Failure of T and B cell cooperation during graft-versus-host disease.

Possible explanations for the immune deficiency usually associated with graft-versus-host disease include defective lymphocyte differentiation and active suppressor cell mechanisms. The present observations in a patient with chronic graft-versus-host disease delineate yet another possible mechanism: a failure of successful interaction between competent patient lymphocytes. Thus, helper and suppressor T cells as well as precursor B cells for the generation of specific in vitro plaque-forming cell (PFC) responses were present among patient lymphocytes and could interact normally with cells from four unrelated normal donors and produce PFC responses. In contrast, patient cells failed to interact successfully with each other and generate PFCs. This suggests a highly (self-) specific block in cell interaction that could explain the inability of the patient to mount a PFC response in vitro as well as a number of antibody responses in vivo during this phase of his disease.