CD68 antibody is a widely used tool in immunohistochemistry to identify cells of the monocyte-macrophage lineage. The CD68 protein, encoded by the *CD68* gene in humans, is a transmembrane glycoprotein predominantly localized in lysosomal compartments. It belongs to the lysosome-associated membrane protein (LAMP) family and is highly expressed in tissue-resident macrophages, histiocytes, and myeloid cells. Structurally, CD68 contains a conserved lysosomal targeting motif and scavenger receptor cysteine-rich (SRCR) domains, suggesting roles in phagocytosis, cell-cell interactions, and lysosomal trafficking.
CD68 antibodies (e.g., clones KP1. PG-M1) target specific epitopes on the protein, aiding in macrophage detection in paraffin-embedded or frozen tissues. Its expression is upregulated during monocyte-to-macrophage differentiation, making it valuable for studying inflammatory diseases, tumor-associated macrophages (TAMs), and atherosclerosis. However, CD68 is not entirely macrophage-specific; weak expression occurs in dendritic cells, fibroblasts, and some cancer cells.
While CD68 remains a gold-standard pan-macrophage marker, its utility in distinguishing macrophage subsets (e.g., M1/M2) is limited compared to newer markers like CD163 or CD206. Antibody performance may vary depending on fixation methods, necessitating validation for specific applications. Despite these limitations, CD68 remains indispensable in research and diagnostics for visualizing macrophage distribution and activation in pathological contexts.