The function of IL27RA (interleukin 27 receptor subunit alpha, Ensembl gene identifier ENSG00000104998) is as follows. Signal-transducing subunit for an heterodimeric cytokine composed of IL27/p28 and a soluble receptor EBI3 (PubMed:14764690, PubMed:36930708). Heterodimerizes with IL6ST/GP130 to mediate signal transduction in response to the heterodimeric cytokine IL27/p28-EBI3. This signaling system acts through STAT3 and STAT1 (PubMed:14764690, PubMed:38509369). Also acts as a signaling receptor as part of the humanin receptor complex; binding of MT-RNR2/humanin (HN) activates the intracellular JAK-STAT3 signaling pathway leading to neuroprotection (PubMed:19386761). Involved in the regulation of Th1-type immune responses (By similarity). Also appears to be involved in innate defense mechanisms (PubMed:14764690). {ECO:0000250|UniProtKB:O70394, ECO:0000269|PubMed:14764690, ECO:0000269|PubMed:19386761, ECO:0000269|PubMed:36930708, ECO:0000269|PubMed:38509369}.