Purification of Immature CD4+CD8+ Thymocytes by Panning with Anti-CD8 Antibody

互联网2014-02-13

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Most T lymphocytes of the immune system differentiate within the thymus along the CD4/CD8 developmental pathway by a highly ordered process termed thymic selection ( 1 , 2 ). The maturation status of thymocytes is commonly assessed by their expression of the coreceptor proteins CD4 and CD8 and their surface density of aβ T cell receptors (αβ TCR), ( 1 ). Three major subpopulations of T cells exist within the thymus that exemplify the progression of thymocytes along the CD4/CD8 developmental pathway:

1.	CD4 ⁻ CD8 ⁻ (double-negative) thymocytes which express no αβ TCR;
2.	CD4 ⁺ CD8 ⁺ (double-positive) thymocytes, which express no/low αβ TCR; and
3.	CD4 ⁺ CD8 ⁻ and CD4 ⁻ CD8 ⁺ (single positive) thymocytes, both of which express high surface density of αβ TCR ( 1 – 4 ), (Fig. 1 ).

Fig. 1. Intrathymic development of thymocytes along the CD4/CD8 developmental pathway. Immature CD4 ⁻ CD8 ⁻ thymocytes develop into progeny CD4 ⁺ CD8 ⁺ thymocytes which maintain low expression of αβTCR. Immature CD4 ⁺ CD8 ⁺ thymocytes expressing αβTCR of appropriate specificities are selected for further differentiation into mature T cells that express either CD4 (CD4 ⁺ CD8 ⁻ ) or CD8 (CD4 ⁻ CD8 ⁺ ) coreceptor molecules, but not both. Mature CD4 ⁺ CD8 ⁻ and CD4 ⁻ CD8 ⁺ thymocytes emigrate from the thymus to the periphery where they may localize in lymphoid organs (for example, lymph node or spleen).