Serum concentrations of
CD8 antigen were measured at diagnosis with an
enzyme-linked immunoassay in children with
acute lymphoblastic leukemia (n = 344) or
non-Hodgkin's lymphoma (n = 65). All patients had detectable levels of the serum
antigen, which in its soluble nonreduced form appeared to be a 52-Kd homodimer as compared with the 66-Kd surface membrane component on most thymocytes and on a subset of functionally distinct T cells (suppressor/cytotoxic). Increased serum levels of CD8 in
leukemia patients were significantly related to recognized high-risk prognostic features: high leukocyte count, large liver and spleen size, high serum lactic
dehydrogenase level, T-cell immunophenotype, presence of a mediastinal mass, pseudodiploid karyotype,
DNA index less than 1.16, and
chromosomal translocation. Children with serum CD8 levels greater than or equal to 450 U/mL were more likely to fail treatment than were those with lower levels (P = .002), even in the group with non-
T-cell leukemia (P = .003). In a multivariate analysis, serum
CD8 antigen contributed independent prognostic information beyond that conveyed by age, leukocyte count, and race (P = .02). High serum
CD8 antigen levels also correlated with advanced stages of disease in children with
non-Hodgkin's lymphoma or
B-cell leukemia. Children with higher serum
CD8 antigen levels (greater than or equal to 700 U/mL) had a poorer treatment outcome (P = .003), even after results were adjusted for disease stage and serum lactic
dehydrogenase level (P = .05). Measurement of serum levels of
CD8 antigen not only has important prognostic value in childhood lymphoid
malignancies but also could be useful in assessing the immunoregulatory role of T cells in patients with
cancer.