Table 1 Known functions of microglial proteins investigated

Ionized calcium-binding adaptor molecule (Iba)1

Cytoplasmic protein constitutively expressed by microglia, upregulated in inflammation. Iba1 is involved in cytoskeletal reorganization, membrane ruffling of the microglial processes and actin cross-linking needed for cell migration [23], thus reflecting microglial motility and migration properties.

CD68

CD68 labels lysosomal and endosomal transmembrane glycoprotein of microglia, indicating phagocytic activity [33].

Human leukocyte antigen (HLA)-DR

HLA-DR is a Major Histocompatibility Class (MHC) II cell surface receptor which presents antigens to cells of the immune system eliciting an immune response, involved in the non-self recognition and upregulated in inflammation [34].

Macrophage scavenger receptor (MSR)-A

MSR-A is a lipoprotein receptor involved in direct ligand recognition and scavenging activity. Its mouse homolog, scavenger receptor A (SR-A), is associated with plaques and release of reactive oxygen species and neurotoxic substances by microglia upon stimulation with fibrillar Aβ [35]. We previously showed a clustering pattern of MSR-A-positive microglia round plaques in Alzheimer's disease [16] suggesting expression of MSR-A may cause immobilization of the microglia when they encounter plaques [16, 26].

CD64 (Fcγ receptor I)

CD64 is a cell surface receptor with high affinity for the Fc portion of immunoglobulin (IgG), triggering a monocyte/macrophage response [30]. Expression of CD64 reflects the presence of immunoglobulins in the brain and thus the involvement of systemic immunity [36]. Overall FcγRs are important for antibody-dependent cytotoxicity, antigen presentation via MHC, clearance of antibodies and phagocytosis [37].