The present study aimed to reduce the expression of interleukin-1 receptor-associated kinase 1 (IRAK-1) in dendritic cells (DCs) by RNA interference (RNAi). Subsequently, its effects on the expression of costimulatory surface molecules, the release of inflammatory cytokines, and the proliferation of T cells during the activation process of DCs, were determined. RNAi was used to silence IRAK‑1 gene expression in DCs, followed by lipopolysaccharide stimulation. Flow cytometry was then used to detect the expression levels of DC surface molecules, including cluster of differentiation (CD)86, major histocompatibility complex class II and CD40. Quantitative polymerase chain reaction was conducted to detect the mRNA expression levels of Toll‑like receptor 4, IRAK‑4, IRAK‑1 and nuclear factor‑κB (NF‑κB) in DCs. In addition, ELISA was used to detect the release of the following inflammatory cytokines: Interleukin (IL)‑10, IL‑12 and tumor necrosis factor-α (TNF-α). The MTS assay was used to determine the effects of IRAK‑1 RNAi on T‑cell proliferation. Knockdown of IRAK‑1 gene expression in DCs significantly reduced the expression levels of costimulatory surface molecules and intracellular NF‑κB, decreased release of the proinflammatory cytokines IL‑12 and TNF‑α, increased release of the anti-inflammatory cytokine IL‑10, and significantly reduced the proliferation of T cells. These results suggested that suppression of IRAK‑1 gene expression may inhibit the differentiation and maturation of DCs via the downregulation of DC surface molecules, inhibition of intracellular signal transduction pathways, regulation of inflammatory cytokine release, and by reducing its promoting effects on T-cell proliferation.