Diagnosis of haematological disease using anti-i. I. Disorders with lymphocytosis.

Using cytotoxicity and antibody-binding tests, the i antigen was measured on the blood lymphocytes of normal subjects and of patients in whom a diagnosis of chronic lymphocytic leukemia (CLL) was considered because of a slight lymphocytosis in the blood and bone marrow. Among 25 patients, 15 had a normal amount of i antigen; in 10 there was a marked reduction in i antigen, such as is found in typical CLL. Similar studies were done on lymphocytes from 15 patients with clinical and morphological findings usually associated with lymphosarcoma cell leukemia (LSL). Nine had a normal amount of i antigen; in six there was a marked reduction of i antigen, suggesting a diagnosis of CLL. A study of the subsequent clinical course and final diagnosis in these patients suggests that the reduction in lymphocyte i antigen characteristic of typical CLL occurs in patients with early CLL who have only slight lymphocytosis, but not in patients with slight lymphocytosis from other causes. Similarly, a reduction in lymphocyte i antigen is found in patients with morphologically atypical CLL but not in patients with LSL.