Hapten-cell conjugates in DNCB contact sensitivity. In vitro stimulation with DNP-conjugates optimally inducing contact sensitivity in vivo.

Until now in vitro stimulation tests have failed to detect DNCB contact sensitivity in guinea-pigs sensitized epicutaneously without the use of adjuvants. In this study DNP-conjugates optimally inducing contact sensitivity in vivo were tested for their capacity to detect DNCB contact sensitivity in vitro in a lymphocyte transformation assay. In vivo contact sensitivity measurements in guinea-pigs which had been immunized with different hapten-cell conjugates, showed that (1) living cells should be used for conjugation with the allergen, (2) macrophages are optimal carriers and (3) syngeneity is not required. Therefore, DNFB-coated peritoneal macrophages (viable when conjugated) were used as an antigen for in vitro stimulation. Using this conjugate, a highly reproducible antigen-specific increase in DNA synthesis could be obtained in lymph node lymphocytes from guinea-pigs that had been sensitized to DNCB by epicutaneous application of the allergen without the use of adjuvants.