The small blood vessels in areas of lymphocytic infiltration around malignant neoplasms

High endothelial venules (HEVs) in immunity, inflammation and cancer

High endothelial venules (HEVs) are specialized blood vessels mediating lymphocyte trafficking to lymph nodes (LNs) and other secondary lymphoid organs. By supporting high levels of lymphocyte extravasation from the blood, HEVs play an essential role in lymphocyte recirculation and immune surveillance for foreign invaders (bacterial and viral infections) and alterations in the body’s own cells (neoantigens in cancer). The HEV network expands during inflammation in immune-stimulated LNs and is profoundly remodeled in metastatic and tumor-draining LNs. HEV-like blood vessels expressing high levels of the HEV-specific sulfated MECA-79 antigens are induced in non-lymphoid tissues at sites of chronic inflammation in many human inflammatory and allergic diseases, including rheumatoid arthritis, Crohn’s disease, allergic rhinitis and asthma. Such vessels are believed to contribute to the amplification and maintenance of chronic inflammation. MECA-79⁺ tumor-associated HEVs (TA-HEVs) are frequently found in human tumors in CD3⁺ T cell-rich areas or CD20⁺ B-cell rich tertiary lymphoid structures (TLSs). TA-HEVs have been proposed to play important roles in lymphocyte entry into tumors, a process essential for successful antitumor immunity and lymphocyte-mediated cancer immunotherapy with immune checkpoint inhibitors, vaccines or adoptive T cell therapy. In this review, we highlight the phenotype and function of HEVs in homeostatic, inflamed and tumor-draining lymph nodes, and those of HEV-like blood vessels in chronic inflammatory diseases. Furthermore, we discuss the role and regulation of TA-HEVs in human cancer and mouse tumor models.

Morphological change in tumor endothelial cells induced by natural-type human tumor necrosis factor

The effects of natural-type human tumor necrosis factor (nh-TNF) on tumor endothelial cells of experimental brain tumors were investigated electron microscopically. Tumor vessels with hypertrophic endothelial cells were observed 12 and 24 hr after an intralesional administration of 5,000 U of nh-TNF. Increased biosynthetic organelles such as the Golgi complex and rough endoplasmic reticulum were evident in the plump cytoplasms. These endothelial cells resembled those in high endothelial venules (HEV) functionally characterized by the high permeability of leukocytes. In addition, close interactions between these endothelial cells and leukocytes were observed. Our findings indicated that nh-TNF could promote the morphological change in tumor endothelial cells into HEV-like cells.

Expression of adhesion molecules in the host response to colon carcinoma

Expression of the adhesion molecules LFA-1, ICAM-1, and VCAM-1 was studied in five resected colon carcinomas, one villous adenoma, and normal colon mucosa to determine whether expression of these markers is increased in response to tumor. Frozen tissue samples were stained by a labeled avidin-biotin technique using primary antibodies to LFA-1 (CD11a), CD2, CD4, CD8, CD20, CD68, HLA-DR, ICAM-1 (CD54), and VCAM-1. For each marker, the number of positive mononuclear cells was graded semiquantitatively, and stromal and endothelial cells were scored as either positive or negative. Overall grade of inflammation was increased in tumor compared with normal mucosa in five cases. Cells positive for LFA-1, CD2, CD4, CD8, and CD20 were increased in the tumors in the same cases. ICAM-1 was expressed in vessels, inflammatory cells, and stromal cells in normal mucosa. It was markedly increased in tumor stroma in all six cases. VCAM-1 was negative in normal mucosa, and focally expressed in tumor vessels and stroma. We conclude that increased expression of adhesion molecules occurs around colon neoplasms, particularly in stromal cells, and may be a mechanism for the recruitment of activated leukocytes as part of the inflammatory response to colon carcinomas.

Microvascular expression of MALA-2 correlates with in vivo lymphocyte trafficking and is preferentially enhanced in tumors by tumor necrosis factor-alpha and interleukin-1 alpha

