Experiments were conducted to determine the principal mode of inheritance for antibody response to SRBC in selected populations of chickens and their crosses. Additive genetic variation was important in the inheritance of both primary and secondary responses to this antigen. Reciprocal differences and heterosis also influenced the secondary response. Kinetics of primary and secondary antibody responses were evaluated in pairs of lines divergently selected for high (HW) or low (LW) juvenile body weight and high (HA) or low (LA) response to SRBC antigen. Different groups of chickens were sampled on Days 3 to 7, 10, 14, 24, 26, 28, and 31 postprimary inoculation (PPI). Half of the chickens sampled after Day 14 received an additional injection of SRBC antigen. Plasma from each individual was examined for total, mercaptoethanol-resistant, and mercaptoethanol-sensitive titers. Antibody titers PPI to SRBC were consistently highest in Line HA and lowest in Line LA. Lines HW and LW reacted similarly to Line LA early in response, but showed higher levels later. In both primary and secondary responses, the weight lines peaked at similar levels. Thereafter, Line LW maintained a higher antibody titer level to SRBC antigen than Line HW.

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