Delayed wattle reaction as a measure of cell-mediated immunity in the chicken.

The cell-mediated immune (CMI) response to diphtheria toxoid (DT) was studied in commercial broiler breeder lines. The chickens were immunized with DT in complete Freund's adjuvant 21 days before CMI assay by delayed wattle reactivity (DWR) to DT. The DWR was shown to be a valid measure of CMI and to correlate with spleen cell migration inhibition and blastogenesis assays of CMI in vitro. In addition, each criterion of CMI was met, except for the passive transfer of DWR. These criteria were delayed timing, gross morphology, histopathology of DWR, and effect of antilymyphocytic sera on DWR. The duration of DWR over a 1-year period differed in the two lines of chickens tested. A significantly greater DWR was found in one line with all birds remaining reactive for CMI whereas in the other line 16% did not have CMI by the end of the year. The differences may reflect genetic variability within and between lines in expression of CMI.