COMPARISON OF IMMUNE-RESPONSES IN INBRED LINES OF CHICKENS TO EIMERIA-MAXIMA AND EIMERIA-TENELLA

Immune responses of 4 inbred lines of chickens, that differ in resista nce to Eimeria maxima and E. tenella, were examined. Significant diffe rences were found in in vitro proliferation of peripheral blood lympho cytes to E. maxima sporozoite antigen, the more resistant lines C and 7(2) having higher responses than the more susceptible line 15I. These differences existed pre-infection and were enhanced following both pr imary and a second infection. The proportions of lymphocyte subsets in the peripheral blood following primary infection also differed betwee n lines, with significantly higher percentages of CD8+ and TCR1+ lymph ocytes circulating in the more resistant birds. In contrast, there wer e few differences between lines in either resistance or in in vitro pr oliferation of peripheral blood lymphocytes to E. tenella sporozoite a ntigen either pre-infection or following a primary infection. However, after a second infection when there were significant differences in r esistance between lines, as measured by oocyst excretion, there were a lso significant differences in lymphoproliferation with the more resis tant lines 15I and 6(2) having higher responses than the more suscepti ble line C. Thus for E, maxima there is a direct relationship between resistance to infection and lympho-proliferation in response to parasi te antigen. This implies that differences in cellular immunity may acc ount for differences in resistance between lines, and since these spec ific responses are enhanced by infection they may also reflect importa nt immune mechanisms. For the rather less immunogenic E. tenella, the correlation between resistance and lymphoproliferation is not so clear . However, where there were significant differences between lines, i.e . after a second infection, the direct relationship between resistance and lymphoproliferation was upheld.