Types And Distribution Of Leukocytes

The most striking differences in cell type and distribution were observed with mast cells and macrophages (see Figure 9.3). In both gaiter and thigh biopsies, mast cell numbers were two to four times greater than control in Class 4 and 5 patients around arterioles and PCVs (p < 0.05). Class 6 patients demonstrated no difference in mast cell number compared to controls. Mast cell numbers around capillaries did not differ across groups in either gaiter or thigh biopsies. Macrophages demonstrated increased numbers in Class 5 and 6 patients around arterioles and PCVs, respectively (p < 0.05). Differences in macrophage numbers around capillaries were observed primarily in Class 4 patients in both gaiter and thigh biopsies. Surprisingly, lymphocytes, plasma cells, and neutrophils were not present in the immediate perivascular space. Fibroblasts were the most common cells observed in both gaiter and thigh biopsies. It was speculated that mast cells and macrophages may function to regulate tissue remodeling resulting in dermal fibrosis.40 The mast cell enzyme chymase is a potent activator of matrix metal-

FIGURE 9.3 Electron micrograph (Mag 4300x) of mast cells (MC), macrophages (MP) and fibroblast (F) surrounding a central capillary from dermal biopsy of a patient with CEAP class 4 chronic venous insufficiency.

Pericapillary Cuff

FIGURE 9.3 Electron micrograph (Mag 4300x) of mast cells (MC), macrophages (MP) and fibroblast (F) surrounding a central capillary from dermal biopsy of a patient with CEAP class 4 chronic venous insufficiency.

loproteinase-1 and -3 (collagenase and stromelysin).47-49 In an in vitro model using the human mast cell line HMC-1, these cells were reported to spontaneously adhere to fibro-nectin, laminin, and collagen types I and III, all components of the perivascular cuff (see later).49 Chymase also causes release of latent TGF-pi secreted by activated endothelial cells, fibroblasts, and platelets from extracellular matrices.50 Release and activation of TGF-pi initiate a cascade of events in which macrophages and fibroblasts are recruited to wound healing sites and stimulated to produce fibroblast mitogens and connective tissue proteins, respectively.51 Mast cell degranulation leading to TGF-pi activation and macrophage recruitment may explain why decreased mast cell and increased macrophage numbers were observed in Class 6 patients. Macrophage migration, as evidenced by the frequent appearance of cytoplasmic tails in perivascular macrophages, further substantiates the concept of inflammatory cytokine recruitment (see Figure 9.4).

0 0

Post a comment