Expression of T cell activation antigen CD134 (OX40) has no predictive value for the occurrence or response to therapy of acute graft-versus-host disease in partial T cell-depleted bone marrow transplantation

CD134 (OX40) is a member of the tumor necrosis factor family which is expre ssed by activated T lymphocytes, CD134 expression on T cells was monitored during the first 35 days post-transplant in 14 patients, receiving either a n HLA-identical sibling bone marrow transplant (BMT), a matched unrelated t ransplant (MUD-BMT) or an autologous peripheral blood progenitor cell trans plant (PBPCT). The sibling and unrelated grafts were partially depleted of T cells, CD134 expression on CD4(+) T cells peaked between 7 and 14 days af ter BMT, with a mean peak value of 45 % of CD4(+) cells (range 26-70 %) ove r all three patient groups, The observed pattern of CD4(+)CD134(+) expressi on, an increase during the first 2 weeks post-BMT followed by a gradual dec line towards values of 15-40%, was similar in all groups, No difference in the kinetics of CD134 expression by CD4(+) T cells was observed between the patients that did or did not develop graft-versus-host disease (GVHD), nor did the clinical effect of any treatment given for GVHD correlate with alt erations in CD134 expression by CD4(+) T cells, Absolute CD4(+),CD134(+) T cell numbers showed a more rapid increment after autologous PBPCT than afte r sibling or MUD transplants, We conclude that expression of CD134(+) by CD 4(+) T lymphocytes cannot serve as a surrogate marker for allo-reactivity, CD134(+) expression may reflect lymphocyte regeneration, rather than allore activity.