CD64: The potential therapeutic target of the myeloid cells

• Gene Information: FCGR1A (encoding CD64) is a protein-coding gene located on chromosome 1q21.2. It synthesizes the high-affinity Fc-gamma receptor Ia (FcγRIA), a transmembrane glycoprotein belonging to the immunoglobulin receptor superfamily.
• Protein Expression: CD64 is predominantly expressed on cells of the myeloid lineage. Under steady-state conditions, CD64 is readily detectable on circulating monocytes, macrophages, and dendritic cells. During infection or inflammation, CD64 can be markedly induced on neutrophils and other myeloid populations in response to cytokine-mediated signals.
• Signaling Pathway: CD64 transduces signals by binding the Fc domain of monomeric IgG and associating with an ITAM-bearing Fc receptor gamma chain (FcRγ) to trigger downstream Syk kinase cascades.
• Therapeutic Inhibition: By targeting CD64, the high-affinity monomeric IgG receptor, therapies either block immune complex engagement to dampen autoimmune inflammation or deliver cytotoxic payloads to selectively eliminate CD64⁺ malignant and immunosuppressive cells.

CD64

• The full length mouse Fcgr1 gene that includes the promoter, 5’UTR, signal peptide, extracellular domain, transmembrane domain, cytoplasmic domain and 3’UT Rare replaced by human FCGR1 counterparts in B hCD64 mice plus.

Mouse and human CD64 expression analysis in blood. Blood were collected from wild-type C57BL/6JNifdc mice (female, 6-week-old, n = 3) and homozygous B-hCD64 mice plus (female, 6-week-old, n = 3). CD64 expression on myeloid cells was analyzed by flow cytometry using anti-mouse CD64 antibody (Biolegend, 139309) and anti-human CD64 antibody (Biolegend,  305008). 

Mouse and human CD64 expression analysis in spleen. Splenocytes were collected from wild-type C57BL/6JNifdc mice (female, 6-week-old, n = 3) and homozygous B-hCD64 mice plus (female, 6-week-old, n = 3). CD64 expression on myeloid cells was analyzed by flow cytometry using anti-mouse CD64 antibody (Biolegend, 139309) and anti-human CD64 antibody (Biolegend, 305008). 

Mouse and human CD64 expression analysis in bone marrow. Bone marrow were collected from wild-type C57BL/6JNifdc mice (female, 6-week-old, n = 3) and homozygous B-hCD64 mice plus (female, 6-week-old, n = 3). CD64 expression on myeloid cells was analyzed by flow cytometry using anti-mouse CD64 antibody (Biolegend, 139309) and anti-human CD64 antibody (Biolegend, 305008). 

Mouse and human CD64 expression analysis in peritoneal lavage. Peritoneal lavage were collected from wild-type C57BL/6JNifdc mice (female, 6-week-old, n = 3) and homozygous B-hCD64 mice plus (female, 6-week-old, n = 3). CD64 expression on myeloid cells was analyzed by flow cytometry using anti-mouse CD64 antibody (Biolegend, 139309) and anti-human CD64 antibody (Biolegend, 305008). 

Mouse and human CD64 expression analysis in blood, spleen, bone marrow, peritoneal lavage. Splenocytes, peripheral blood, bone marrow and peritoneal lavage were isolated from female C57BL/6JNifdc and B-hCD64 mice plus (female, 6-week-old, n = 3). CD64 expression was analyzed by flow cytometry using anti-mouse CD64 antibody (Biolegend, 139309) and anti-human CD64 antibody (Biolegend, 305008).

√: Expression of CD64 protein can be detected; ×: Expression of CD64 protein can not be detected; ND: Not detectable.

1. Karel F. A. Van Damme et al. Cross species cellular mapping and humanization of Fcγ receptors to advance antibody modeling. Science immunology. 2026

SPM:small peritoneal macrophages
LPM: large peritoneal macrophages

Analysis of leukocyte subpopulations by flow cytometry in immune organs and blood. Splenocytes, peripheral blood, and lymph nodes were isolated from female C57BL/6JNifdc mice and B-hCD64 mice plus (female, 6-week-old, n=3). Single live cells were gated on the CD45⁺ population and analyzed by flow cytometry as indicated. Values are expressed as mean ± SEM.

Analysis of T-cell subpopulations by flow cytometry in immune organs and blood. Splenocytes, peripheral blood, and lymph nodes were isolated from female C57BL/6JNifdc mice and B-hCD64 mice plus (female, 6-week-old, n=3). Single live cells were gated on the CD3⁺ T-cell population and analyzed by flow cytometry as indicated. Values are expressed as mean ± SEM.