Hematological Responses Associated with Resistance to Rous Sarcomas in Four Strains of Chickens1

ABSTRACT Forty-nine cockerels from four distinct breeding groups, with respect to genetic resistance to Rous sarcomas, were utilized to study the leukocytic response to Rous sarcoma induction, development and regression. Breeding groups included the Arkansas Station Giant Jungle Fowl (JF), White Leghorns (W.L.), the F, crosses of J.F. males mated to W.L. females (F,), and a line selected solely for regression of Rous sarcomas (R x R). Hematological data were collected prior to RSV inoculation, and then once weekly for five weeks after challenge. Values for each of the sampling periods were compared with weekly tumor development. Tumor responses varied in accordance with the respective genetic resistance of each breed; J.F. and R x R birds gave resistant responses, WL gave mostly susceptible responses, while the F, were intermediate between the two parental strains. The total number of leukocytes, when averaged over all six sampling periods, was higher in treated birds than controls for all breeding groups. The greatest leukocyte response in the resistant J.F. and R x R occurred at week 3, which corresponded to the time of expected tumor emergence. This response was less dramatic in the treated F „ and completely lacking in the susceptible W.L. Differential leukocyte counts indicated that the week 3 response for J.F. was due to an increase in lymphocytes, while the responses for R x R and F, were due to increases in lymphocytes and heterophils. Although the functional significance of these cells in resistance to induction and regression of tumors remain to be determined, these results suggest that lymphocytes may have a primary role in resistance to tumors with heterophils acting in a secondary manner