Social media have become a crucial medium for the viral spread of fake news. However, past researches have primarily focused on the causal motivations behind the spread of fake news, neglecting how users, through self-cognitive processes, can counteract the dissemination of fake news and build their own immunity. Based on the cue consistency theory and cognitive response theory, this study investigates how the online opinion climate influences users' ability to build immunity against fake news. The study considers the mediating role of users' reflexive open-mindedness and the moderating effect of social bots' disclosure. Using a situational experimental approach, the results indicate that an inconsistent and abundant online opinion climate enhances users' ability to identify and immunize against fake news. Furthermore, implicit disclosures by social bots assist users in critically evaluating the authenticity of news. This study provides new insights for social media platforms and corporate decision-makers in addressing fake news.