Immune spørgsmål

Jeg har et spørgsmål ang. immunologi. håber nogen her kan svare på det.

Two dissimilar inbred strains of mice, A and B, are crossed to yield an F1 hybrid strain, AB. If adult AB spleen cells are injected into a newborn B mouse, the spleen cells will survive and induce tolerance of strain A grafts in the recipient.

Now, how does matured lymphocytes induce tolerance in a newborn, supposedly it is the work of Th cells? I know newborns lack IL2 receptors but a explanation for the mechanics of this kind of tolerance induction is appreciated.