions as well as sonication to become solubilized. The dinitrophenylated lipopeptide tripalmitoyl-S-glyceryl-cysteinyl-seryl-lysine produced toxic reactions which were not observed with the lipopeptide devoid of Dnp. Dinitrophenylated tripalmitoyl-S-glycerylcysteiny-1,6-diaminohexane and tripalmitoyl-S-glyceryl-cysteinyl-lysine did not show these toxic reactions.

On the immunochemical specificity of pyrazolinone and pyrazolidinedione reactions

Haptenic groups based on the 1-phenyl-2,3-dimethyl-3-pyrazolin-5-one and 1,2-diphenyl-pyrazolidine-3,5-dione structures conjugated to human serum albumin gave antibody responses in rabbits which were compared with those raised against the same haptens conjugated via spacer bridges to the protein carrier. The spacing up to 12.4 A had no marked influence on the antibody specificity evaluated by haptenic inhibition of ELISA. The specificities are more pronounced than those found with e.g. anti-penicilloyl antibodies which seems in line with clinical experience involving e.g. phenylbutazone, sulfinpyrazone, propyphenazone and metamizole. It is argued that such strict specificities may lead to false negative tests in diagnostic procedures in vitro as well as in skin testing.