Intralymphatic histiocytosis comprises M2 macrophages in superficial dermal lymphatics with or without smooth muscles

Intralymphatic histiocytosis represents a rare reactive disorder, which is characterized by the accumulation of macrophages within lymphatic vessels and observed predominantly in upper extremities. The infiltration and preferential M2 differentiation of macrophage are observed in chronic lymphedema, and lymphedema is considered a causative factor of intralymphatic histiocytosis. However, what causes accumulation of histiocytes in the lymphatic vessels remains unclear, and investigation regarding the characteristics of the macrophages has not been evaluated. We present a case of intralymphatic histiocytosis, in which immunohistochemical staining for both macrophages and lymphatic vessels was performed to evaluate the nature of macrophages within lymphatic vessels and to determine the causative factor. Aggregated macrophages were shown to be M2 macrophages positive for CD68, CD163 and CD206 but negative for inducible nitric oxide synthase. Thick lymphatic vessels positive for D2‐40 and α‐SMA in the superficial dermis were observed. We speculate that chronic lymphedema leads to hypertrophy of lymphatic vessels with smooth muscle in the superficial dermis, which may be a kind of malformation, and these lymphatic vessels produce some chemokines that induce intralymphatic aggregation of macrophages.     

Measurements of oxygen tension in tissues with a micro oxygen electrode

The electrode we have devised consists of a glass-insulated, recessed gold cathode with a tip of about 1 μm. The methods used in its construction, and that of a double-barrelled electrode, are described. To assess its validity for intracellular measurement of PO₂ we have used several tests, some of which are discussed in detail. The most unique consists of measuring the oxygen profile in freshly excised brain tissue or a yeast-agar mixture. A rearrangement of the classical diffusion equation to $\text{(P}{}_{\mathrm{<mtext>o</mtext>}}\text{? P)}\text{X}$ (P_o = PO₂ at surface; P = PO₂ at known depths from the surface; X = depth from surface) plotted against X should give a straight line down to very low values of PO₂. In vivo measurements made with this electrode indicate that cell PO₂ normally fluctuates with time, and the mean cell PO₂ is usually lower than the PO₂ in the venous outflow.