Properdin Levels in Individuals with Chemotherapy-Induced Neutropenia

<span class="paragraphSection"><div class="boxTitle">Abstract</div><div class="boxTitle">Background.</div>Neutrophils produce and carry key components of the alternative pathway (AP) of complement, including properdin (P). The effect of chemotherapy-induced absolute neutropenia on circulating P levels and AP function has not been previously established.<div class="boxTitle">Methods.</div>We prospectively measured free P levels in serum from 27 individuals expected to develop neutropenia after administration of chemotherapy for hematological malignancies in preparation for hematopoietic stem cell transplantation and here describe the relationship between serum P levels and the neutrophil count over time.<div class="boxTitle">Results.</div>When the absolute neutrophil count (ANC) was >500 cells/mm³ pre-chemotherapy, P levels were significantly higher than P levels associated with an ANC ≤500 cells/mm³ (median values 8392 ng/mL and 6355 ng/mL, respectively; <span style="font-style:italic;">P</span> = .001). Pairwise comparison between pre-chemotherapy P levels and P levels at initial or last documented neutropenia before recovery showed a significant decline (<span style="font-style:italic;">P</span> < .0001). No correlation was observed between P levels during neutropenia and after recovery of neutropenia in 20 subjects for which postneutropenia samples were obtained. A small but significant (<span style="font-style:italic;">P</span> = .02) decrease in AP hemolytic activity was noted between baseline (preneutropenia) and samples obtained at the onset of neutropenia, but only with low (6.25%) and not higher (12.5 or 25%) serum concentrations.<div class="boxTitle">Conclusions.</div>A decline in P levels and AP activity could contribute to the increased risk of infection in neutropenic patients and warrants further study.</span>

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