Immune Events in Skin. I. Spontaneous Cluster Formation of Dendritic (Veiled) Cells and Lymphocytes from Skin Lymph

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Abstract
To investigate the mechanism of spontaneous attachment of afferent lymph lymphocytes to dendritic cells, cells from canine skin lymph were used. There were 3.3 +/- 2.8% of veiled cells in clusters found in lymph flowing from the cannulated lymph vessel. The number of clusters forming ex vivo in the collected lymph samples increased as a function of time and was temperature dependent. Incubation of cells with proteolytic enzymes or monosaccharides did not alter cell interactions. The ability of veiled cells to bind lymphocytes was independent of divalent cations but reduced by xylocaine and retinoic acid. Among steroids only methylprednisolone showed an inhibitory effect on cluster formation. Indomethacin and acetylsalicylic acid had no blocking activity on cell binding. Also, no effect was seen after treatment with cyclosporine A and azathioprine. An enhanced cluster formation after desialation with neuraminidase was observed. The desialated cells were cultured in order to study their stimulatory and accessory cell functions. No enhancement of autologous mixed leucocyte reaction was seen, but a significantly higher responsiveness to a suboptimal dose of phytohaemagglutinin was observed. The N-ase-mediated non-specific cell attachment could be abrogated by cell washing or treatment with EDTA or xylocaine. This study indicates that cluster formation by skin lymph veiled cells and lymphocytes is a spontaneous process which cannot be controlled by means usually effective in regulating the in vitro induced clustering of antigen-stimulated cells.