Are B lymphocytes involved in allograft/tumor rejection and GVH?

Several earlier observations by us and other investigators led us to propose a thesis that B lymphocytes, when activated by a virus, allo-antigen or bacterial protein would enter into effector arm of the immune response and cause allograft and tumor rejection or GVH-type of lesion in immunosuppressed animals. These effector cells may act directly in the process by contact with other cells or liberating cytokines. Such an hypothesis needs further support from experiments involving cancer and transplantation patients' B cells.