Rabbit vascular endothelial adhesion molecules: ELAM-1 is most elevated in acute inflammation, whereas VCAM-1 and ICAM-1 predominate in chronic inflammation

Abstract

Activation of the microvasculature is a major component of the inflammatory response. During inflammation the vascular endothelium not only becomes more permeable to plasma proteins but also develops adhesion molecules that initiate the local immigration of leukocytes. We describe herein the in vivo changes in the three major vascular adhesion molecules during the development and healing of two types of rabbit dermal inflammatory lesions: (1) acute lesions produced in rabbits by the topical application of 1% sulfur mustard (SM, the military irritant/toxicant); and (2) chronic (immune-mediated) lesions produced in rabbits by intradermal injections of Mycobacterium bovis (BCG), the vaccine strain of tubercle bacillus. In each case, frozen tissue sections were made from lesions of various ages and stained immunohistochemically for von Willebrand (vW) factor to measure the total functional microvasculature. The sections were also stained immunohistochemically for the vascular endothelial adhesion molecules ICAM-1, ELAM-1 (E-selectin), and VCAM-1, and for the leukocyte ligands for ICAM-1: LFA-1 (CD11a/CD18) and Mac-1 (CD11b/CD18). Infiltrating monocytes and lymphocytes expressed the LFA-1 ligand and infiltrating PMN expressed the MAC-1 ligand. The area of stained microvasculature per square millimeter of tissue section was determined with the use of a computerized image analyzer. Edema and cell infiltration spread apart the microvessels, changing the number of microvessels per square millimeter of tissue section. Three methods of assessing such changes are presented. In SM lesions, endothelial ICAM levels were decreased from normal by about 50% at 1 and 2 days (when the lesions reached their peak size) and returned to normal at 3 and 6 days (during the healing process). ELAM rose in peak SM lesions and remained high during healing. VCAM levels, however, were only elevated in the 6-day (almost healed) lesions. In BCG lesions the levels of endothelial ICAM and VCAM (and to a lesser extent ELAM) were increased at 9 days and remained so as the size of the lesions peaked at 23 days. During the healing phase at 37 days, the elevated ICAM and VCAM levels decreased but the slightly increased ELAM levels persisted. These findings indicate that ELAM plays a major role in acute inflammation and that VCAM and ICAM play major roles in chronic inflammation. VCAM is known to be monocyte and lymphocyte selective.

Nonspecific and immune-specific up-regulation of cytokines in rabbit dermal tuberculous (BCG) lesions

“…Vaccination of rabbits with BCG and removal of the resulting lesions New Zealand White rabbits (2.3-3.0 kg) were injected intradermally in multiple sites; each site received about 5 ϫ 10 6 Tice BCG [4]. The resulting lesions were measured with calipers, as described previously [34].…”

“…For the immunohistochemical procedures [4], the tissue specimens were not fixed in parformaldehyde, but were immediately frozen in O.C.T. embedding compound and stored as described above.…”

“…These procedures have been previously described in detail [4]. Briefly, they employed a primary antibody, a biotinylated secondary antibody to the IgG1 fraction of the primary antibody, and a diaminobenzidine-peroxidase color reaction produced with the ABC kit, i.e., the avidin-biotin-peroxidase complex (Vector Laboratories, Inc., Burlingame, CA).…”

“…For quantitation, the total microvasculature in representative areas was stained with a monoclonal antibody to Von Willebrand factor [4]. Then, with the probe of an image analyzer, the stained areas were outlined (not including the vessel lumens).…”

“…IL-1␤ and TNF-␣ are primary cytokines that up-regulate the production of other cytokines [1][2][3]. These primary cytokines also up-regulate adhesion molecules in the microvasculature that enable the diapedesis of mononuclear cells (MN) and polymorphonuclear neutrophils (PMN) into inflammatory sites [4][5][6]. MCP-1 is a C-C chemokine that attracts and activates MN, i.e., macrophages and lymphocytes [7][8][9].…”