Clonal competition and obscuration. A My-bi (□) and a Ly-bi (●) HSC clone from young B6 donors were identified in primary hosts by their lineage contribution. BM cells (5 × 106) from the primary hosts were then injected into secondary hosts either alone (A,C) or as an equal mixture (B,D,E). Repopulation levels were measured at the indicated time points after transplantation into the secondary host. The HSC clones were originally obtained from a B6-GFP and a B6-CD45.1 donor, respectively, and the progenies of the clones were readily distinguishable. (A) Percentage donor-type cells in 2 mice each that received either the My-bi or the Ly-bi HSCs. (B) Percentage donor-type cells in 4 mice that received a 1:1 mixture of the My-bi and the Ly-bi HSCs. (C-E) The level of myeloid cells (■), B cells (□), and T cells (▩) in the donor-type cells at 7 months after transplantation except for mouse mix 8, where 5 months of data are presented. (C) Lineage contribution in mice that received either My-bi or Ly-bi HSCs. L1, L2, and M1 and M2 in panel C are the same mice shown in panel A. (D) Lineage contribution derived from the My-bi (M) and Ly-bi (L) HSCs in the mixed hosts. Each panel labeled host 5, 6, 7, and 8 corresponds to the mix 5, 6, 7, and 8, respectively, in panel B. Bars labeled L show the cells derived from the Ly-bi HSCs and bars labeled M show the cells derived from the My-bi HSCs in each host. (E) The percentage of myeloid and lymphoid cells derived from the 2 HSC clones shown in panel D was combined for each host.
