Immune complexes in children with leukemia relationship to‐disease characteristics and to antibody response to mycobacterium bovis (BCG) in patients receiving BCG immunotherapy

The incidence and possible clinical relevance of immune complexes in sera from children with acute leukemias was investigated. Determinations were made in sera obtained at three‐month intervals from individual patients over a two‐year period. Two tests, the C1q binding and the polyethylene glycol precipitation assays, were employed. At time of diagnosis, immune complexes were found in sera from 6 of 41 patients (15%) with acute lymphoblastic leukemia (ALL). Three of 6 patients with T‐cell leukemia had immune complexes at diagnosis as compared to 3 of 35 with null‐cell leukemia. Only 1 of the 6 patients with T‐cell leukemia had a white blood cell count of less than 50,000/μl³. Of the patients followed for six months or more, 34% had immune complexes during therapy and the incidence of relapse was unrelated to the presence or absence of immune complexes. Fifty‐two percent of patients that remained in remission during the period of study and 5 of 8 patients that relapsed (63%) had immune complexes at one time or another suggesting that the presence of immune complexes by themselves did not portend either a favorable or an unfavorable prognosis. Sera taken at the time of diagnosis from children with acute non‐lymphoblastic leukemia (ANLL) had a higher incidence (36%) of immune complexes than similar sera from ALL patients (15%). Antibodies in sera from leukemia patients at diagnosis had a lower capacity to bind a BCG antigen than did sera from control subjects. Eleven of 17 patients that had BCG immunotherapy had a humoral antibody response to BCG. There was no relation between an antibody response to BCG and a favorable clinical response.