Furthermore, the protective effect of CD8<sup>+</sup> T cells was significantly enhanced in patients with severe immune disorder (interaction <i>P</i> = 0.034).<h4>Conclusion</h4>This integrated clinical-immune signature underscores the pivotal, threshold-dependent role of endometrial CD8<sup>+</sup> T cells and the cumulative burden of previous failures in RIF. Here, CD8A is linked to immune system disorder.