The role of endothelial cell adhesion molecule expression in the immune response to tumors is unknown. We have investigated the expression of murine lymphocyte activation antigen (MALA-2), the murine equivalent of intercellular adhesion molecule-1 (ICAM-1), in blood vessels of normal murine tissues and in melanoma tumors and evaluated the relationship between MALA-2 expression and lymphocyte trafficking in vivo. C3H/HeN mice were injected both i.p. and s.c. with a clone of K-1735 syngeneic melanoma cells. Day 11 tumor-bearing mice were killed and vascular expression of MALA-2 was quantified using immunohistochemistry. MALA-2 expression was high in lung, liver and spleen and low in lymph node, small bowel, muscle and tumor. Systemic administration of either recombinant tumor necrosis factor alpha (rTNF alpha) or recombinant interleukin-1 alpha (rIL-1 alpha) over 2 days prior to organ harvest resulted in an increase in the number of tumor vessels expressing MALA-2, with no change in MALA-2 expression in other tissues. In vivo lymphocyte trafficking was evaluated using cultured, activated splenocytes radiolabeled with 111In. 111In-labeled splenocyte distribution correlated closely with MALA-2 expression, with high localization to spleen, liver and lung and poor localization to lymph node, small bowel, muscle and tumor. Systemic administration of rTNF alpha, but not rIL-1 alpha, resulted in a significant increase in 111In-labeled splenocyte distribution to tumor, but neither rTNF alpha nor IL-1 alpha altered 111In-labeled splenocyte distribution to normal organs. Our data demonstrate the in vivo pattern of vascular MALA-2 expression in normal murine tissues and tumors and suggest that the expression of MALA-2 can be preferentially enhanced in tumors by systemic administration of cytokines. Lymphocyte distribution in vivo correlates closely with the pattern of MALA-2 expression, and these data support the conclusion that MALA-2 plays an important role in the regulation of lymphocyte trafficking.

Interactions between interleukin-2-activated lymphocytes and vascular endothelium: binding to and migration across specialized and non-specialized endothelia

A prerequisite for the successful immunotherapy of solid tumours with interleukin-2 (IL-2)-activated lymphocytes is their ability to home to the tumour tissue. Lymphocyte homing is a complex process which is known to involve at least two independently regulated events: adhesion to the luminal surface of vascular endothelium and the subsequent transendothelial migration of lymphocytes. In this study we have used an in vitro model of lymphocyte homing which employs specialized high endothelium to ask whether IL-2-activated lymphocytes are able to migrate across vascular endothelium in order to leave the blood vessel. Both the adhesion of IL-2-activated cells and their migration across monolayers of cultured high endothelial cells (HEC) were increased in comparison with non-activated lymphocytes. The adhesion of IL-2-activated lymphocytes was mediated by lymphocyte function-associated antigen-1 (LFA-1) and a very late activation antigen-4 (VLA-4)-related pathway. LFA-1-dependent adhesion was mediated by ligands on HEC other than the intercellular adhesion molecule-1 (ICAM-1) and the VLA-4-related pathway was mediated by ligands other than the CS1 domain of fibronectin. HEC-adherent lymphocytes were enriched in natural killer (NK) cells and CD8+ T cells which are known to be the tumour-cytotoxic cells in IL-2-activated lymphocytes. However, there was no evidence of cytotoxicity towards the endothelial layer using a syngeneic model. The interaction of IL-2-activated lymphocytes and endothelial cells was not specific for high endothelium since equal numbers of activated lymphocytes bound to and migrated across aortic endothelium. The inability of IL-2-activated lymphocytes to discriminate between high endothelium and non-specialized 'flat' endothelium could be responsible for the widespread dissemination of the cells throughout the body following their adoptive transfer and the unwanted side-effects at non-involved sites.

High endothelial venule and immunocompetent cells in typical medullary carcinoma of the breast

The characteristics of immunocompetent cells and their role in killing tumour cells in typical medullary carcinoma of the breast (TMC) have been investigated morphologically. Formation of high endothelial venule (HEV)-like vessels in tumour cell nests, the distribution of macrophages, T-zone histiocytes, T- and B-lymphocytes, the ratios of CD4+/CD8+, and natural killer (NK) or NK-like T-cells were examined in five cases of TMC. These results were compared with controls which consisted of three cases of ductal carcinoma with intense lymphocytic infiltration (control I) and four cases of ductal carcinoma with scanty lymphocytic infiltration (control II). An increased incidence of HEV-like vessels with migration of lymphocytes and a higher number of CD8+ lymphocytes with interleukin-2-receptor expression, as well as numerous CD57 cells, were noted in the tumour nests of TMC as compared with those of control groups. Furthermore, large granular lymphocytes, large lymphocytes invaginating tumour cells and necrotic tumour cells were observed electron microscopically. These findings indicate that infiltrating lymphocytes in TMC are activated and become effector cells that can kill the tumour cells by mechanisms similar to those of NK cells. The activities of immunocompetent cells in TMC appear to contribute to a favourable prognosis in TMC of the breast.

