Persistent Impairment in Humoral Immunity and B-lymphocyte Count in Patients Over 12 Years Treated with BFM 90-Based Combination Chemotherapy for Acute Lymphoblastic Leukemia.

[UNLABELLED] Acute lymphoblastic leukemia (ALL) treatment profoundly impacts immune reconstitution, particularly affecting B cells, T cells, natural killer (NK) cells, and humoral immunity. This study evaluates dynamic changes in lymphocyte subsets and serum immunoglobulin levels throughout ALL treatment. We analyzed 34 patients aged > 12 years with ALL receiving a modified Berlin- Frankfurt-Münster (BFM) regimen. Peripheral blood lymphocyte subsets (CD19 + B cells, CD3 + T cells, and CD16 + /CD56 + NK cells) were measured at diagnosis, postinduction, post-consolidation, and at maintenance-initiation. Serum immunoglobulin (IgA, IgM, IgG) levels were also assessed using nephelometry. At diagnosis, 31.65% of lymphocytes were CD19 + B cells, which significantly declined to 0.53% by maintenance-initiation ( = 0.000). The absolute CD19 + B cell count dropped from 1.15 × 10⁹/L at diagnosis to undetectable levels in 35.3% of patients by maintenance-initiation. CD3 + T cells, initially 55.53% of lymphocytes, progressively increased to 87.6% by maintenance-initiation, NK cell levels dropped post-induction (0.14 × 10⁹/L,  = 0.000) but partially recovered post-consolidation (0.30 × 10⁹/L,  = 0.007). Immunoglobulin levels progressively declined, with IgG levels dropping from 12.19 to 6.04 g/L ( = 0.000), and 100% of patients having subnormal IgG at maintenance-initiation. ALL treatment leads to severe and sustained B cell depletion, a relative increase in T cells, and fluctuations in NK cell recovery. These findings highlight potential immune impairment in ALL patients aged > 12 years of age receiving pediatric inspired Chemotherapy warranting further investigation into long-term immune recover.

[SUPPLEMENTARY INFORMATION] The online version contains supplementary material available at 10.1007/s12288-025-02050-7.