| Abstract: | Lymphocyte function was evaluated in 26 untreated children with acute lymphoblastic leukemia (ALL) and 5 patients with acute myelogenous leukemia (AML) by stimulation with phytohemagglutinin (PHA) in dose- and time-response studies. The response to PHA correlated positively with the percentage of lymphocytes (r = + 0.786) and negatively with the percentage of lymphoblasts (r = ? 0.728). Sixteen patients with a WBC < 20,000/cu mm (51 ± 5% lymphocytes, 28 ± 7% lymphoblasts, and 39 ± 20% T cells) responded normally (81,156 ± 8,229 cpm) on the fourth or fifth day of culture. Ten patients with a WBC > 20,000/cu mm (10 ± 3% lymphocytes, 88 ± 4% lymphoblasts and 18 ± 28% T cells) had a significantly lower response to PHA on these days (13,609 ± 5,568 cpm). Six of the ten high-WBC patients had a delayed peak response on the sixth or seventh day of culture. This abnormal response to PHA is similar to that which has been described in patients with chronic lymphatic leukemia and is at least partially due to the dilution of a normal lymphocyte population by the proliferation of a population of non-PHA-responsive lymphoblasts. The remaining four high-WBC patients had flat PHA dose- and time-response curves and a poorer clinical course. Two of them had T-cell leukemia. The absence of response to PHA in these children may characterize a group of patients with acute lymphoblastic leukemia who are immunodeficient at the time of diagnosis and may reflect the presence of a unique population of lymphoblasts with suppressor activity. |
