Antibodies to Rat Macrophages

Introduction: In this short article we present the most important products for detection of rat macrophages in different tissues.

( For antibodies to human and mouse macrophages see FocusOn 10, 27 and 45 ).

The ED Clones

ED1 monoclonal antibody recognises a single chain glycoprotein of 110 kD that is expressed predominantly on the lysosomal membrane of myeloid cells. Weak cell surface expression also occurs. The antigen is expressed by the majority of tissue macrophages and weakly by peripheral blood granulocytes. Studies have shown that the antigen recognised by ED1 is the rat homologue of human CD68.

ED2 antibody reacts with a membrane antigen (175, 160 and 95 kDa) on resident rat macrophages. Monocytes, dendritic cells (spleen and lymph node), peritoneal granulocytes and other cell types are negative. ED2 discriminates between thymic cortical (positive for ED2) and medullary (negative for ED2) macrophages. It is useful to stain synovial lining cells and Kupffer cells in the liver. The antigen has recently been shown to be identical with CD163 (Polfliet, M.M.J. et al [2002].

ED3 recognises the rat CD169 cell surface antigen, a 185 kD molecule expressed by macrophages, predominately confined to lymphoid organs only. Monocytes and granulocytes are negative. No other cell types are positive. The most conspicious property of ED3 is it stains marginal zone macrophages and marginal metallophils in the spleen very strongly. Furthermore, macrophages in (auto-immune) diseased tissues express the ED3 antigen. In healthy tissue no expression occurs. CD169 is a receptor for glycoconjugates containing sialic acid. All ED clones can be used for histochemisty and flow cytomerty applications.

Clone RM1

RM-1 antibody recognizes a surface antigen of unknown function on monocytes, macrophages, interdigitating cells and their in vitro equivalents. The antigen is found on a subpopulation of most tissue fixed macrophages. It is quite predominant on red pulp macrophages and interdigitating cells in the outer periarteriolar lymphatic sheath of the spleen, the inner border of marginal sinus of lymph nodes, and alveolar macrophages. Langerhans cells of the skin and twisted spindle-shaped cells of the omentum are detected by the antibody. It is absent from sinusoidal endothelial cells and parenchymal cells.

Clone KiM2R

Ki-M2R is an antibody that recognizes typical tissue macrophages and specifically discriminates between monocytes (Ki-M2R-) and macrophages(Ki-M2R+). It stains all resident macrophages including those of bone marrow, lymphatic sinuses, lymphoid follicles, splenic red pulp, and Kupffer cells in the liver. Langerhans cells, interdigitating reticulum cells, and dendritic reticulum cells of lymphoid follicles are not stained. Ki-M2R is a reliable tool for indicating macrophage differentiation in vivo and in vitro.

Clone TRPM-3

TRPM-3 is a specific cell surface marker useful for the identification of tissue fixed rat macrophages and macrophage subpopulations. It is particularly suitable for phenotyping macrophages of lymphoid organs, where it reacts with marginal zone macrophages and with marginal metallophils. It is also an interesting marker for studying autoimmune diseased tissues. The antigen is comparable to the one recognized by clone ED3.

Table 1: Available antibody panel to Rat Macrophages

CD68 (Macrosialin, ED1) antibody, CD163 (ED2) antibody, CD169 (ED3) antibody; antibodies to Macrophages (pan, RM1 ) / Macrophages (pan tissue fixed, Ki-M2R) and Macrophages (marginal metallophils, TRPM-3)