Preferential Development of γ/δ- Bearing T Cells in Athymic Nude Bone Marrow

Abstract

Pluripotent stem cells present in bone marrow are capable of migrating to the thymus where they differentiate into progeny that populate the peripheral lymphoid tissues with T cells (Abramson et al., 1977; Keller et al, 1985; Dick et al., 1985). Whether and to what extent stem cells become committed to T cells outside the thymus remains controversial. The strongest evidence that this can occur is provided by the fact that functional T cells can develop (albeit very slowly) in the complete absence of a thymus in nude mice (Hünig and Bevan, 1980; Lake et al., 1980; Maleckar and Sherman, 1987). In vivo reconstitution experiments have shown that nude bone marrow contains pluripotent stem cells (Kindred, 1979). Peripheral lymphoid tissues of old nude mice (4 to 5 mo) have been reported to contain T cells by cell-surface phenotype (MacDonald et al., 1986), T cell receptor gene mRNA expression (Yoshikai et al., 1986; MacDonald et al., 1987), and functional criteria (Hünig and Bevan, 1980; Miller et al., 1983; Maleckar and Sherman, 1987). However, peripheral lymphoid tissues of young nude mice (< 11 wk) would appear deficient in T cells (MacDonald et al., 1981; Miller et al., 1983). Whether the environment of the athymic nude mouse is more efficient in allowing the development of α/β or γ/δ T cell receptor bearing cells is unknown although one study (Yoshikai et al., 1986) suggests the latter.