Ultrastructural pathology of the 'barrier sites' in experimental autoimmune uveitis and experimental autoimmune pinealitis

Lewis rats were immunised with retinal S-antigen to induce experimental autoimmune uveitis and experimental autoimmune pinealitis. The blood-retinal and blood-pineal 'barrier sites' were examined by transmission electron microscopy. Inflammatory cell movement through Bruch's membrane involved separation of its constituent layers, cell migration through pores in the membrane, and between retinal pigment epithelial cells without causing significant displacement of the retinal pigment epithelial cell layer. The endothelial cells of retinal and pineal vessels with perivascular infiltrates showed morphological features resembling endothelium of 'high endothelial venules'.

Quantitative immunohistochemical analysis of mononuclear infiltrates in breast carcinomas--correlation with tumour differentiation

Inflammatory infiltrates were analysed in tissue sections of 76 breast carcinomas by counting the percentage of macrophages, IgA+ and IgG+ plasma cells, T cells with their subpopulations, and natural killer cells, and by measuring postcapillary venules (PCVs, found in 12 cases) within the infiltrates. These parameters were correlated with nuclear grade and biochemically determined hormone receptor status, known markers of tumour differentiation. A direct correlation was found between the extent of inflammation and nuclear grade (P less than 0.0001), and an inverse correlation between inflammation and oestrogen receptor (OR) positivity (P less than 0.05) as well as inflammation and progesterone receptor (PR) positivity (P less than 0.05). The percentage of the OKT8+ suppressor/cytotoxic T cells increased when the inflammation expanded from scanty to moderate (P less than 0.02). The diameter of the PCVs also increased with increasing inflammatory infiltrate (P less than 0.02). In addition, a direct correlation exists between the diameter of the PCVs and both the percentage of the OKT8+ T cells (P less than 0.04) and the Leu-7+ natural killer cells (P less than 0.03).

Mechanisms and regulation of lymphocyte migration

Lymphocyte traffic seems to be an essential requirement for an adequate immune response both in lymphoid tissues and local inflammatory sites. In this review, Adrian Duijvestijn and Alf Hamann discuss how selective migration of lymphocytes is directed by lymphocyte-endothelial interactions and what mechanisms may control this.

Human gamma interferon increases the binding of T lymphocytes to endothelial cells

Binding of lymphocytes to human umbilical vein endothelial cells (EC) was quantitated by measuring adhesion of 51Cr labelled lymphocytes to endothelial cell monolayers and rosette formation between lymphocytes and EC in suspension. Mitogen stimulated human peripheral blood mononuclear cell culture supernatants and mixed lymphocyte reaction supernatants enhanced the binding of T lymphocytes to EC monolayers or suspensions preincubated with such supernatants. The active component of these supernatants appeared to be gamma interferon (IFN-gamma) since culture supernatants lost activity after heating at 56 degrees C for 60 min, exposure to pH 2.0 or treatment with anti-IFN-gamma. In addition, purified IFN-gamma increased the binding of T lymphocytes to EC (T-EC). This occurred in a concentration dependent manner when IFN-gamma was preincubated with EC but not with lymphocytes. While the optimum concentration of IFN-gamma was 250 u/ml, a significant enhancement was seen with as little as 10 u/ml. These findings suggest that IFN-gamma may play a part in the emigration of lymphocytes to perivascular chronic inflammatory sites by augmenting the adhesion of lymphocytes to the endothelium of small blood vessels.

Relationship of tumor leucocytic infiltration to host defense mechanisms and prognosis

The interface between the tumor and the host is often the site of leucocytic infiltration. We will examine the idea that the infiltrating leucocytes of human and experimental tumors are components of the host immunological defense against the tumor, and that the presence of the infiltrate is a marker of favorable prognosis. Leucocytes could infiltrate tumors because of an active immune response, either nonspecific or specifically directed to tumor-associated antigens. Leucocyte influx may also occur because of chemotactic factors secreted by the tumor cells. Some tumors release factors which enhance vascular permeability and permit improved access by leucocytes to the tumor focus. The consequences of leucocytic infiltration include tumor cell cytolysis, cytostasis, or stimulation of proliferation. The present state of our knowledge of the interactions between tumor cells and infiltrating leucocytes precludes broad generalization of mechanisms. Further study will probably reveal that the mechanisms are diverse, and that there are some systems in which immune interactions occur at this interface and others in which they do not.

Changes in vascular endothelium related to lymphocyte collections in diseased synovia

A population of small blood vessels are described in the synovia of patients with a number of different arthropathies. These vessels are identical to the high endothelial venules (HEV) of lymph node paracortex, known to be the site of lymphocyte diapedesis from blood to tissues. The significance of this finding and its possible role in the pathogenesis of inflammatory arthritides are discussed.