Galectin-8 (Gal-8) is a mammalian lectin endowed with immunostimulatory ability. In the present work, we demonstrate that Gal-8-glycan interactions on the surface of antigen-presenting cells (APCs) promote antigen binding and internalization, independently from antigen nature. Both Gal-8 and antigen were together internalized and localized in early endosomes. Interestingly, antigen processing by APCs was also accelerated in the presence of Gal-8 as a separate mechanism, distinct from the increased antigen internalization. Moreover, APCs pulsed together with antigen and Gal-8 were able to activate cognate CD4⁺ T cells more efficiently than those pulsed with antigen alone. This enhanced antigen presentation was still evident in the absence of costimulatory signals and APCs-derived soluble mediators. Therefore, our results provide evidence for as yet unrecognized mechanism by which Gal-8 stimulates the elicitation of the immune response in a lectin-dependent manner, by inducing antigen uptake and processing upon lattice formation at APCs surface.

Galectin-8 (Gal-8) 是一种具有免疫刺激能力的哺乳动物凝集素。在目前的工作中，我们证明抗原呈递细胞（APC）表面的 Gal-8-聚糖相互作用促进抗原结合和内化，与抗原性质无关。Gal-8 和抗原一起内化并定位于早期内体中。有趣的是，APC 的抗原加工在 Gal-8 存在下也加速了，作为一种独立的机制，与增加的抗原内化不同。此外，与抗原和 Gal-8 一起脉冲的 APC 能够比单独用抗原脉冲的 APC 更有效地激活同源 CD4 ^{+ T 细胞。}在没有共刺激信号和 APC 衍生的可溶性介质的情况下，这种增强的抗原呈递仍然很明显。因此，我们的结果为尚未认识的机制提供了证据，通过该机制，Gal-8 通过诱导抗原摄取和 APC 表面晶格形成时的加工，以凝集素依赖性方式刺激免疫反应的引发。