Transcriptional coactivator that specifically associates with either POU2F1/OCT1 or POU2F2/OCT2 (PubMed:7859290). It boosts the POU2F1/OCT1 mediated promoter activity and to a lesser extent, that of POU2F2/OCT2 (PubMed:7779176). It recognizes the POU domains of POU2F1/OCT1 and POU2F2/OCT2 (PubMed:7779176). It is essential for the response of B-cells to antigens and required for the formation of germinal centers (PubMed:7623806, PubMed:7859290). Regulates IL6 expression in B cells as POU2F2/OCT2 coactivator (By similarity). {ECO:0000250|UniProtKB:Q64693, ECO:0000269|PubMed:7623806, ECO:0000269|PubMed:7779176, ECO:0000269|PubMed:7859290}. This is the function of POU2AF1 (POU class 2 homeobox associating factor 1, Ensembl gene identifier ENSG00000110777).