Prolonged neutropenia in a novel mouse granulocyte colony-stimulating factor neutralizing auto-immunoglobulin G mouse model

Objective Therapeutic use of recombinant human cytokines in humans can result in the generation of drug-specific antibodies. To predetermine the maximum potential effects of a granulocyte colony-stimulating factor (G-CSF) neutralizing auto-immunoglobulin G (auto-IgG) response during recombinant human G-CSF therapy, we developed a mouse model of mouse G-CSF (mG-CSF) neutralizing auto-IgG response. Materials and Methods Mice were immunized and boosted with mG-CSF chemically conjugated to either keyhole limpet hemocyanin or ovalbumin on an alternating schedule. Sera were analyzed for mG-CSF–specific titers and full blood counts were performed on a Technicon H-1E. On day 252, tissues were collected for histology. IgG was protein A affinity purified from pooled mG-CSF autoimmune sera. Results Mice immunized with mG-CSF conjugates produced mG-CSF–specific auto-IgG responses that lasted for the length of the study. Significant neutropenia (pmax < 0.004) was concurrent with the rise in mG-CSF–specific IgG titers. However, neutrophil counts remained at not, vert, similar20% of preimmunization levels through day 252. Endogenous mG-CSF neutralizing auto-IgG had no significant effect on hemoglobin, erythrocyte, lymphocyte, eosinophil, basophil, and platelet counts, and had minor, transient, or no effects on monocyte counts. Bone marrow colony assays from mG-CSF autoimmune mice demonstrated no significant effect of G-CSF neutralization on the numbers or proliferative capacity of preneutrophil lineage progenitors. Purified IgG from mG-CSF autoimmune mice neutralized mG-CSF in vitro. Conclusion High-titer G-CSF neutralizing auto-IgG in adult mice partially inhibited steady-state granulopoiesis and had little or no effect on steady-state levels of other hematopoietic cells.