601 IMMUNE STATUS OF CHILDREN WITH ACUTE LYMPHOBLASTIC LEUKEMIA (ALL) IN PROLONGED REMISSION (CR)

Abstract

With the marked improvement in survival in childhood ALL, it is increasingly important to correlate immune status with longterm disease control. 24 ALL patients, 7 in CR for 5-12 yrs. and off therapy for a x of 3.5 yrs., and 17 in CR on therapy for a x of 2.8 yrs. (.3-5 yrs.) were studied.

The mean % of sheep RBC rosettes (T-cell) on therapy (53%) and off therapy (50%) was similar to controls (60%). Complement receptor lymphocytes (B-cell) averaged 25.6 and 15.6% in patients off and on therapy, respectively, a significant difference (p< .05), but still WNL. Mouse RBC receptors, detecting a B-cell subgroup, were deficient in 93% of patients on and 40% of patients off therapy (p<.01). Stimulation by T (PHA, CON-A) and B (Saureus) cell mitogens was comparable (all p>.05) in the 3 groups of children after 3 or 6 days of culture. In 2 patients who relapsed, a marked reduction in all mitogen stimulation was noted at a time when there was no clinical evidence of relapse. None of the patients had cells reactive with either the antisera detecting la like or leukemia associated antigens (LAA), including the 2 in the pre-relapse state.

We conclude that these patients in prolonged CR have normal T-cell % and function. Maintenance therapy, however, does reduce a B-cell marker while mitogen response remains intact. Preliminary data suggest that mitogen response may be more sensitive than the reappearance of LAA in detecting impending relapse.

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