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Individual variation in serotonergic function is associated with reactivity, risk for affective disorders, as well as an altered response to disease. Our study used a nonhuman primate model to further investigate whether a functional polymorphism in the promoter region for the serotonin transporter gene helps to explain differences in proinflammatory responses. Homology between the human and rhesus monkey polymorphisms provided the opportunity to determine how this genetic variation influences the relationship between a psychosocial stressor and immune responsiveness. Leukocyte numbers in blood and interleukin-6 (IL-6) responses are sensitive to stressful challenges and are indicative of immune status. The neutrophil-to-lymphocyte ratio and cellular IL-6 responses to in vitro lipopolysaccharide stimulation were assessed in 27 juvenile male rhesus monkeys while housed in stable social groups ( NLL = 16, NS = 11) and also in 18 animals after relocation to novel housing ( NLL = 13, NS = 5). Short allele monkeys had significantly higher neutrophil-to-lymphocyte ratios than homozygous Long allele carriers at baseline [ t(25) = 2.18, P = 0.02], indicative of an aroused state even in the absence of disturbance. In addition, following the housing manipulation, IL-6 responses were more inhibited in short allele carriers ( F1,16 = 8.59, P = 0.01). The findings confirm that the serotonin transporter gene-linked polymorphism is a distinctive marker of reactivity and inflammatory bias, perhaps in a more consistent manner in monkeys than found in many human studies. [ABSTRACT FROM AUTHOR]

Fourteen female monkeys (Macaca mulatta) received a trivalent influenza vaccine and antibody response was determined by a change in plasma antibody content (ELISA) before and after vaccine. Lymphocyte cultures were also established from these monkeys and the level of antibody response did not correlate with mitogen-induced lymphocyte blastogenesis or natural killer cell function. In vitro anti-influenza antibody synthesis, however, was found to correlate well with the in vitro response. That is, monkeys who were non-responders, as determined by lack of change in plasma antibody content, were also non-responders in vitro. Accordingly. we believe that vaccine response is not necessarily a measure of immune competence but its measurement may, none the less, have clinical utility. The excellent correlation of in vivo and in vitro response provides predictive value for the in vitro test. Furthermore, because the correlation is good, the in vitro test may be useful as a tool in immunopharmacology and toxicology. [ABSTRACT FROM AUTHOR]