Delayed hypersensitivity to hapten-protein conjugates. II. Anti-hapten specificity and the heterogeneity of the delayed response.

The cross-reactions of conjugates carrying structurally related haptens have been studied in guinea pigs with delayed sensitivity to hapten-protein conjugates. The specificity of the delayed reaction has been found to be a function both of the nature and of the position of the substituent on the benzene ring; the cross-reactions shown in the delayed system, however, have been found to be appreciably more extensive than those reported for rabbit antibody systems employing identical haptens. This finding supports the earlier suggestion that the determinant in the delayed system is functionally larger than that required for reaction of antigen with conventional antibody. Desensitization studies with cross-reacting antigens have indicated that the delayed hypersensitivity response is characterized by the production of a heterogeneous population of cells, all more or less closely adapted to the structure of the homologous hapten conjugate.