The B cell compartment of two chicken lines divergently selected for antibody production: differences in structure and function.

In the present study differences in the B cell compartment of two chicken lines selected for either high (H) or low (L) antibody response to sheep red blood cells (SRBC) are investigated. In non-immunized chicks, flow cytometry revealed generally more circulating Ig+ leukocytes in the H line, while in the L line slightly more CD4+ and in week 5, more CD8+ cells were found. In the L line spleen more CD8+ were found and in the H line spleen more CD4+ cells. In week 6, half of the chicks were immunized. Both lines were similarly affected by immunization. Immunization reduced the percentages of the circulating T cell subpopulations, while Ig+ cells were enhanced, compared with non-immunized chicks. Histological determinations with specific mAbs on spleens of young, non-immunized chicks, showed large dense T cell areas in the L line, while in the H line more and larger germinal centres were found. In the H line, also, more B cells were found in the peri-ellipsoid lymphoid sheaths (PELS). No line differences in mononuclear phagocytes were found other than associated with line differences in numbers of PELS and germinal centres. After immunization with TNP-BSA, both higher numbers of TNP-specific antibody producing cells and higher levels of circulating antibody were found in the H line. Moreover, more TNP-specific plasma cells were found in non TNP-immunized H line chicks, than in the L line chicks. The H line had also higher ELISA-titers to KLH 5 days after immunization with KLH. Therefore it was concluded that selection for antibody response has affected the B cell compartment. The H line has relatively more B cells and the splenic structure of the H line differs from the L line, in the H line probably resulting in a more optimal organization for antibody response to T cell dependent antigens.