Vibrio cholerae hemolysin is apoptogenic to peritoneal B-1a cells but its oligomer shepherd the cells for IgA response.

Vibrio cholerae hemolysin (HlyA) can exist as a monomer with hemolytic activity and an oligomer that agglutinates erythrocytes. Biochemical differences accompanying the change in state of aggregation led us to weigh possible differences between the two forms from mucosal immunoregulation perspective. HlyA oligomer-treated murine B-1a cells up-regulated TLR2 and involved the signaling molecules MyD88, TRAF6 and NF-kappaB. The cells subsequently expressed IgM and IgA. HlyA monomer treatment although resulted in TLR2 up-regulation, could not induce these effects. Apoptosis was detected in majority of the monomer-treated cells that involved caspase-9 and caspase-3. This study shows for the first time that two forms of the same protein could drive the host immune cell to two different outcomes, one of death and the other towards activation.