Intercellular adhesion molecule-1 (ICAM-1) staining of reactive and neoplastic follicles. ICAM-1 expression of neoplastic follicle differs from that of reactive germinal center and is independent of follicular dendritic cells

Abstract

Background. Intercellular adhesion molecule‐1 (ICAM‐1) is expressed on follicular dendritic cells (FDC), and the ICAM‐1/LFA‐1 pathway is essential for affinity selection of activated B‐cells in germinal centers (GC). The expression of ICAM‐1 has been studied by immunostaining methods in GC, but not in neoplastic follicles (NF). Methods. The authors studied the expression of ICAM‐1 by the avidin‐biotin‐peroxidase complex (ABC) method with frozen sections in GC of reactive nodes (n = 22) and NF of follicular lymphomas (n = 19), in comparison with FDC staining. Results. GC stained uniformly for ICAM‐1, with staining intensity varying little from node to node, and follicular borders were well demarcated from the surroundings. Endothelial cells within GC did not stain whereas those outside stained strongly. In contrast, NF stained variably from tumor to tumor, and in any given tumor. Characteristically, follicular borders were not demarcated, and stained areas were difficult to define due to the lack of demarcation, with the exception of large cell type with diffuse areas (n = 2). Endothelium of intrafollicular vessels stained prominently (12 of 19), and appeared to contribute to the staining intensity of the follicles. FDC staining revealed a meshwork pattern in GC which was similar to that of ICAM‐1. The FDC meshwork pattern was present in 15 tumors. The pattern was remarkably uniform with sharply defined borders, which contrasted starkly to the variable staining and lack of follicular borders in the ICAM‐1 stain of the same tumors. Conclusions. The staining pattern of follicles for ICAM‐1 was similar to that for FDC in reactive nodes, but distinct from the latter in follicular lymphomas. An appropriate expression of ICAM‐1 appears to be essential for normal GC, as the alteration of the expression coincides with the malignant transformation of GC. The altered expression of ICAM‐1 may be useful in distinguishing NF from reactive GC.

Germinal Center Dendritic Cells Express More ICAM-1 Than Extrafollicular Dendritic Cells and ICAM-1/LFA-1 Interactions are Involved in the Capacity of Dendritic Cells to Induce PBMCs Proliferation

“…In our search to refine the immunophenotype of GCDCs allowing their identification in situ and their distinction from extrafollicular DCs, we found that CD54/ICAM-1 expression seemed to be a specific marker for GCDCs and was not detected on extrafollicular DCs. A few studies were devoted to the in situ immunolocalization of ICAM-1 in GC (Dustin et al 1986;Koopman et al 1991;Ree et al 1993). As with these authors, we found that GCs stained strongly and uniformly for ICAM-1.…”