Detection of macrophage migration inhibitory factor by monoclonal antibody in Sézary syndrome.

We have reported previously on the generation of a monoclonal antibody against human macrophage migration inhibitory factor (MIF), which is a mediator of cellular immunity. Macrophage migration inhibitory factor activity in the migration assay was closely correlated with antibody reactivity. Using this antibody called 1C5/B, we are now able to study the expression of MIF in situ. Here, we report on the detection of MIF in blood lymphocytes and skin of a patient with a leukemic cutaneous T-cell lymphoma with the characteristics of Sézary syndrome. Ninety percent of the patient's Ficoll Hypaque-isolated peripheral white blood cells were of the helper phenotype. By conventional immunoperoxidase method, 94% reacted strongly positive with the antibody 1C5/B. In contrast, using the immunofluorescence method only 25% reacted positive. This indicates that the majority of the tumor cells did not express the molecule on their membrane but only in the cytoplasma. No other marker, such as interleukin 2 receptor, HLA-DR antigen, or interferon-gamma could be related to the expression of MIF. Also the cellular infiltrate in the skin was composed mainly of T helper cells and reacted positive with 1C5/B. As less than 3% of normal blood lymphocytes reacted with 1C5/B we suggest that the conversion to positivity may be a characteristic feature of the leukemic T-cell phenotype in Sézary syndrome.