N6 -methyladenosine (m6 A) RNA methylation is a reversible posttranscriptional 
modification in eukaryotes involving three types of functional proteins: 
"writers", "erasers", and "readers". m6 A regulates the metabolism of messenger 
RNAs and noncoding RNAs through RNA structure, splicing, stability, export, and 
translation, thereby participating in various physiological and pathological 
processes. Here, we summarize the current state of m6 A methylation researches, 
focusing on how these modifications modulate the fate decisions of innate and 
adaptive immune cells and regulate immune responses in immune-associated 
diseases, including viral infections and cancer. These studies showed that m6 A 
modifications and m6 A modifying proteins play a critical role in pathogen 
recognition, immune cell activation, immune cell fate decisions, and immune 
reactions. m6 A is a novel regulator of immune system homeostasis and 
activation.