Surface interferon-γ receptor-1 expression and STAT1 phosphorylation. (A) Down-regulation of surface expression of IFNγR1 on mononuclear cells from the patient 322 days after allogeneic stem cell transplantation (160 days after complete donor stem cell engraftment). (B) Down-regulation of STAT1 phosphorylation following stimulation with IFNγ of cells from patient at the same time as in panel A. (C) Normal IFNγR1 expression on donor mononuclear cells and (D) normal STAT1 phosphorylation following IFNγ stimulation of donor cells. (E) STAT1 phosphorylation in response to IFNγ stimulation in normal cells cultured in the absence of M avium and (F) in the presence of M avium.