Early social deprivation in nonhuman primates: long-term effects on survival and cell-mediated immunity.

ABSTRACT

BACKGROUND: Early differential social experience of non-human primates has resulted in long-term alterations in behavior and neurobiology. Although brief maternal separation has been associated with changes in immune status, the long-term effects on survival and immune function of prolonged early social deprivation are unknown. METHODS: Survival rates were examined in rhesus monkeys, half of which had been socially deprived during their first year of life. Repeated measures of immune status were tested in surviving monkeys (18-24 years old). Peripheral blood T, B, and natural killer lymphocytes, macrophages, and monocytes were measured by flow cytometry. Functional cellular immune activity measures included T-cell proliferative responses to mitogens (concanavalin and phytohemagglutinin), T-cell memory response to tetanus toxoid antigen, T-cell-dependent B-cell proliferative responses to mitogen (PWM) and natural killer cell cytotoxic activity. RESULTS: Despite identical environments following isolation, early social deprivation resulted in a significantly decreased survival rate, males being particularly vulnerable to early death. Early social deprivation was associated with a decrease in the ratio of helper to suppressor T cells, and a significant increase in natural killer cell number and in natural killer cell activity in the surviving monkeys. No differences in T- or B-lymphocyte proliferation following mitogen or tetanus toxoid antigen stimulation were observed. CONCLUSIONS: Prolonged early social deprivation of non-human primates profoundly affected mortality and resulted in lifelong effects on cell-mediated immune status.