Dendritic cell/lymphocyte clustering: Morphologic analysis by transmission electron microscopy and distribution of gold‐labeled MHC class II antigens by high‐resolution scanning electron microscopy

Abstract

Dendritic cells (DCs) are potent antigen-presenting cells for a variety of immune responses; however, their mechanism of action has not been established. It is known that DCs can cluster with one another and with other cell types during in vitro immune responses, and clustering may be essential for the activation of resting lymphocytes. In this study, ultrastructural examination of clusters that form during extended culture of enriched rat splenic DCs (approximately 70% DCs) is reported. DCs were readily distinguished from other cell types, which included lymphocytes and macrophages. DCs displayed characteristic veils and/or dendritic processes that intertwined with processes of other cells within the cluster, or extended from the cluster periphery. Occasional DCs contained large vacuoles lined with small vesicles. A paramount feature of DCs is their constitutive expression of high levels of surface major histocompatibility complex class II antigens. The surface distribution of class II antigens on clustering DCs was examined using 10 nm immunogold labeling techniques and high-resolution scanning electron microscopy. DCs were readily distinguished by morphologic criteria, and examination of various surface membrane regions revealed a differential distribution of class II antigens. Gold label was frequently distributed in linear arrays and clusters, suggesting a cytoskeletal role in the recycling/redistribution of Class II antigens. These morphologic findings further an understanding of basic DC biology and their mechanism of action as antigen-presenting cells.

Detection of dendritic cells in the non-obese diabetic (NOD) mouse islet pancreas infiltrate is correlated with Th2-cytokine production

“…It is known that DCs accumulate at sites of infection or inflammation and can physically cluster with lymphocytes and with other DCs independent of MHC specificity [Inaba et al, 1984;Green and Jotte, 1985]. A striking feature of DCs is their constitutive expression of high levels of surface MHC class II antigens [Setum et al, 1993], which is confirmed in this study. In previous studies [Papaccio et al, 1994], it was demonstrated that infiltration occurring in NOD mice is a rather extensive and non specific process and which later undergoes a restriction.…”

The tetraspanin CD9 mediates lateral association of MHC class II molecules on the dendritic cell surface

“…MHC II molecules have been reported to cluster with each other and with MHC class I (12,13); ''superdimers'' were even observed in the original three-dimensional crystal structure of human MHC II (14). A few reports documenting surface MHC II dimer of dimers have followed, (15)(16)(17) but neither the significance nor specificity of these interactions has been established nor has their formation in physiological settings been demonstrated.…”

The common neoantigens in colorectal cancer are predicted and validated to be presented or immunogenic

“…Under inverted phase contrast microscope of 40× object lens, monocytes isolated from PBMCs were observed to display as small round cells, and gradually stretch and adhere the plastic surface of the culture plate on day1(Figure 3(a)). On day8 after the stimulation of a cytokine cocktail for two days, mature DCs were exhibited as irregularly large round and suspension cells with blunt, elongate dendritic processes as previously reported (Figure 3(a)) [27, 28]. Furthermore, the phenotype of mature DCs was analyzed by FACS testing the expression of co-stimulatory molecules and maturation markers.…”