Notably, while administration of ablating substances, such as CLL and DT, is associated with systemic depletion of macrophages, loss of SIGN-R1–expressing cells in CD19 KO hosts is selective to the spleen, where MZ B cells reside, providing important support to the contribution of local SIGN-R1 MZ macrophages to the response. The gene discussed is CD19; the disease is B-cell chronic lymphocytic leukemia.