BOB.1, also know as B-cell-specific coactivator OBF-1 or OCA-B, is a lymphoid-specific transcriptional coactivator that interacts with the transcription factors Oct-1 and Oct-2. BOB.1 has been shown to be critical for the development of a normal immune response, where it mediates octamer-dependent transcriptional activity in B lymphocytes. It is also critically involved in the formation of germinal centers in secondary lymphoid organs. BOB.1 levels have been observed to be massively upregulated in germinal center B cells, as compared with resting B cells. The BOB.1 antibody labels B lymphocytes and plasma cells. It is expressed in various B-cell derived lymphomas and Hodgkin's lymphomas (HL). The expression of BOB.1 is high in nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), but low in classic HL.