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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]

Mother-reared and nursery-reared rhesus monkeys were evaluated during the first month of life to assess the effects of early rearing on endocrine status in infancy. Plasma cortisol and growth hormone (GH) levels were measured in two conditions: (1) basal and (2) 30 min following removal from either the mother or the nursery. Nursery-reared infants had lower basal GH levels and higher cortisol levels than did mother-reared infants. Both GH and cortisol levels rose significantly following separation and reached similar levels in the mother-reared and nursery-reared infants. Mother-reared animals exhibited higher GH levels in response to a pharmacological GH-stimulation test. Thus nursery rearing of primate infants significantly affected the baseline secretion of two important endocrine systems, but did not appear to alter markedly the acute endocrine response to a psychological stressor., (Copyright © 1989 Wiley‐Liss, Inc., A Wiley Company.)