Natural cytotoxicity toward K562 cells by macaque lymphocytes from infancy through puberty: effects of early social challenge.

The consequences of a single maternal separation experience followed by reunion at 6-7 months of age was studied in socially housed pigtail (Macaca nemestrina) and bonnet (Macaca radiata) macaques. At 15 months, these subjects were removed from their natal group and placed in same species social groups, consisting of other separated and matched control subjects. Some subjects were followed until they reached an average age of 4 years while remaining in this group. Blood samples were drawn to permit assessment of the ability of peripheral blood lymphocytes to lyse, in vitro, K562 cells. Maternal separation failed to affect lysis of K562 cells acutely, although lysis by matched control subjects appeared to be transiently reduced 2 h after removal of the adult female. A longer-term influence was noted such that lysis of targets in previously separated subjects was greater than that in matched controls. Lysis rose over time regardless of species or experimental condition. A striking internal consistency in the lysis was also noted. Lysis was highly intercorrelated (r's > .60, p < or = .005) within subjects across time during baseline, separation, and reunion phases of the acute social challenge. In addition, there was a tendency for this correlation to hold over the longitudinal phases. Lysis of K562 targets by macaque lymphocytes would appear to possess trait-like stability; however, the range of lysis may be modified by early experiences.