Leukocyte responses in two breeds of layer chicken that differ in susceptibility to induced amyloid arthropathy

Amyloid arthropathy in chicken can be induced by intravenous inoculation of an arthropathic and amyloidogenic Enterococcus faecalis in susceptible bre eds. The commercial brown layer hybrids (BL) are more susceptible to the di sease compared to their white counterparts (WL). The precursor of amyloid-a protein, which is serum amyloid-A (SAA)., is identical in WL and BL. To in vestigate the factors involved in the breed-restricted susceptibility to am yloid arthropathy, we studied the type of leukocyte response and inflammato ry reactions in E. faecalis-induced disease. In the BL, a significant dose dependent peripheral leukocytosis mainly by heterophils, and plasma cell in filtration in arthritic joints was found. In contrast, secondary lymphoid n odular aggregates in the synovial membrane were prominent in the WL. The ag gregates consisted mainly of CD8(+) T cells. The high number of circulating leukocyte and prolific plasma cell responses in the BL predict extensive h umoral and acute phase reactions. This is in agreement with literature data on suppressed T-cell function in casein-induced amyloid-susceptible mice s trains. The difference in leukocyte response and type of inflammation betwe en WL and BL, when arthropathic and amyloidogenic bacteria induce infection , in conjunction with susceptibility to amyloid arthropathy, is discussed i n view of the murine T-helper responses. (C) 2000 Elsevier Science B.V. All rights reserved.