Immunological characteristics of Hatano high-and low-avoidance rats

Hatano high- and low-avoidance (HAA and LAA) rats have been genetically selected on the basis of their two-way active avoidance behavior, and have been shown to differ in other behavioral and hormonal parameters. Since close interconnections among the nervous, endocrine and immune systems have been well documented, these two strains might possess differences in aspects of immunological action. In Experiment 1, plasma levels of IgG, IgM, complement 3 (C3), classical pathway hemolytic complement (CH50) and beta(2)-microglobulin were compared between males of the two strains at 5 and 24 weeks of age. Plasma levels of IgG and CH50 were lower in LAA than HAA rats at 5 weeks of age, whereas those differences disappeared at 24 weeks of age. There were no differences between the two strains in plasma levels of IgM, C3 and beta(2)-microglobulin. In Experiment 2, antibody production to sheep red blood cells (SRBC) and mitogen-induced lymphocyte proliferation were compared between 12-week-old males of the two strains. Antibody responses in the PFC assay, plasma anti-SRBC-IgM levels and spleen weights were higher in LAA than HAA rats. LPS-induced lymphocyte proliferation was greater in LAA than HAA rats. It was concluded that HAA rats show earlier development of immunological development, but that antibody production and mitotic response of B lymphocytes may be more pronounced in adult LAA than HAA rats. The strain differences observed in the immunological response may indicate the usefulness of using Hatano rats in studies of behavioral-immunological relationships.