Utilization of an immunostaining technique to demonstrate heterogeneity in the content of dihydrofolate reductase in peripheral blast cells from a patient with acute lymphocytic leukemia.

Cultured human KB cells which developed resistance to increasing concentrations of methotrexate showed increased levels of dihydrofolate reductase (DHFR) as demonstrated by an immunobridge staining technique. Peripheral blast cells from a leukemic patient were examined for DHFR content during several courses of methotrexate therapy. The number of cells which demonstrated high levels of DHFR increased at the end of treatment. The content in each individual cell was heterogeneous, based on varied intensity of staining in each cell. This immunostaining technique, which utilizes an antibody to DHFR, may have the potential to be a useful tool in the clinic for predicting a patient's possible response to methotrexate therapy.