Reduced proliferation of old alloreactive effector/memory CD4⁺ T-cells.

<p>Old alloreactive effector/memory CD4⁺ T-cells proliferate less in response to antigen. Following adoptive transfer of young or old 2×10⁶ transgenic CD4⁺ ABM T-cells nude B6 mice were engrafted with two bm12 skin transplants. One week later spleen (<b>A</b>) and dLN (<b>B</b>) were retrieved, leukocytes were stained for CD4, Vα2 and Vβ8 expression and the expression of different cell surface markers (n = 4). Relative numbers of CD69⁺ and CD25⁺CD4⁺ T-cells were reduced in recipients spleens after transfer of old alloreactive T-cells indicating an impaired activation and proliferation. Similarly, alloreactive effector/memory CD4⁺ T-cells were significantly reduced 7 days after restimulation in vivo (<b>A</b>). In contrast, enhanced early activation (CD69⁺) of old tg CD4⁺T-cells in draining lymph nodes did not lead to a stronger expansion of effector/memory T-cells most likely due to an impaired IL-2 production (<b>B</b>).