Identification of a 40-kDa human protein that cross-reacts with prokaryotic hsp60/chaperonins

Cross-reactivity between the immunodominant bacterial hsp60 proteins and heterologous human target proteins has led to numerous hypotheses on the role of hsp60 in the pathogenesis of autoimmune disease. In this work, we describe a novel 40-kDa human protein that cross-reacts with bacterial hsp60 proteins. CCP40 (chaperone cross-reacting protein, 40-kDa) was identified in extracts from HL-60 (human promyelocytic leukemia) cells on Western blots probed with A57-E4, a monoclonal antibody specifying a linear polypeptide epitope common among the bacterial hsp60 proteins (Yuan et. al. (1992) Inf. Immun. 60, 2288-2296). CCP40 was detected in other human hematopoietic cell lines, but could not be detected in mature peripheral blood leukocytes. CCP40 was also expressed in human CD34+ peripheral blood progenitor cells, disappearing with cytokine-induced cellular maturation.