OUTLINE: Stored human samples, specimens, and data collected from patients previously enrolled in a terminated National Cancer Institute-Institutional Review Board clinical trial are analyzed for research studies*. Antibodies are neutralized to allow for correlation of ELISA assays for immunogenicity with neutralization assays, which require cytotoxicity assays. In cytotoxicity assays, fresh malignant cells are isolated from blood, bone marrow, lymph nodes, or other tissues and incubated with recombinant immunotoxins to determine their sensitivity. Soluble CD25 assays are used to analyze known marker for B-cell malignancies, particularly those that are CD25-positive. Other candidate tumor markers include soluble IRTA2, soluble CD22, and soluble mesothelin. Skin biopsies retained by the Clinical Pathology Lab are used to study capillary leak syndrome. Other research studies include HLA typing to correlate immunological parameters with response and the PAX-gene tube to obtain RNA for quantitative PCR, evaluate monoclonal immunoglobulin expression, study minimal residual disease, and characterize immunoglobulin gene usage and somatic mutation. RNA microarrays are used to study resistance to immunotoxins. Samples of blood are used to study mechanisms of hemolytic uremic syndrome (HUS) from anti-CD22 immunotoxins. DNA samples are analyzed for complement and/or Factor H mutations that would make a patient more susceptible to HUS. Samples are also analyzed for levels of immunotoxin in blood, urine, and other tissues and for quantification of tumor markers on malignant cells using flow cytometry assays.